METHODS AND SYSTEMS FOR DYE REMOVAL FROM POLYMER TEXTILES

Abstract

The present disclosure relates to a method that includes a first contacting of a starting solid composition that includes a starting solid phase and a dye with a removal fluid resulting in a first mixture that includes the starting solid phase, the dye, and the removal fluid, where the removal fluid includes at least one of a cyclic compound, a glycol, an alcohol, and/or an acid.

Claims

1. A method comprising: a first contacting of a starting solid composition comprising a starting solid phase and a dye with a removal fluid resulting in a first mixture comprising the starting solid phase, the dye, and the removal fluid, wherein the removal fluid comprises at least one of a cyclic compound, a glycol, an alcohol, or an acid.

2. The method of claim 1, wherein the removal fluid is biobased.

3. The method of claim 1, further comprising a first treating of the first mixture resulting in a recovered solid phase comprising the starting solid phase and an effluent comprising the dye.

4. The method of claim 3, further comprising a second treating of the effluent resulting in the separating and recovery of the dye and the removal fluid.

5. The method of claim 4, further comprising a second contacting of the recovered solid phase with an alcohol, resulting in a second recovered solid phase that has a concentration of the dye that is lower than a concentration of the dye for the recovered solid phase.

6. The method of claim 1, wherein the acid comprises at least one of acetic acid, levulinic acid, or n-valeric acid.

7. The method of claim 1, wherein the glycol comprises at least one of ethylene glycol or polyethylene glycol, propylene glycol, or polypropylene glycol.

8. The method of claim 1, wherein the cyclic compound comprises at least one of guaiacol, a guaiacol derivative, a phenol compound, cyrene, 7-valerolactone, -caprolactone, benzyl alcohol, or limonene.

9. The method of claim 8, wherein the guaiacol derivative comprises at least one of 4-ethylguaiacol, 4-propylguaiacol, eugenol, or isoeugenol.

10. The method of claim 8, wherein the phenol compound comprises at least one of phenol, 4-propyl phenol, thymol, 4-isopropylphenol, or 2-isopropylphenol.

11. The method of claim 1, wherein the alcohol comprises at least one of ethanol, isopropyl alcohol, n-butanol, 4-methyl-2-pentanol, or methanol.

12. The method of claim 1, wherein the starting solid phase comprises at least one of a synthetic material or a naturally occurring material.

13. The method of claim 12, wherein the synthetic material comprises at least one of a polymer, a resin, or an oligomer.

14. The method of claim 13, wherein the polymer comprises at least one of polyester, polyamide, polyurethane, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polychlorotrifluoroethylene, polyethylene terephthalate, polychloroprene, polyacrylonitrile, polytetrafluoroethylene, polyimide, or polybutylene adipate terephthalate.

15. The method of claim 1, wherein the starting solid phase is in a form comprising at least one of a fabric, fiber, pellet, powder, flake, granule, or film.

16. The method of claim 15, wherein the starting fiber has a diameter between 1.0 D and 2.2 D (Denier), or between 1.2 D and 2.0 D (Denier).

17. The method of claim 1, wherein the dye comprises at least one of a colorant, a pigment, a dyestuff, a stain, or a tincture.

18. The method of claim 1, wherein the dye comprises at least one of a natural dye or a synthetic dye.

19. The method of claim 18, wherein the natural or synthetic dye is ionic.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0009] Some embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than limiting.

[0010] FIG. 1 illustrates a method, according to some embodiments of the present disclosure.

[0011] FIGS. 2A and 2B illustrate a representation of a solid composition, with (FIG. 2A) and without a dye (FIG. 2B), according to some embodiments of the present disclosure.

[0012] FIG. 3 illustrates a schematic of an experimental procedure used to test the feasibility of the method illustrated in FIG. 1, according to some embodiments of the present disclosure.

[0013] FIG. 4 illustrates polyethylene terephthalate (PET) patches tested using a method similar to that illustrated in FIG. 3, according to some embodiments of the present disclosure.

[0014] FIG. 5 illustrates the chemical structures and names of biobased removal fluids (i.e., solvents) screened for the ability to treat the PET patches illustrated in FIG. 4, according to some embodiments of the present disclosure.

[0015] FIG. 6 illustrates photographs of the PET patches illustrated in FIG. 4, after treatment using the procedure illustrated in FIG. 3, according to some embodiments of the present disclosure. (Solvents tested: 4-propylphenol (4-PP), 4-propylguaiacol (4-PG), 4-ethylguaiacol (4-EG), acetic acid (AA), diethylene glycol monoethyl ether (DE))

[0016] FIGS. 7A-7D illustrate photographs of PET fabrics: (FIG. 7A) untreated, and dye extracted (FIG. 7B) jersey (FIG. 7C) woven and (FIG. 7D) fleece samples in bio-based solvents, acetic acid (AA), 4-ethylguaiacol (4-EG), 4-propylguaiacol (4-PG), and 4-propylphenol (4-PP), according to some embodiments of the present disclosure.

[0017] FIG. 8 illustrates optical micrographs of PET fabrics (jersey-blue (JBl)top row and woven-black (WB))bottom row, after dye extraction in bio-based solvents, acetic acid (AA), 4-ethylguaiacol (4-EG), 4-propylguaiacol (4-PG), and 4-propylphenol (4-PP), according to some embodiments of the present disclosure.

[0018] FIG. 9 illustrates concentration-dependent dye extraction from PET fabrics (jersey-red (JR), woven-black (WB), and fleece-black (FB)) using 4-ethylguaiacol (4-EG) as the extraction solvent, according to some embodiments of the present disclosure.

[0019] FIGS. 10A-10C illustrate weight loss values of PET fabrics (jersey-red (JR), woven-black (WB), and fleece-black (FB)) using 4-ethylguaiacol (4-EG) in different extraction conditions, (FIG. 10A) temperature, (FIG. 10B) concentration (the ratio of fabric to solvent), and (FIG. 10C) operating time, according to some embodiments of the present disclosure.

[0020] FIG. 11 illustrates percent weight loss results of the PET patches illustrated in FIG. 4, after treatment using the procedure illustrated in FIG. 3, according to some embodiments of the present disclosure. (4-propylphenol (4-PP), 4-propylguaiacol (4-PG), 4-ethylguaiacol (4-EG), acetic acid (AA), diethylene glycol monoethyl ether (DE))

[0021] FIGS. 12A-12C illustrate GPC traces of recovered PET fabrics (FIG. 12A) jersey red (JR), (FIG. 12B) woven black (WB), and (FIG. 12C) fleece black (FB)) after dye extraction in bio-based solvents, acetic acid (AA), 4-ethylguaiacol (4-EG), 4-propylguaiacol (4-PG), and 4-propylphenol (4-PP), according to some embodiments of the present disclosure.

[0022] FIGS. 13A-13D illustrate color measurements of PET fabrics (jersey red (JR), woven black (WB), and fleece black (FB)) after dye extraction in bio-based solvents, acetic acid (AA), 4-ethylguaiacol (4-EG), 4-propylguaiacol (4-PG), and 4-propylphenol (4-PP), according to some embodiments of the present disclosure. In the CIELAB color space, L* represents lightness (FIG. 13A), a* stands for red and green value (FIG. 13B), and b* stands for yellow and blue (FIG. 13C). Delta E (dE) is the color difference between the greige and the sample in an L*a*b* color space (FIG. 13D).

[0023] FIGS. 14A-14D illustrate color measurements of PET fabrics (jersey-red (JR), jersey-blue (JB), jersey-green (JG), woven-black (WB), woven-orange (WO), woven-green (WG), fleece-black (FB), and fleece-grey (FG)) after dye extraction in bio-based solvents, 1acetic acid (AA), 24-ethylguaiacol (4-EG), 34-propylguaiacol (4-PG), and 44-propylphenol (4-PP), according to some embodiments of the present disclosure. In the CIELAB color space, L* represents lightness (FIG. 14A), a* stands for red and green value (FIG. 14B), and b* stands for yellow and blue (FIG. 14C). Delta E (dE) is the color difference between the greige and the sample in an L*a*b* color space (FIG. 14D).

[0024] FIG. 15 illustrates photographs of (top) extracted dye solutions in acetic acid and (bottom) PET fabrics in different stages, (Panel A) untreated, (Panel B) dye-extracted, and (Panel C) re-dyed PET fabrics, according to some embodiments of the present disclosure. Note that the re-dyeing process was performed by a commercial exhaust dyeing method for polyester using auxiliary chemicals and the dyes extracted from the untreated fabrics.

[0025] FIG. 16 illustrates photographs of dye-extracted solutions with different PET fabrics (jersey-red (JR), jersey-blue (JB), jersey-green (JG), woven-black (WB), woven-orange (WO), woven-green (WG), fleece-black (FB), and fleece-grey (FG)) using bio-based solvents (from left to rightacetic acid (AA), 4-ethylguaiacol (4-EG), 4-propylguaiacol (4-PG), and 4-propylphenol (4-PP)), according to some embodiments of the present disclosure. Note that 4-EG and 4-PP have yellow hues as their intrinsic colors which affected the colors of the dye solutions.

[0026] FIG. 17 illustrates temperature-dependent dye extraction from PET fabrics (jersey-red (JR), woven-black (WB), and fleece-black (FB)) using 4-ethylguaiacol (4-EG) as the extraction solvent, according to some embodiments of the present disclosure.

[0027] FIG. 18 illustrates operating time-dependent dye extraction from PET fabrics (jersey-red (JR), woven-black (WB), and fleece-black (FB)) using 4-ethylguaiacol (4-EG) as the extraction solvent, according to some embodiments of the present disclosure.

[0028] FIGS. 19A-19C illustrate GPC traces of recovered PET fabrics (jersey red (JRFIG. 19A), woven black (WBFIG. 19B), and fleece black (FBFIG. 19C)) after dye extraction using 4-ethylguaiacol (4-EG) at different temperatures, according to some embodiments of the present disclosure.

[0029] FIGS. 20A-20E illustrate thermal properties of recovered PET fabrics (jersey red (JR), woven black (WB), and fleece black (FB)) after dye extraction using 4-ethylguaiacol (4-EG) at different temperatures, (FIG. 20A) melting temperatures, (FIG. 20B) % crystallinity, (FIGS. 20C-20E) thermal degradation behaviors of the fabrics, according to some embodiments of the present disclosure. Note that DSC (FIGS. 20A and 20B) and TGA (FIGS. 20C-20E) were used for the measurements.

[0030] FIGS. 21A-21F illustrate thermal properties of recovered PET fabrics (Jersey-red (JR), Jersey-blue (JB), Jersey-green (JG), Woven-black (WB), Woven-orange (WO), Woven-green (WG), Fleece-black (FB), and Fleece-grey (FG)) after dye extraction in bio-based solvents (acetic acid (AA), 4-ethylguaiacol (4-EG), 4-propylguaiacol (4-PG), and 4-propylphenol (4-PP)), according to some embodiments of the present disclosure: (FIG. 21A) thermal properties of initial fabric materials, (FIG. 21B) melting temperatures, (FIG. 21C) % crystallinity, (FIGS. 21D-21F) thermal degradation behaviors of the fabrics. Note that DSC (FIGS. 21A-21C) and TGA (FIGS. 21D-21F) were used for the measurements.

[0031] FIGS. 22A and 22B illustrate organic solvent nanofiltration (OSN) experiment results, according to some embodiments of the present disclosure. FIG. 22A illustrates permeabilities of the acetic acid and dye rejection rates of BORSIG oNF-2 membranes. Seven disperse dyes were evaluated, including Jersey-blue (JBl), Jersey-red (JR), Jersey-green (JG), Woven-black (WB), Woven-orange (WO), Fleece-grey (FGr), and Fleece-black (FB). Photos of the permeate (left) and the feed (right) of each dye sample are shown under each column. FIG. 22B illustrates dye removal rates of Jersey-blue and Woven-black as a function of the number of complete membrane passes. The volume of the starting feed solution was 300 ml and the applied pressure was 500 psi. Photos of feed and permeate solutions at each stage are shown near the corresponding data point.

[0032] FIGS. 23A-23H illustrate data for dyes from Jersey Red, Jersey Blue, Jersey Green, and Woven Black, where FIGS. 23A, 23C, 23E, and 23G illustrate CCC chromatograms of separating specific dyes using an HCMWat (3/1/3/1) solvent system in the reverse phase (lower mobile phase) and FIGS. 23B, 23D, 23F, and 23H illustrate LC-MS data of the extracted dye and collected CCC effluent fractions labeled in FIGS. 23A, 23C, 23E, and 23G, according to some embodiments of the present disclosure. [M+H] values provided were compounds with strong responses in the visible range.

[0033] FIG. 24 illustrates a flow-through system for extracting dyes from dyed fabrics, according to some embodiments of the present disclosure.

[0034] FIGS. 25A-25C illustrate three extraction temperature profiles that were targeted for operating the flow-through system illustrated in FIG. 23A, for dye removal from dyed fabrics, according to some embodiments of the present disclosure.

[0035] FIG. 26 illustrates (top) the dyed fabrics, before and after treatment in the flow-through reactor, and the (bottom) resultant dyes extracted from the treated fabrics, using the flow-through system illustrated in FIG. 23A, according to some embodiments of the present disclosure.

[0036] FIG. 27 illustrates GPC data obtained from the fabric, before and after treatment, resulting from the three temperature profiles (see FIGS. 25A-25C) when operating the flow-through system (see FIG. 24), according to some embodiments of the present disclosure.

[0037] FIG. 28 illustrates DSC obtained from the fabrics, for the original undyed starting fabric and after treating the dyed fabric with the three temperature profiles using the flow-through system, according to some embodiments of the present disclosure.

[0038] FIG. 29 illustrates TGA data obtained from the fabrics, for the original undyed starting fabric and after treating the dyed fabric with the three temperature profiles using the flow-through system, according to some embodiments of the present disclosure.

REFERENCE NUMERALS

[0039] 100 . . . method [0040] 110 . . . contacting [0041] 111 . . . starting solid composition [0042] 112 . . . starting solid phase [0043] 113 . . . dye [0044] 114 . . . removal fluid [0045] 116 . . . first mixture [0046] 120 . . . first treating [0047] 121 . . . recovered solid phase [0048] 122 . . . effluent [0049] 130 . . . second treating [0050] 131 . . . recovered dye [0051] 132 . . . recovered removal fluid

DETAILED DESCRIPTION

[0052] The embodiments described herein should not necessarily be construed as limited to addressing any of the particular problems or deficiencies discussed herein. References in the specification to one embodiment, an embodiment, an example embodiment, some embodiments, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0053] As used herein the term substantially is used to indicate that exact values are not necessarily attainable. By way of example, one of ordinary skill in the art will understand that in some chemical reactions 100% conversion of a reactant is possible, yet unlikely. Most of a reactant may be converted to a product and conversion of the reactant may asymptotically approach 100% conversion. So, although from a practical perspective 100% of the reactant is converted, from a technical perspective, a small and sometimes difficult to define amount remains. For this example of a chemical reactant, that amount may be relatively easily defined by the detection limits of the instrument used to test for it. However, in many cases, this amount may not be easily defined, hence the use of the term substantially. In some embodiments of the present invention, the term substantially is defined as approaching a specific numeric value or target to within 20%, 15%, 10%, 5%, or within 1% of the value or target. In further embodiments of the present invention, the term substantially is defined as approaching a specific numeric value or target to within 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1% of the value or target.

[0054] As used herein, the term about is used to indicate that exact values are not necessarily attainable. Therefore, the term about is used to indicate this uncertainty limit. In some embodiments of the present invention, the term about is used to indicate an uncertainty limit of less than or equal to 20%, 15%, 10%, 5%, or 1% of a specific numeric value or target. In some embodiments of the present invention, the term about is used to indicate an uncertainty limit of less than or equal to 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1% of a specific numeric value or target.

[0055] The present disclosure relates to methods, systems, and materials for removing dyes from colored fabrics including, for example, colored polyester fabrics in different forms such as knit, woven, and/or fleece using biobased solvents. Examples of biobased solvents for such processing and separation of dyes from solid fabrics include at least one of a guaiacol and/or a guaiacol derivative, a phenol-containing molecule, and/or a carboxylic acid. Specific examples include 4-ethylguaiacol, 4-propylguaiacol, 4-propylphenol, and/or acetic acid. As shown herein, such solvents can be effective at dissociating, for example dissolving, one or more dye components, without changing the properties of the starting solid, e.g., polymer fabrics, while also having the advantage of being less hazardous than conventional organic solvents used for plastic dissolution. As described herein, in some embodiments of the present disclosure, a method for separating a dye from its associated solid phase may include immersion of the starting dye/solid composition in a biobased solvent at relatively low temperatures, e.g., 100 C. or less. In some embodiments of the present disclosure, immersion temperatures may be selected that are above the glass transition temperature of the solid polymer phase, e.g., polyethylene terephthalate (PET), which enables the polymer to swell, which may facilitate the release of dyes from their associated solid polymer phase into the liquid biobased solvent. The resulting dye-free solid polymer phase, e.g., PET, and the recovered dyes may then be recycled for reuse. Further, in some embodiments of the present disclosure, the biobased solvent(s) may be recovered and recycled.

[0056] FIG. 1 illustrates an exemplary method for treating a fabric and/or textile that includes a solid phase and a dye, resulting in the separation and recovery of the solid phase and the dye, thereby enabling their recycle and reuse for the manufacture of new fabrics and/or textiles. Referring to FIG. 1, this exemplary method 100 for recovering the solid phase and the dye includes at least three steps, which as shown, may be completed sequentially (in series). The method 100 may result in the formation of at least three recovered materials, a recovered solid phase 121 (e.g., dye-free PET), recovered dye 131, and recovered removal fluid 132 (e.g., recovered biobased solvent). The production of these materials may enable the recovery and reuse of the recovered solid phase 121 and the recovered dye 131, and the recovery, recycle, and reuse of the removal fluid 132 (e.g., recycled to the contacting 110 step), thereby providing a method for dye removal from end-of-life textiles and fabrics that is more environmentally friendly and economically viable than incumbent technologies.

[0057] FIG. 2A illustrates a starting solid composition 111 (e.g., polymer), that includes a starting solid phase 112 in combination with a dye 113. The dark shade of the starting solid phase 112 indicates the presence of the dye 113 on the external surfaces and encapsulated within the structure of the starting solid phase 112. FIG. 2B illustrates a recovered solid phase 121, after the dye 113 has been removed from the starting solid phase 112. This absence of dye 113 is indicated by the lighter shade of the recovered solid phase 121, relative to the starting solid phase 112 illustrated in FIG. 2A. Note that a starting solid composition 111 may include other components and additives, such as at least one of a fixative, a mordant, a UV-absorbent, a water repellent, an anti-odor additive, an antioxidant, an optical brightener, and/or a processing aid. The methods described herein may also be effective at separating, removing, and recovering such components and/or additives, in addition to the starting solid phase 112 and the dye 113, thereby enabling the reuse of the recovered components and/or additives.

[0058] Referring again to FIG. 1, the exemplary method 100 for separating a dye 113 from a starting solid phase 112 may begin with a contacting 110 of the starting solid composition 111 (e.g., the starting dyed textile) with a removal fluid 114 (e.g., a biobased solvent). The contacting 110 of the starting solid composition 111 with the removal fluid 114 may result in the formation of a first mixture 116, which includes the combination of the starting solid composition 111 with the removal fluid 114. In some embodiments of the present disclosure, the contacting 110 may include wetting and/or immersing the starting solid composition 111 in the removal fluid 114. When immersing the starting solid composition 111 in the removal fluid 114, a slurry may be formed when the starting solid composition 111 is not soluble in the removal fluid 114. The contacting 110 of the starting solid composition 111 with the removal fluid 114 may be achieved using various unit operations and operating conditions, which may depend on the specific materials being treated and their forms, shapes, particle sizes, etc. Some of these are discussed in more detail below and include stirred tank reactors and packed bed reactors, which may be configured in batch, continuous, and/or semi-continuous figurations.

[0059] An objective of the contacting 110 is to separate the starting solid phase 112 (FIG. 2A) from the dye 113, thereby providing an essentially dye-free solid phase (FIG. 2B) dispersed within a dye-rich removal fluid phase. Once this has been achieved to a satisfactory level, the mixture of a dye-free solid dispersed within a dye-rich removal fluid may be transferred to a first treating 120, the objective of which may include the physical separating of the starting textile/fabric's solid phase from the dye. For example, when the contacting 110 involves immersing the starting solid composition 111 in the removal fluid 114 (e.g., biobased solvent), the resultant first mixture 116 may be directed to a first treating 120 that may include a unit operation that physically separates the solid phase from the liquid phase. Thus, a first treating 120 may result in a recovered solid phase 121 of essentially dye-free solid (e.g., polymer) and an effluent 122 of essentially solid-free, dye-rich removal fluid. In some embodiments of the present disclosure, the physical separation of a solid phase from a liquid effluent rich in dye may be achieved by configuring the first treating 120 to use at least one of a filtration unit and/or a centrifugation unit.

[0060] Referring again to FIG. 1, once the recovered solid phase 121 has been separated from the dye, the dye-rich-liquid phase, the effluent 122, may be directed to a second treating 130 that may be configured to separate the dye 113 from the removal fluid 114, resulting in recovered dye 131 and recovered removal fluid 132. Again, this second treating 130 may enable the recovery of both the dye 113 and the removal fluid 114, enabling their reuse, thereby minimizing the quantity of material released into the environment. For example, a second treating 130 may include one or more unit operations that include at least one of distillation, liquid-liquid extraction, crystallization, absorption, adsorption, counter-current chromatography (CCC), membrane filtration, and/or an ion exchange membrane separation.

[0061] In some embodiments of the present disclosure, a method like that illustrated in FIG. 1 may include one or more pre-treatment steps and/or post-treatment steps. For example, in some embodiments of the present disclosure, the recovered solid phase 121 resulting from a first treating 120 (e.g., filtration) may be washed with a solvent, e.g., an alcohol. This may be performed, for example, if the recovered solid phase 121 still contains an appreciable amount of dye. Such a washing step (not shown in FIG. 1) may result in an additional recovered dye and a second recovered solid phase having less dye than that of the recovered solid phase 121 from the first treating 120.

[0062] In some embodiments of the present disclosure, a starting solid composition 111 may be pretreated before a contacting 110 step and/or a first treating 120 step. For example, a pretreating step (not shown) may include a size reduction step, where a textile and/or fabric containing object is reduced from a first size and/or shape to a different final size and/or shape. For example, in some embodiments of the present disclosure, a textile/fabric containing object may be reduced in size and/or have its shape changed by passing it through a size-reducing unit operation, that shreds, cuts, and/or tears the object. In some embodiments of the present disclosure, this may be achieved using a knife-mill, a hammer-mill, and/or any other suitable device/system. In some embodiments of the present disclosure, textile-containing objects may be shredded, reduced in size, to a confetti like shape and density, having a characteristic length and width between 0.01 cm by 0.01 cm and 10.0 cm by 10.0 cm or between 0.1 cm by 0.1 cm and 1.0 cm by 1.0 cm. In some embodiments of the present disclosure, the starting solid phase 111 may be in a form that includes at least one of a fiber, a yarn, a fabric, a sheet, a swatch, a pellet, a powder, a flake, a granule, and/or a film. For the example of a starting solid composition 111 being in the form of a fiber and/or yarn, fibers and yarns may have a diameter between 1.0 D and 2.2 D (Denier), or between 1.2 D and 2.0 D.

[0063] Referring again to FIG. 1, now with the method generally described, some additional specifics, embodiments, examples, etc., will be described. As described above, in some embodiments of the present disclosure, a removal fluid 114 may be a biobased solvent. Whether a removal fluid 114 is bioderived (i.e., biobased), or at least partially bioderived may be determined by ASTM-D6866. In some embodiments of the present disclosure, a biobased solvent for removing a dye from a solid phase may include at least one of a cyclic compound, a glycol, an alcohol, and/or an acid. Examples of acids that may be used as a removal fluid include at least one of acetic acid, levulinic acid, and/or n-valeric acid. Examples of glycols that may be used as a removal fluid include at least one of ethylene glycol, polyethylene glycol, propylene glycol, and/or polypropylene glycol. Examples of cyclic compounds that may be used as a removal fluid include at least one of guaiacol, a guaiacol derivative, a phenol compound, cyrene, -valerolactone, -caprolactone, benzyl alcohol, and/or limonene. Examples of guaiacol derivatives that may be used as a removal fluid include at least one of 4-ethylguaiacol, 4-propylguaiacol, eugenol, and/or isoeugenol. Examples of phenols that may be used as a removal fluid include at least one of phenol, 4-propyl phenol, thymol, 4-isopropylphenol, and/or 2-isopropylphenol. Examples of alcohols that may be used as a removal fluid include at least one of ethanol, isopropyl alcohol, n-butanol, 4-methyl-2-pentanol, and/or methanol.

[0064] In some embodiments of the present disclosure, a removal fluid 114 suitable for separating a solid phase (e.g., PET fabric) from a dye may be characterized by at least one physical property and/or performance metric. Examples include water solubility (g removal fluid/L of water), flash point, melting point, boiling point, and/or a toxicity value. For example, in some embodiments of the present disclosure, a removal fluid may have a water solubility between substantially immiscible with water and substantially soluble in water, approaching or equal to completely soluble in water. In some embodiments of the present disclosure, a removal fluid may have a water solubility between 1 gram removal fluid per liter of water (g/L) and 603 g/L. In some embodiments of the present disclosure, a removal fluid may have a flash point between 10 C. and 230 C. or between 40 C. and 113 C. In some embodiments of the present disclosure, a removal fluid may have a boiling point between 65 C. and 290 C. or between 117 C. and 236 C. In some embodiments of the present disclosure, a removal fluid may have a LD50 oral toxicity between 348 mg/kg and 22,000 mg/kg or between 348 mg/kg and 3,310 mg/kg. In some embodiments of the present disclosure, a removal fluid may have a LD50 dermal toxicity between 660 mg/kg and 6400 mg/kg or between 1100 mg/kg and 3310 mg/kg. In some embodiments of the present disclosure, a removal fluid may have a melting point between 150 C. and 63 C. or between 6 C. and 22 C.

[0065] Solvents (i.e., removal fluids) that can be attained using renewable bioderived sources are preferable for a variety of reasons. All of the top-performing solvents described herein may be bioderived. For example, 4-ethylguaiacol can be produced by pyrolysis of lignocellulosic biomass. It is produced from the lignin, along with many of the other phenolic compounds present in bio-oil. In particular, 4-ethylguaiacol is derived from guaiacyl in the lignin. Biobased acetic acid can be derived from biomass via extraction using ethyl acetate. Or bio based acetic acid can be produced by refining bioethanol (derived from corn or other starch crops).

[0066] A variety of fabrics, textiles, and/or other starting solid compositions may be treated using the methods and systems described herein, including compositions having starting solid phases that are constructed using synthetic materials and/or a naturally occurring materials. Examples of synthetic materials include at least one of a polymer, a resin, and/or an oligomer. Examples of polymers for a starting solid phase include at least one of a polyester, a polyamide, a polyamine, a polyurethane, and/or a polyolefin. Specific examples of polymers that may be treated according to the methods described herein include at least one of polyethylene, polypropylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polychlorotrifluoroethylene, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polychloroprene, polyacrylonitrile, polytetrafluoroethylene, polyimide, and/or polybutylene adipate terephthalate. Examples of oligomers for a starting solid phase include oligomers of any of the polymers listed above, e.g., oligomers of at least one of a polyester, a polyamide, a polyamine, a polyurethane, and/or a polyolefin.

[0067] Naturally occurring materials that may provide the starting solid composition 111 in a fabric that may be treated using the methods and systems described herein include starting solid phases constructed using at least one of lignin, cellulose, and/or hemicellulose. Further, naturally occurring materials may include at least one of a plant-based material and/or an animal-based material. Examples of plant-based materials are materials (e.g., fibers) that include at least one of cotton, hemp, coir, linen, ramie, sisal, jute, kapok, and/or ramina and/or materials derived therefrom. Examples of animal-based material are materials (e.g., fibers) derived from at least one of alpaca, Angora rabbit, Angora goat, Kashmir goat, sheep, camel, and/or silkworm.

[0068] In some embodiments of the present disclosure, a starting solid phase, e.g., naturally occurring and/or synthetic, a polymer and/or oligomer, etc., may be characterized by at least one of a physical property and/or a performance metric, such as at least one of a melting point, a percent crystallinity, a degradation temperature, a molecular weight, and/or polydispersity. For example, a starting solid phase may be characterized by a melting point between 230 C. and 270 C. or between 245 C. and 253 C. In some embodiments of the present disclosure, a starting solid phase may be characterized by a percent crystallinity between 20% and 60% or between 35% and 42%. In some embodiments of the present disclosure, a starting solid phase may be characterized by a degradation temperature, corresponding to about 5 wt % loss, between 350 C. and 450 C. or between 400 C. and 410 C. In some embodiments of the present disclosure, a starting solid phase may be characterized by a molecular weight (M.sub.nnumber average) between 15,000 Da and 26,000 Da or between 18,000 Da and 21,000 Da. In some embodiments of the present disclosure, a starting solid phase may be characterized by a molecular weight (M.sub.wweight average) between 30,000 Da and 40,000 Da or between 34,000 Da and 35,000 Da. In some embodiments of the present disclosure, a starting solid phase may be characterized by a polydispersity (PDI) between 1.4 and 2.3 or between 1.7 and 1.9.

[0069] A dye used to color a starting solid phase (to form a starting solid composition) may include any suitable dye for a particular use and/or fabric, textile, and/or garment being colored, with examples of dyes including colorants, pigments, dyestuffs, stains, and/or tinctures. Further, a dye as described herein may be a natural dye and/or a synthetic dye. In some embodiments of the present disclosure, a natural dye may be ionic. In some embodiments of the present disclosure, a synthetic dye may include at least one of an acid dye, a basic dye, an ionic dye, a direct dye, an azo dye, an anthraquinone dye, an indigo dye, a phthalocyanine dye, a nitro dye, a nitroso dye, a disperse dye, a vat dye, a mordant dye, a reactive dye, a solvent dye, and/or a sulfur dye.

[0070] Referring again to FIG. 1, the method 100 is illustrated for exemplary purposes, and is not intended to be limiting. For example, the individual steps, e.g., contacting 110, first treating 120, and second treating 130 are shown as occurring separately and in series. However, in some embodiments of the present disclosure, one or more steps may be combined to occur in a single step. For example, in some embodiments of the present disclosure, the contacting 110 and at least one of the first treating 120 and/or the second treating 130 may occur substantially in parallel in a single step or unit operation. For example, the contacting 110 and the first treating 120 may be performed substantially simultaneously in a Soxhlet extraction-like unit and/or in an extraction centrifugation unit. Further, in some embodiments of the present disclosure, methods for separating a dye from the solid phase of a starting solid composition may include fewer or more steps than those illustrated in FIG. 1. Other methods that may be configured to combine processing steps and/or used in addition to those illustrated in FIG. 1 include microwave assisted extraction (MAE) and/or accelerated solvent extraction (ASE). MAE applies microwaves that will assist in opening polymer crystalline domains in fibers to release more dyes. ASE applies high temperature and pressure to induce more molecule motion and open crystalline regimes in polymeric fibers to release more dye molecules.

[0071] Systems for performing methods like that illustrated in FIG. 1 may be completed using a variety of chemical engineering unit operations, which may vary depending on the specific process requirements and/or materials being separated. For example, a first contacting 110 may be performed using any suitable unit operation, e.g., device, designed to intimately mix and contact the starting solid composition 110 with the removal fluid 114. For example, in some embodiments of the present disclosure, a first contacting 110 may be performed using a stirred tank reactor, which may be batch and/or continuous. In some embodiments of the present disclosure, a stirred tank reactor for performing a first contacting 110 may be a continuous reactor having two or more stages. In some embodiments of the present disclosure, a first contacting 110 may be performed using at least one of a mixer, an agitator, and/or ultrasound. A first contacting 110 may be performed using a mixer and/or an agitator operated at between 200 rpm and 500 rpm. In some embodiments of the present disclosure a first contacting 110 may be achieved using a packed bed reactor, where a starting solid composition 111 is positioned within the packed bed reactor and the removal fluid 114 is directed to the packed bed reactor, such that the removal fluid 114 contacts and flows over the starting solid composition 111. This may be achieved in a semi-continuous fashion. For example, two packed bed reactors may be provided, whereas one is online containing a starting solid composition 111 that is being contacted by a removal fluid 114, a second is offline and being emptied of the recovered solid phase 121 and refilled with fresh starting solid composition 111.

[0072] As described above, in some embodiments of the present disclosure, a mixture 116 resulting from a first contacting 110 may be directed to a first treating 120 configured to separate the solid phase, now substantially free of a dye bound to its surface, thereby forming a recovered solid phase 121 and an effluent 122 that includes the dye 113 and the removal fluid 114. For example, such a separating of the solid phase from the liquid effluent may be achieved using filtration, centrifugation, and/or a gravimetric method (e.g., separation due to density differences between the solid phase and liquid phase). As described above, in some embodiments of the present disclosure, such a separation step, i.e., first treating 120 may be achieved in the same unit operation used to perform the first contacting 110, for example in a CSTR and/or in a spinning-basket device. This may be achieved by designing a CSTR to allow the gravimetric separation of the solid phase from the liquid phase, such that the solid phase may either overflow a baffle (when the light phase) or pumped from the bottom of a CSTR (when the heavy phase). A single CSTR may be utilized to accomplish this, e.g., a one stage contacting and separating, or two or more CSTRs may be positioned in series, for multi-stage contacting and separating. For a multi-stage arrangement, each subsequent stage may add more removal fluid 114 and/or fresh starting solid composition 111 and/or dye-rich effluent may be removed, as needed to optimize any number of design metrics; e.g., operating costs, capital costs, removal efficiencies, etc. In some embodiments of the present disclosure, a first contacting 110 may be achieved using one, two, three, or four CSTRs positioned in series. In some embodiments of the present disclosure, a first contacting 110 may be achieved using at least one packed bed reactor, as described above.

[0073] In some embodiments of the present disclosure, a first contacting 110 may be performed at a temperature above the glass transition temperature of the starting solid phase 112 of the starting solid composition 111 being mixed with a removal fluid 114 in the first contacting 110. For example, a first contacting 110 may be performed at a temperature between 90 C. and 200 C., or between 90 C. and 150 C. In some embodiments of the present disclosure, a first contacting 110 may be performed for a period of time between 10 minutes and 12 hours. Among other things, by mixing at an elevated temperature, e.g., above ambient temperature, the starting solid phase 112 of a starting solid composition 111 may soften and/or expand the polymer and/or weaken the non-covalent bonds holding the starting solid phase 111 and the dye 111, thereby enabling the removal fluid 114 to more easily separate the dye 113 from the starting solid phase 112.

[0074] Referring again to FIG. 1, in some embodiments of the present disclosure, for example when a first contacting 110 simply contacts (but does not separate) a solid phase from a liquid phase, the resultant first mixture 116 may be directed to a first treating 120 that is configured to complete this separation. For example, a first treating 120 may be performed by directing the first mixture 116 to at least one of a filtration unit and/or a gravitational unit, resulting in the forming of a recovered solid phase 121 and an effluent 122 that includes the removed dye in the removal fluid. In some embodiments of the present disclosure, the separating of the solid phase from the liquid phase may include a filtration unit using at least one of a membrane filter and/or a rotating ceramic filter. For the case of a membrane filter, the filter may be constructed using at least one of polypropylene (PP), polyethersulfone (PES), and/or polytetrafluoroethylene (PTFE), having a plurality of pores with an average pore size of less than or equal to 1 m or less than or equal to 0.2 m. Gravitational methods may include a settling tank. In some embodiments of the present disclosure a first treating 120 may utilize a centrifuge.

[0075] As described above, in some embodiments of the present disclosure, a method 100 may include a second contacting (not shown in FIG. 1), for example as a washing step, to remove any residual dye 113 that may still adhere to the recovered solid phase 121 resulting from one or more contacting 110 steps. For example, a recovered solid phase 121 may be contacted with a liquid, e.g., solvent, at about room temperature for period of time that is less than five minutes. In some embodiments of the present disclosure, such a solvent may include an alcohol. As a result of the second contacting (not shown), the resultant solid/solvent mixture may then proceed to a separating step configured to separate the washed solid phase into a second recovered solid phase (not shown) from the solvent, e.g., alcohol. For example, a second contacting (not shown) may be configured to include drying the second recovered solid phase, thereby removing the liquid, e.g., alcohol, to produce a dried second recovered solid phase (not shown). In some embodiments of the present disclosure, drying of the second recovered solid phase may be achieved at a temperature of at least 100 C., at a pressure near or below atmospheric pressure, for a period of time between one 1 minute and three days or between 1 hour and 24 hours. The dried recovered solid phase may then be recycled to produce new products, e.g., fibers, textiles, and/or garments. Further, in some embodiments of the present disclosure, steam may be used to displace a solvent from a recovered solid phase 121, which may then be followed by a drying step to remove water from the solid phase.

[0076] Referring again to FIG. 1, in some embodiments of the present disclosure, an effluent 122 containing the dye 113 resulting from at least one of a contacting 110 and/or a first treating 120 may be directed to a second treating 130 configured to separate at least a portion of the dye 113 from the removal fluid 114. As a result, such a second treating 130 may produce recovered dye 131 and recovered removal fluid 132, thereby enabling the recovery and reuse of at least one of the dye 113 and/or the removal fluid 114. For example, the recovered dye may be used to color the recovered solid phase and/or new virgin polymers, oligomers, and/or fibers. Further, the recovered removal fluid may be recycled to the contacting 110, thereby minimizing and/or eliminating the need for a fresh, make-up stream of removal fluid. In some embodiments of the present disclosure, a second treating 130 may be performed using at least one of absorption, adsorption, evaporation, distillation, physical separation, crystallization, precipitation, and/or chromatography. In some embodiments of the present disclosure, a chromatographic method for separating dye from a removal fluid may include at least one of flash column chromatography, counter-current chromatography (CCC), and/or ion chromatography.

[0077] Whether or not a reactant or product described herein is bioderived and/or biobased may be determined by analytical methods. Using radiocarbon and isotope ratio mass spectrometry analysis, the biobased content of materials can be determined. ASTM International, formally known as the American Society for Testing and Materials, has established a standard method for assessing the biobased content of carbon-containing materials. The ASTM method is designated ASTM-D6866. The application of ASTM-D6866 to derive a biobased content is built on the same concepts as radiocarbon dating, but without use of the age equations. The analysis is performed by deriving a ratio of the amount of radiocarbon (14C) in an unknown sample to that of a modern reference standard. The ratio is reported as a percentage with the units pMC (percent modern carbon). If the material being analyzed is a mixture of present-day radiocarbon and fossil carbon (containing no radiocarbon), then the pMC value obtained correlates directly to the amount of biomass material present in the sample. Thus, ASTM-D866 may be used to validate that the compositions described herein are derived from renewable, biobased sources.

Experimental:

[0078] Table 1 summarizes the biobased materials that were tested as potential removal fluids 114, e.g., biobased solvents, for separating dyes 113, e.g., dispersed dyes, from solid phases 112, e.g., textile fibers. The biobased removal fluids and solids were screened according to the following experimental procedure (see FIG. 3). First, step #1), a dyed PET patch of fabric (i.e., starting solid composition 111), 50 mg in weight, was immersed (i.e., contacting 110) in about 5 ml of removal fluid 114, which, on average, corresponded to about a 1 wt % solid concentration in the mixture. However, this concentration can be varied as needed and in some embodiments of the present disclosure may vary between 0.1 wt % and 50 wt % or between 0.1 wt % and 10 wt %. The mixture was then maintained at a contacting temperature of about 100 C. for a period of time between 6 hours and 24 hours. After the contacting was complete, the now substantially dye-free PET solid patch was manually removed (i.e., first treating 120) from the now dye-containing removal fluid (i.e., effluent 122) and washed (step #2 in FIG. 3) by immersing the PET patch in 200 ml of ethanol for between 1 minute and 3 minutes to remove any residual solvent and dye from the solid PET patch. The resultant washed PET patch was then dried (step #3 in FIG. 3) in a vacuum oven at a temperature of about 100 C. for a period of time between 12 hours and 72 hours. A control, non-biobased solvent was also tested, diethylene glycol monoethyl ether (DE).

TABLE-US-00001 TABLE 1 Biobased solvents (i.e., removal fluids) tested for dye removal from PET Boiling Melting point point No. Solvent ( C.) ( C.) 1 Acetic acid (AA) 117-118 16.2 2 4-ethylguaiacol (4-EG) 234-236 15 3 4-propylguaiacol (4-PG) 264 6 4 4-propylphenol (4-PP) 232-233 21-22 5 Ethanol 78 114 6 -valerolactone (GVL) 206 31 7 Benzyl alcohol (BA) 205 16-13 8 Cyrene 227 <20 9 -caprolactone (CL) 241 2.15 10 (R)-(+)-limonene 176-177 74 11 Levulinic acid (LA) 245-246 30-33 12 Valeric acid (VA) 185 20-18 13 Ethylene glycol (EG) 197 13 14 Guaiacol (G) 205 26-29 15 Eugenol (E) 254 12 16 Isoeugenol (IE) 266 27 17 4-isopropylphenol (4-IPP) 212-213 59-61 18 Thymol 232 48-51 19 Poly(ethylene glycol) (PEG), MW = 200 NA NA 20 Poly(ethylene glycol) (PEG), MW = 400 NA NA 21 Diethylene glycol monoethyl ether (DE) 196 76

[0079] After the solvent treatment, the dye-free PET patch (i.e., recovered solid) and the extracted solution (i.e., effluent 122) included dissolved disperse dyes and potentially other additives/components were obtained. Of the starting biobased solvents (i.e., removal fluids 114) tested in this manner, four (acetic acid (A)A), 4-ethylguaiacol (4-EG), 4-propylguaiacol (4-PG), and 4-propylphenol (4-PP)) were found to be especially effective at dye removal from the starting solid compositions. It was confirmed that both thermal properties (i.e., the melting point, % crystallinity, the degradation temperature) and chemical properties (i.e., molecular weight, polydispersity) of the PET fabrics contacted had not changed significantly as a result of contact with any of the four top performing removal fluids (i.e., solvents) using the experimental procedure illustrated in FIG. 3. Further, for the four promising solvents (i.e., removal fluids 114) candidates, the colors of the dyes in the dye/removal fluid mixtures were successfully matched with the original colors of the PET fabrics, suggesting that the chemical structures of the extracted dyes were maintained, validating the feasibility of potentially recycling/reusing the recovered dyes for coloring new textile products.

[0080] Referring again to FIG. 3, the exemplary method includes a contacting step 110 (step #1), a first treating step 120 (step #2), a washing step, and a drying step. The contacting 110 provides at least three independent variables for affecting the removal of the dye from the starting solid composition: concentration of the starting solid composition in the removal fluid, temperature, and time duration of contacting. The combination of these three parameters are shown herein to affect both dye-removal efficiency and dye preservation without causing the chemical degradation of dyes. For the washing and drying steps, the conditions can be conveniently varied, e.g., to achieve temperatures above the boiling point of ethanol (78 C.). Ethanol was used as the washing step because it has a low boiling point compared to the biobased extraction solvents used for the actual dye removal. By rinsing with ethanol (a low boiling point solvent) after the dye extraction process, the fabrics dried much faster than what would have been achieved with higher boiling solvents. Nevertheless, other solvents may be used to wash the recovered solids.

[0081] FIG. 4 illustrates polyester (PET) patches tested using a method similar to that illustrated in FIGS. 1 and 3, according to some embodiments of the present disclosure. These three types of fabrics, jersey, woven, and fleece, were tested and are represented herein in abbreviated form as J, W, and F, respectively. These materials have melt temperatures in the range of 245-250 C. and crystallinity in the range of 35-45%. Each of these fabrics may be dyed various colors. The colors tested in the studies reported herein included red (R), black (B), orange (O), blue (BL), grey (GR), and green (G), each being a dispersed dye and abbreviated as indicated. FIG. 5 illustrates the chemical structures and names of biobased removal fluids (i.e., solvents) screened for the ability to treat the PET solid patches illustrated in FIG. 4, according to some embodiments of the present disclosure.

[0082] FIG. 6 illustrates photos of three PET fabrics, dyed red or black, jersey-red (JR), woven-black (WB), and fleece-black (FB), before and after solvent treatment using the procedure illustrated in FIG. 3, and using the top four performing solvent (i.e., removal fluids), acetic acid (AA), 4-ethylguaiacol (4-EG), 4-propylguaiacol (4-PG), and 4-propylphenol (4-PP). Note that these top performing solvents were identified based on testing their dye removal performance on a total of eight different samples consisting of the three fabric types (jersey, woven, and fleece) dyed 6 different colors as shown in FIGS. 7A-7D; red (R), black (B), green (G), orange (O), blue (Bl), and grey (Gr). Additionally, optical micrographs of the solvent treated fabrics were obtained to confirm almost no changes to the fabric itself upon our dye extraction process, as shown for jersey-blue (top row) and woven-black samples (bottom row) in FIG. 8) after contacting with each of AA, 4-EB, 4-PG, and 4-PP, from left to right.

[0083] Referring again to FIG. 6, the solvent-treated fabrics for woven-black and fleece-black have much lighter colors closer to pure white compared to the colors of untreated fabrics showing substantial dye extraction. However, the solvent-treated jersey-red samples retained a light pink hue, which may be attributed to stronger interactions between the red dye and the fabrics due to the dye chemistry unique to the red dye. To improve the red dye extraction performance for jersey-red fabrics, the contacting temperatures were increased from 100 C. to 150 C.) and/or the contacting times increased from 8 hours to 72 hours, which resulted in less colored fabrics after solvent treatment (see FIG. 9) without incurring substantially more weight loss to the starting solid samples (see FIGS. 10A-10C).

[0084] FIG. 11 illustrates weight loss results of the PET patches illustrated in FIGS. 4 and 6, after treatment using the procedure illustrated in FIG. 3, according to some embodiments of the present disclosure. The weight loss for AA, 4-EG, and 4-PG-treated fabrics is relatively similar. However, the weight loss for 4-PP treated fabrics is more than two-times larger than the values of the other top three removal fluids. This may be attributed to larger amounts of microfiber loss resulting from contacting with 4-PP compared to the other solvents, which may be inferred from observations of slight shrinkage of fabric, however, without apparent chemical damage to the PET (see FIG. 8 and FIGS. 12A-12C). The differences in microfiber losses may be related to each individual solvent's affinity to the solid PET, potentially with higher affinities resulting in higher fiber losses.

[0085] To further evaluate the dye extraction process, the solvent-treated PET fabrics were evaluated using CIELAB color space which quantifies the color of a material using to as L*a*b* values where L* defines black and white components, a* defines green-magenta components, and b* defines blue-yellow components (see FIGS. 13A-13C and Table 2). The lightness (L*) of the treated jersey-red (JR), woven-black (WB), and fleece-black (FB) were each lower than L* of greige sample (where a griege sample is a non-colored textile (see FIG. 13A), whereas L* of the other treated color fabrics show values much closer to the greige sample (see FIG. 14A). The red and green value (a*) is relatively low (2.9<a*<1.4) for the treated woven-black (WB) and fleece-black (FB) and other fabrics compared to the value of the treated jersey-red (JR) fabric (12<a*<21) as shown in FIG. 13B and FIG. 14B. The yellow and blue values (b*) were mostly higher than the b* greige values including jersey-red (JR), woven-black (WB), and fleece-black (FB) fabrics (see FIG. 13C and FIG. 14C), indicating that a yellow hue remains on PET solid phase after the solvent contacting step. For the color deviation from the greige sample (dE), the representative three fabrics jersey-red (JR), woven-black (WB), and fleece-black (FB) in FIG. 13D and Table 2 show relatively higher values than other fabrics (blackB, green=G, orange=O, red=red; blue=Bl, and grey=Gr) in FIG. 14D and Table 2), which suggests that the red and black dyes are less extractable than other colors, at least for the extraction conditions used in these experiments.

TABLE-US-00002 TABLE 2 Color measurements of PET fabrics (Jersey-red (JR), Jersey- blue (JBl), Jersey-green (JG), Woven-black (WB), Woven-orange (WO), Woven-green (WG), Fleece-black (FB), and Fleece-grey (FGr)) after dye extraction in bio-based solvents Sample Solvent L* a* b* dE Greige Untreated 93.74 0.8 1.26 JR AA 80.26 16.19 2.61 21.73 4-EG 82.9 12.13 0.54 16.89 4-PG 73.78 20.68 3.21 29.66 4-PP 77.78 15.97 2.11 23.17 JB1 AA 91.94 1.73 0.47 2.66 4-EG 92.39 0.21 2.19 1.74 4-PG 91.63 0.00 1.14 2.26 4-PP 93.57 0.91 2.75 1.50 JG AA 91.39 0.82 2.94 2.89 4-EG 92.28 0.62 3.81 2.94 4-PG 85.75 2.82 1.88 8.82 4-PP 91.39 0.74 2.95 2.90 WO AA 91.54 0.17 6.11 5.41 4-EG 92.31 0.19 2.76 2.16 4-PG 91.94 0.95 4.48 4.08 4-PP 92.19 0.20 4.82 4.01 WG AA 88.25 0.11 5.08 6.72 4-EG 90.45 0.42 2.63 3.58 4-PG 89.56 0.20 2.77 4.56 4-PP 87.12 1.13 4.35 7.31 WB AA 78.28 0.73 1.17 15.46 4-EG 85.22 0.39 2.44 8.61 4-PG 84.46 0.34 2.64 9.39 4-PP 78.33 1.75 0.02 15.49 FB AA 84.89 0.71 5.67 10.00 4-EG 83.30 1.37 4.62 11.18 4-PG 85.71 0.14 0.98 8.06 4-PP 80.25 0.56 2.66 13.56 FGr AA 93.01 0.15 2.84 1.86 4-EG 94.75 0.26 3.60 2.61 4-PG 93.85 0.26 3.71 2.51 4-PP 92.91 0.85 5.72 4.54

[0086] To determine dye extraction effects on PET fabrics, physicochemical properties of the PET fabrics were investigated before/after extraction by measuring molecular weights, melting temperatures, percent crystallinities, and thermal degradation temperatures. These analyses show that the molecular weight of PET fabric is almost unchanged after treatment using any of the best performing solvents (AA, 4-EG, 4-PG, and 4-PP) (see FIGS. 12A-12C and Tables 3 and 4). At higher extraction temperatures than 100 C., the molecular weight of PET fabric is reduced to ca. 90% of the untreated fabric, which indicates slight degradation of PET despite improved color removal from the fabrics (see Table 4 and FIG. 17 and FIGS. 19A-19C). The GPC traces of untreated fabrics show not only the polymer peak at 33 minutes, but also additional peaks between 40 minutes and 45 minutes, i.e., smaller molecular weight species than the polymer. Those additional peaks are attributed to other compounds present on the dyed solid phases, including the dyes themselves, as well as other textile additives since they were not observed with solid phases isolated after contacting the textiles with the removal fluids and separated as described above (e.g., filtered, washed, and dried). In other words, dyes and other additives are removed through the extraction process without chemical degradation of PET fabrics, which may prevent severe discoloration from mixing of multiple dyes as well as thermal degradation to PET and/or dye molecules in textile-to-textile recycling through mechanical recycling. It was also confirmed that thermal properties of PET fabric were not changed significantly, i.e., the melting temperature, the percent crystallinity, and the thermal degradation temperature, which indicates no thermal degradation of the fabric upon dye extraction (see FIGS. 21A-21F).

TABLE-US-00003 TABLE 3 Molecular weight of recovered PET fabrics (Jersey Red (JR), Woven Black (WB), and Fleece Black (FB)) after dye extraction in bio-based solvents Sample Solvent M.sub.w (kDa) M.sub.n (kDa) PDI JR Untreated 33.9 18.8 1.80 AA 34.3 19.7 1.74 4-EG 33.9 19.0 1.78 4-PG 33.9 18.7 1.80 4-PP 33.9 18.9 1.80 WB Untreated 34.4 18.6 1.85 AA 34.2 18.5 1.86 4-EG 34.5 18.5 1.87 4-PG 34.4 17.8 1.90 4-PP 34.0 18.6 1.83 FB Untreated 34.4 19.0 1.80 AA 34.1 18.7 1.82 4-EG 34.6 18.5 1.87 4-PG 33.6 18.6 1.80 4-PP 35.0 20.7 1.70

TABLE-US-00004 TABLE 4 GPC traces of recovered PET fabrics (Jersey Red (JR), Woven Black (WB), and Fleece Black (FB)) after dye extraction using 4-ethylguaiacol (4-EG) in different temperature. Sample Solvent M.sub.w (kDa) M.sub.n (kDa) PDI JR Untreated 32.6 19.0 1.72 100 C. 32.2 18.2 1.77 110 C. 32.6 18.7 1.74 130 C. 31.9 18.2 1.75 150 C. 29.2 17.1 1.71 WB Untreated 32.8 18.6 1.76 100 C. 34.7 19.4 1.79 110 C. 32.1 18.7 1.72 130 C. 31.4 18.2 1.73 150 C. 29.3 17.4 1.69 FB Untreated 33.1 19.2 1.73 100 C. 34.4 19.6 1.76 110 C. 34.5 19.8 1.74 130 C. 33.3 19.6 1.70 150 C. 30.9 18.6 1.66

[0087] Dye preservation and recycling: Upon dye extraction, the dyes visually maintained their original colors in solution without any significant changes as illustrated in FIGS. 15 and 16. These extracted and recovered dyes were utilized to re-dye the solid PET materials recovered using the solvent extraction process described above (see Panel B of FIG. 15) to confirm dye recyclability. Re-dyed fabrics (see Panel C of FIG. 15) clearly show that the original colors of original dyed and untreated fabrics (see Panel A of FIG. 15) were achieved in the re-dyed fabrics, although the re-dyed PET fabrics were characterized by lighter colors compared to the untreated PET fabrics. This is likely due to the dye extraction and re-dyeing processes having reduced dye contents compared to the dye contents used to originally dye the virgin PET fabrics. Additionally, the effects of different variables for dye extraction were tested, such as temperature, concentration of fabrics, and time in order to optimize the operating conditions for achieving both effective dye extraction and dye preservation. Higher contacting temperatures (up to 150 C.), lower solids concentrations (down to 1 wt %) in the removal fluid, and longer contacting times (up to 72 hours) resulted in improved color removal as illustrated in FIGS. 9, 17, and 18. The weight loss values resulting from dye removal process performed at different operating conditions confirms that higher temperatures can increase the amount of materials removed, including dyes (see FIGS. 10A-10C). However, harsher conditions, especially higher contacting temperatures and longer contacting times, can cause dye degradation as confirmed by color changes, which is not desirable for dye recycling. This degradation behavior may be attributed to the thermal stability of dye compounds in different solvents. As mentioned above, unlike dyes, the properties of the dye-extracted PET fabrics were not affected by varying contacting temperatures and/or contacting times (see FIGS. 19A-19C and FIGS. 20A-20E).

[0088] Separation of dye mixture from solvent: The commercial organic solvent nanofiltration (OSN) membranes tested exhibited good dye selectivity and solvent recovery performance, as well as excellent long-term stability in acetic acid. The BOESIG oNF-2 membrane (MWCO, 350 Da) showed the highest rejection rates (99%) of the jersey-blue dye and the fleece-black dye, and the lowest rejection rate (71%) of the woven-orange dye, while the rejection rates of the rest stayed in between (see FIG. 22A). The permeability of acetic acid remained nearly the same across all dye experiments, with slight fluctuations due to the different dye rejection rates. Because the selectivity of OSN membranes is mainly determined by size exclusion, these results provided useful information about the molecular weight of the industrial dispersive dyes: jersey-bluefleece-black>jersey-green>fleece-grey>jersey-red>woven-black>woven-orange. Despite the limited knowledge of the commercial dye compositions, these results successfully demonstrated the capability of OSN to separate and recover dyes and organic solvents (i.e., removal fluids) in the process of waste textile recycling. In a multi-stage OSN experiment (e.g., up to six total stages, with six tested here), the BOESIG oNF-2 membrane exhibited long-term chemical stability in acetic acid over 5 days (see FIG. 22B). Meanwhile, the solvent recovery rates reached more than 50% for both the highly permeable woven-black dye (50%) and the least permeable jersey-blue dye (69%) after three membrane passes. Near complete solvent recovery (90%) could also be achieved for the jersey-blue dye after 5 membrane passes and the woven-black dye after 6 membrane passes (see FIG. 22B). Separation of individual dyes from dye mixtures: The dye separation from a mixture of dyes extracted from JR, JB, JG, and WB, was conducted using counter current chromatography (CCC). To separate dyes, the solvent system for CCC was determined first. In general, a partition coefficient of products is measured in varied solvent compositions to find appropriate compositions to dissolve products partially in both upper and lower phases. For accomplishing this, a mixture of heptane, cyclopentyl methyl ether (CPME), methanol, and water, was used. Among the tested solvent compositions, the HCMWat (heptane, cyclopentyl methyl ether, methanol, and water) was used with a 3/1/3/1 volume ratio, respectively. For all samples, the operation conditions were the same: flowrate 2 mL/min, elution extrusion mode starts at 30 min, use the reverse phase (lower mobile phase). CCC systems generally use two immiscible liquid phases (i.e., nonpolar phase and polar phase) to separate compounds. In this example, heptane and CPME were used for the nonpolar phase and methanol and water were used for the polar phase.

[0089] FIG. 23A illustrates a chromatogram of the separated molecules in the red dye formulation using the HCMWat (3/1/3/1) solvent system. Each shaded area in FIGS. 23A, 23C, 23E, and 23G indicates the elution time from the CCC system for obtaining each distinctive color (1-5) shown in FIGS. 23B, 23D, 23F, and 23H. The LCMS data (see FIGS. 23B, 23D, 23F, and 23H) show distinctive molecular weight values of separated dyes. Because the lower phase was used as a mobile phase, the polar compounds eluted earlier than nonpolar ones. Five distinctive colors (yellow, green, purple, red, and pink) were separated based on different polarities, and these were analyzed by LCMS. Fraction 1 shows a strong peak that mainly indicates a red dye having 487 Da. In fraction 2, overlapped peaks in the CCC chromatogram and LCMS data suggest that there is a coelution of dyes coloring purple. Fraction 3 showed a distinctive green color with a strong MS peak at 430 Da. Fraction 4 showed a yellow color, possibly due to a coelution of a few dye mixtures based on LCMS data. Fraction 5 also was red in tint (pink) with a similar MS peak to Fraction 1, indicating that the dye in Fraction 5 has a similar molecular structure to the one in Fraction 1 but has more nonpolar functional groups.

[0090] Other extracted dye mixtures were (blue, green, and black) were also separated using CCC with the same solvent system, demonstrating that CCC can be applied to various types of dye mixtures (see FIGS. 23C-23H). Multiple dyes were successfully separated from each dye mixture showing various colors in effluents, exhibiting that multiple dyes were used to generate the textile color. Each dye effluent was collected and analyzed by LCMS. Based on MS data, most dyes have a molecular size between 330 and 600 Da, suggesting a possibility of nanofiltration to concentrate dyes and recover extracting solvent.

[0091] FIG. 24 illustrates a flow-through extraction system for extracting dyes from fabrics, according to some embodiments of the present disclosure. One biobased solvent was tested, acetic acid as a proof of concept. The exemplary flow-through system included the following features: pure glacial acetic acid, the bioderived removal fluid (i.e., solvent) was sourced from a reservoir, and, using a pump, transferred through a heated transfer line to a flow-through bed packed with the fabric. After the extraction was completed, the resultant mixture of the solvent and the dye was directed to a knock-out pot for condensing and cooling the solvent/dye mixture with a sampling port, and resultant dye-containing mixture was collected. The reaction conditions are as follows: Pressure: 100 psig, Flow rate: 1 ml/min. (Additional flow-through bed details: bed height=42 cm; bed diameter=15.89 mm (inner); typical mass of dyed fabric positioned in the bed=: 4-5 g; typical total volume of acetic acid passed through the bed=300-400 ml)

[0092] FIGS. 25A-25C illustrate temperatures of the solvent as measured at the inlet, outlet, and longitudinal center along the length of the bed versus online time. Three temperature control schemes were tested: (FIG. 25A) a one-step process with a target temperature of 100 C., (FIG. 25B) a two-step process with target temperatures of 100 C. and 150 C., and (FIG. 25C) a two-step process with target temperatures of 100 C. and 180 C. A reason for using the two-step processes was to achieve better dye-removal performance, as a remaining pink hue was observed on the treated fabric using the one-step process targeting 100 C.

[0093] FIGS. 26-29 illustrate the results obtained from the flow-through system for both the dyes and fabrics. FIG. 26 illustrates photographs of the dyed fabrics before and after treatment, along with the extracted solutions. The percentage values indicate the weight loss after the solvent treatments. Note that #4 is a duplicate of #2. The extracted solution was collected every 30 minutes from the sampling port, and the reaction temperature is indicated for each solution.

[0094] FIG. 27 illustrates GPC data that measure the dyes' molecular weight before and after solvent treatments. The primary peak between 22-26 minutes corresponds to PET, while the smaller peak between 28-32 minutes corresponds to the dyes. The molecular weight (MW) values from the GPC data are presented in Table 5 below. These data show that the MW of the PET decreased as the reaction temperature increased, indicating degradation of the PET.

[0095] FIG. 28 illustrates DSC data corresponding to thermal properties, including melting temperature and % crystallinity, of PET fabrics before and after solvent treatment. Change in the melting temperature is not significant, however decrease in % crystallinity at higher temperature than 100 C. is noticeable.

[0096] FIG. 29 illustrates TGA data provides insights into the thermal degradation behavior of PET fabrics, and it shows no significant differences among the different samples.

[0097] Table 5 tabulates the molecular weight of recovered PET fabrics (Jersey Red (JR)) after dye extraction via the flow-through reactor in acetic acid (AA). The molecular weight of recovered PET fabrics is correlated to the intrinsic viscosity (IV) of them by the Mark-Houwink equation, and the IV values determine the application type of recovered PET.

TABLE-US-00005 TABLE 5 PET properties before and after dye extraction via the flow-through reactor in acetic acid (AA). Sample Solvent M.sub.w (kDa) M.sub.n (kDa) PDI JR Untreated 36.1 19.7 1.84 100 C. 32.5 17.4 1.87 150 C. 31.2 16.6 1.88 180 C. 24.2 14.2 1.70

Materials and Methods:

[0098] Fabrics and Solvents: Colored PET fabrics (jersey-red (JR), jersey-blue (JB), jersey-green (JG), woven-black (WB), woven-orange (WO), woven-green (WG), fleece-black (FB), and fleece-grey (FG)) and greige PET fabric are provided by Patagonia. All the organic solvents are purchased through either Sigma Aldrich or TCI Chemicals.

[0099] Dye Extraction: PET fabrics were cut into 2 cm.sup.2 (50 mg) per sample and submerged in a solvent (5 ml) to make 1-5 wt. % solution in a glass vial (contacting step). The fabric solution was heated in the heating block on the hot plate at the given temperature (between 80 C. and 150 C.) for a specified amount of time (between 0.5 hours and 72 hours). After the solvent treatment, the treated fabric was transferred to ethanol at RT to remove any solvent remaining on the fabric, followed by drying in a vacuum oven overnight (between 6 hours and 12 hours) at a temperature between 100 C. and 130 C. For a larger than 50 mg pieces of fabric, a round bottom flask was used as a vessel for contacting the fabric with the removal fluid and a reflux condenser was utilized as needed.

[0100] High Temperature Size Exclusion Chromatography (HT-SEC): HT-SEC analysis of the polymer samples was performed using a Tosoh EcoSec HLC-8321 High Temperature SEC System with autosampler and a differential refractive index (DRI) detector. The mobile phase used was o-Chlorophenol (OCB) (Sigma Aldrich-HPLC Grade) which was used as-received with no inhibitor added. Polymer separation was performed using four (4) Tosoh TSKgel columns in the following order: TSKgel guard column (HHR (30) HT2 7.5 mm I.D.7.5 cm., PN 22891), TSKgel GMHHR (20) HT2 (7.8 mm I.D.30 cm columns, PN 22888), and two sequential TSKgel G2000 columns (HHR (20) HT2 7.8 mm I.D.30 cm columns, PN 22890). Additionally, a reference column, specifically a TSKgel GMH HR-H (S) HT2 (7.8 mm I.D.30 cm column, PN 22889) was used. Tosoh's Polystyrene-Quick Kit-M (PN 21916) was used to create the calibration curve from a series of polystyrene (PS) Mw standards. The calibration curve was verified using Tosoh PS F-10 (Mw=106,000 Daltons (Da)P/N 05210)), PSS Polymer (Mw=66,000 DaBatch No: ps14057), Wyatt (Mw=30,000 DaP/N P8402-03001), and PSS Polymer (Mw=1,200 DaBatch No: ps14057). The solvent stock was set to 40 C. while the pump oven was set to 50 C. The columns, RI detector, injector valve, and autosampler were all set to 110 C. Samples were prepared in Tosoh 10 ml high temperature sample vials with PTFE caps. 6-20 mg of sample were placed in a Tosoh high temperature 26 m stainless steel mesh filter and OCB solvent was added to reach an end concentration of 1.7 mg/mL and heated on the autosampler for two (2) hours with occasional agitation. Samples were injected into a 300 L sample loop and ran at an operating flow rate of 0.8 mL/min for the sample columns. Meanwhile, the reference column was set to an operating flow rate of 0.4 mL/min. Run time for all standards and samples was about 80 minutes. Eco-Sec 8321 software (Tosoh) was used for data processing. Mark-Houwink correction values were applied to the polystyrene calibration curve. Mark-Houwink values used for polystyrene were K=12.110-5 dL/g and Alpha=0.707. Mark-Houwink values used for polyester materials were K=96.310-5 dL/g and Alpha=0.658.

[0101] Analysis of Dyes: Samples were analyzed on an Agilent 1100 LC system (Agilent Technologies, Santa Clara, CA) equipped with a diode array detector (DAD) and a G6120A single quadrupole mass spectrometer. Each sample was injected at a volume of 5 L on a Phenomenex Kinetex 1.7 um EVO C18 100 column (Phenomenex, Torrance, CA, 2.1100 mm, Part #OOD-4726-AN)). The column temperature was maintained at 30 C. and the buffers used were 0.1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B). A gradient program was used to separate the analytes of interest: (A)=80% and (B)=20% at time t=0; (A)=60% and (B)=40% at t=5 min; (A)=40% and (B)=60% at t=10 min; (A)=20% and (B)=80% at t=15 min; (A)=5% and (B)=95% at t=20 min; hold (A)=5% and (B)=95% at t=23 min; (A)=80% and (B)=20% at t=23.01 min; hold (A)=80% and (B)=20% at t=29 min. The flow rate was held constant at 0.40 mL min.sup.1 resulting in a run time of 29 minutes. The mass spectrometer was scanned in both positive and negative mode from 100-1500 m/z with a gas temperature of 350 C., drying gas flow at 12.0 L/min, nebulizer pressure of 40 psig, and a VCap of 3500 v in both positive and negative mode electrospray. The diode array detector (DAD) scanned from 245 nm to 900 nm UV-VIS ranges and plotted 254 nm, 280 nm, and 360 nm wavelengths. The total ion chromatogram (TIC) and DAD data was utilized to compare and tentatively identify candidates, by molecular weight and wavelength, of dyes detected in samples. Compounds that had strong signals in the visible range (380-700 nm) were assumed to be dyes, and [M+H] m/z were recorded.

[0102] Membrane-based dye separation via organic solvent nanofiltration (OSN): Dye rejection rates and solvent recovery were evaluated in a dead-end filtration cell (Sterlitech HP4750, US). The cell has an effective membrane area of 14.6 cm.sup.2. The OSN performance was characterized using a commercial organic nanofiltration membrane (BORSIG oNF-2, Sterlitech, US) with the as-extracted dye-acetic acid solutions (3-7 wt. %) as the feed at room temperature at 500 psi of applied pressure generated from inert nitrogen gas. The volume of the feed was 300 ml. A suspended stir bar was added to maintain the homogeneity of the solution inside the filtration cell. All membranes were pre-compacted by pure acetic acid at 500 psi to ensure steady performance. Dye concentrations of permeate and feed were determined by a Total Organic Carbon (TOC) analyzer. Membrane permeance was calculated as follows:

[00001]$P=\frac{w}{AtP}$

where w is the weight of permeate collected during the time period t, A is the membrane area, P is the applied transmembrane pressure for the filtration experiment. The rejection was calculated using the following equation:

[00002]$R=\left(1-\frac{C_p}{C_f}\right)100\%$

where C.sub.p and C.sub.f represent the dye concentration of the permeate and the feed solution. Their concentrations were determined by a TOC analyzer.

[0103] A multi-stage membrane experiment to evaluate the solvent recovery performance was performed. The starting volume of the feed was 300 ml. In each stage, we applied a constant external pressure of 500 psi to achieve a complete passage of solvent. The permeate from the previous stage was used as the feed for the next state. The dye concentrations of the permeate at different stages were determined by a TOC analyzer.

[0104] Counter Current Chromatography (CCC)-based dye separation: CCC (S1000, Dynamic Extractions, UK) has a rotor where a column consists of a length of perfluoroalkoxy tubing (i.d. 4 mm bore) coiled on two bobbins. The column volume was 81 mL. A chiller was attached to CCC to maintain the constant temperature in a CCC chamber at 25 C. The inlet and outlet of the column were connected to an HPLC system via flying leads tubing. An HPLC pump (Waters 515) and VICI 6-/4-ways switching valves were connected to the column inlet and the column outlet was connected to a diode array detector (ECOM, TOY18DAD), and fraction collector (ECF2098) in series. The HPLC system was controlled by Clarity software (v. 8.1).

[0105] The extracted dyes mixtures from JB, JR, JG, and WB were separated using CCC. The solvent system for CCC was prepared by mixing heptane, cyclopentyl methyl ether (CPME), methanol, and water (HCMWat) with the 3/1/3/1 volume ratio where the total volume was 800 mL. When the HCMWat solvent system reached equilibrium after mixing, the upper and lower phases were taken separately using a separate funnel and then used for CCC stationary and mobile phases, respectively. For all dye mixtures, the feed samples were prepared by dissolving the dried extracted dyes in the HCMWat solution (50/50% UP and LP) and were loaded on the sample loop (4.5 mL) using a 6-way switching valve. For all samples, the operation conditions were the same: flowrate 2 mL/min, elution extrusion mode starts at 30 min, use the reverse phase (lower mobile phase). The effluent fractions were collected every 2 mL and analyzed with LC-MS. CCC tests were completed at temperatures between 23 C. and 25, pressures at about 200 psi, and rotor speeds of about 1400 RPM.

Examples

[0106] Example 1. A method comprising: a first contacting of a starting solid composition comprising a starting solid phase and a dye with a removal fluid resulting in a first mixture comprising the starting solid phase, the dye, and the removal fluid, wherein the removal fluid comprises at least one of a cyclic compound, a glycol, an alcohol, or an acid.

[0107] Example 2. The method of Example 1, wherein the removal fluid is biobased.

[0108] Example 3. The method of Examples 1 or 2, further comprising a first treating of the first mixture resulting in a recovered solid phase comprising the starting solid phase and an effluent comprising the dye.

[0109] Example 4. The method of any one of Examples 1-3, further comprising a second treating of the effluent resulting in the separating and recovery of the dye and the removal fluid.

[0110] Example 5. The method of any one of Examples 1-4, further comprising a second contacting of the recovered solid phase with an alcohol, resulting in a second recovered solid phase that has a concentration of the dye that is lower than a concentration of the dye for the recovered solid phase.

[0111] Example 6. The method of any one of Examples 1-5, wherein the removal fluid is bioderived as determined by ASTM-D6866.

[0112] Example 7. The method of any one of Examples 1-6, wherein the removal fluid is characterized by at least one physical property or performance metric.

[0113] Example 8. The method of any one of Examples 1-7, wherein the physical property or performance metric comprises at least one of a water solubility between, a flash point, a melting point, a boiling point, or a toxicity value.

[0114] Example 9. The method of any one of Examples 1-8, wherein the removal fluid has a water solubility between substantially immiscible with water and substantially completely soluble in water.

[0115] Example 10. The method of any one of Examples 1-9, wherein the removal fluid has a water solubility between 1 gram removal fluid per liter of water (g/L) and 603 g/L.

[0116] Example 11. The method of any one of Examples 1-10, wherein the removal fluid has a flash point between 10 C. and 230 C., or between 40 C. and 113 C.

[0117] Example 12. The method of any one of Examples 1-11, wherein the removal fluid has a boiling point between 65 C. and 290 C., or between 117 C. and 236 C.

[0118] Example 13. The method of anyone of Examples 1-12, wherein the removal fluid has a LD50 oral toxicity between 348 mg/kg and 22,000 mg/kg, or between 348 mg/kg and 3,310 mg/kg.

[0119] Example 14. The method of anyone of Examples 1-13, wherein the removal fluid has a LD50 dermal toxicity between 660 mg/kg and 6400 mg/kg, or between 1100 mg/kg and 3310 mg/kg.

[0120] Example 15. The method of any one of Examples 1-14, wherein the removal fluid has a melting point between 150 C. and 63 C., or between 6 C. and 22 C.

[0121] Example 16. The method of any one of Examples 1-15, wherein the acid comprises at least one of acetic acid, levulinic acid, or n-valeric acid.

[0122] Example 17. The method of any one of Examples 1-16, wherein the glycol comprises at least one of ethylene glycol or polyethylene glycol, propylene glycol, or polypropylene glycol.

[0123] Example 18. The method of any one of Examples 1-17, wherein the cyclic compound comprises at least one of guaiacol, a guaiacol derivative, a phenol compound, cyrene, -valerolactone, -caprolactone, benzyl alcohol, or limonene.

[0124] Example 19. The method of any one of Examples 1-18, wherein the guaiacol derivative comprises at least one of 4-ethylguaiacol, 4-propylguaiacol, eugenol, or isoeugenol.

[0125] Example 20. The method of any one of Examples 1-19, wherein the phenol compound comprises at least one of phenol, 4-propyl phenol, thymol, 4-isopropylphenol, or 2-isopropylphenol.

[0126] Example 21. The method of any one of Examples 1-20, wherein the alcohol comprises at least one of ethanol, isopropyl alcohol, n-butanol, 4-methyl-2-pentanol, or methanol.

[0127] Example 22. The method of any one of Examples 1-21, wherein the starting solid phase comprises at least one of a synthetic material or a naturally occurring material.

[0128] Example 23. The method of any one of Examples 1-22, wherein the synthetic material comprises at least one of a polymer, a resin, or an oligomer.

[0129] Example 24. The method of any one of Examples 1-23, wherein the starting solid phase is characterized by at least one of a physical property or a performance metric.

[0130] Example 25. The method of any one of Examples 1-24, wherein the physical property or performance metric comprises at least one of a melting point, a percent crystallinity, a degradation temperature, a molecular weight, or polydispersity.

[0131] Example 26. The method of any one of Examples 1-25, wherein the melting point is between 230 C. and 270 C., or between 245 C. and 253 C.

[0132] Example 27. The method of any one of Examples 1-26, wherein the percent crystallinity is between 20% and 60%, or between 35% and 42%, Example 28. The method of any one of Examples 1-27, wherein the degradation temperature, corresponding to about 5 wt % loss, is between 350 C. and 450 C., or between 400 C. and 410 C.

[0133] Example 29. The method of any one of Examples 1-28, wherein the molecular weight (M.sub.n(number average)) is between 15,000 Da and 26,000 Da, or between 18,000 Da and 21,000 Da.

[0134] Example 30. The method of any one of Examples 1-29, wherein the molecular weight (M.sub.w(weight average)) is between 30,000 Da and 40,000 Da, or between 34,000 Da and 35,000 Da.

[0135] Example 31. The method of any one of Examples 1-30, wherein the polydispersity (PDI) is between 1.4 and 2.3, or between 1.7 and 1.9.

[0136] Example 32. The method of any one of Examples 1-31, wherein the polymer comprises at least one of polyester, polyamide, polyurethane, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polychlorotrifluoroethylene, polyethylene terephthalate, polychloroprene, polyacrylonitrile, polytetrafluoroethylene, polyimide, or polybutylene adipate terephthalate.

[0137] Example 33. The method of any one of Examples 1-32, wherein the oligomer comprises at least one of polyester, polyamide, polyurethane, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polychlorotrifluoroethylene, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polychloroprene, polyacrylonitrile, polytetrafluoroethylene, polyimide, or polybutylene adipate terephthalate.

[0138] Example 34. The method of any one of Examples 1-33, wherein the naturally occurring material comprises at least one of lignin, cellulose, or hemicellulose.

[0139] Example 35. The method of any one of Examples 1-34, wherein the naturally occurring material comprises at least one of a plant-based material or an animal-based material.

[0140] Example 36. The method of any one of Examples 1-35, wherein the plant-based material is derived from at least one of cotton, hemp, coir, linen, ramie, sisal, jute, kapoc, or ramina.

[0141] Example 37. The method of any one of Examples 1-36, wherein the animal-based material is derived from at least one of alpaca, Angora rabbit, Angora goat, Kashmir goat, sheep, camel, or silkworm.

[0142] Example 38. The method of any one of Examples 1-37, wherein the starting solid phase is in a form comprising at least one of a fabric, fiber, pellet, powder, flake, granule, or film.

[0143] Example 39. The method of any one of Examples 1-38, wherein the starting fiber has a diameter between 1.0 D and 2.2 D (Denier), or between 1.2 D and 2.0 D (Denier).

[0144] Example 40. The method of any one of Examples 1-39, wherein the dye comprises at least one of a colorant, a pigment, a dyestuff, a stain, or a tincture.

[0145] Example 41. The method of any one of Examples 1-40, wherein the dye comprises at least one of a natural dye or a synthetic dye.

[0146] Example 42. The method of any one of Examples 1-41, wherein the natural dye is ionic.

[0147] Example 43. The method of any one of Examples 1-42, wherein the synthetic dye comprises at least one of an acid dye, a basic dye, an ionic dye, a direct dye, an azo dye, an anthraquinone dye, an indigo dye, a phthalocyanine dye, a nitro dye, a nitroso dye, a disperse dye, a vat dye, a mordant dye, a reactive dye, a solvent dye, or a sulfur dye.

[0148] Example 44. The method of any one of Examples 1-43, wherein the starting solid composition further comprises an additive comprising at least one of a fixative, a mordant, a UV-absorbent, a water repellent, an anti-odor additive, an antioxidant, an optical brightener, or a processing aid.

[0149] Example 45. The method of any one of Examples 1-44, wherein the first contacting is performed in a stirred tank reactor or a flow-through bed.

[0150] Example 46. The method of any one of Examples 1-45, wherein the stirred tank reactor or flow-through bed is a continuous reactor.

[0151] Example 47. The method of any one of Examples 1-46, wherein the continuous reactor has two or more stages.

[0152] Example 48. The method of any one of Examples 1-47, wherein the stirred tank reactor utilizes at least one of a mixer, an agitator, or ultrasound.

[0153] Example 49. The method of any one of Examples 1-48, wherein the mixer or agitator is operated at between 200 rpm and 500 rpm.

[0154] Example 50. The method of any one of Examples 1-49, wherein the starting solid composition is positioned within the flow-through bed and the removal fluid is passed through the flow-through bed.

[0155] Example 51. The method of any one of Examples 1-50, wherein the amount of removal fluid passed through the flow-through bed and the amount of starting solid composition positioned within the flow-through bed are at a mass ratio between 1 g of starting solid composition to 1 g of removal fluid (1:1) and 1:1000, or between 1:10 and 1:100.

[0156] Example 52. The method of any one of Examples 1-51, wherein the flow-through bed is operated at a temperature between 100 C. and 180 C.

[0157] Example 53. The method of any one of Examples 1-52, wherein the flow-through bed is operated at a first temperature between 90 C. and 110 C. for a first period of time and a second temperature between 150 C. and 180 C. for a second period of time.

[0158] Example 54. The method of any one of Examples 1-53, wherein the first period of time is between 10 minutes and 250 minutes.

[0159] Example 55. The method of any one of Examples 1-54, wherein the second period of time is between 10 minutes and 100 minutes.

[0160] Example 56. The method of any one of Examples 1-55, wherein the first contacting is performed at a temperature above the glass transition temperature of the starting solid phase.

[0161] Example 57. The method of any one of Examples 1-56, wherein the temperature is between 90 C. and 200 C., or between 90 C. and 150 C.

[0162] Example 58. The method of any one of Examples 1-57, wherein the first contacting is performed for a period of time between 10 minutes and 12 hours.

[0163] Example 59. The method of any one of Examples 1-58, wherein the second contacting comprises rinsing the recovered solid phase with the alcohol at room temperature for less than five minutes.

[0164] Example 60. The method of any one of Examples 1-59, wherein the second contacting further comprises separating the second recovered solid phase from the alcohol.

[0165] Example 61. The method of any one of Examples 1-60, wherein the second contacting further comprises drying the second recovered solid phase.

[0166] Example 62. The method of any one of Examples 1-61, wherein the drying is performed at a temperature of at least 100 C.

[0167] Example 63. The method of any one of Examples 1-62, wherein the drying is performed at a pressure below atmospheric pressure.

[0168] Example 64. The method of any one of Examples 1-63, wherein the drying is performed for a period of time between one hour and three days.

[0169] Example 65. The method of any one of Examples 1-64, wherein the first treating is performed using at least one of a filtration unit or a gravitational unit.

[0170] Example 66. The method of any one of Examples 1-65, wherein the first treating removes microfibers formed during the first contacting.

[0171] Example 67. The method of any one of Examples 1-66, wherein the filtration unit comprises at least one of a membrane filter or a rotating ceramic filter.

[0172] Example 68. The method of any one of Examples 1-67, wherein the membrane filter comprises at least one of polyamide, polypropylene (PP), polyethersulfone (PES), or polytetrafluoroethylene (PTFE).

[0173] Example 69. The method of any one of Examples 1-68, wherein the membrane filter comprises a plurality of pores having an average pore size of less than or equal to 0.2 m.

[0174] Example 70. The method of any one of Examples 1-69, wherein the gravitational method comprises at least one of a settling tank or a centrifuge.

[0175] Example 71. The method of any one of Examples 1-70, wherein the second treating comprises at least one of absorption, adsorption, evaporation, distillation, physical separation, crystallization, precipitation, or chromatography.

[0176] Example 72. The method of any one of Examples 1-71, wherein the chromatography includes at least one of flash column chromatography, counter-current chromatography (CCC), or ion chromatography.

[0177] Example 73. The method of any one of Examples 1-72, wherein the CCC uses a mixture of heptane, cyclopentyl methyl ether, methanol, and water to separate the dye from the removal fluid.

[0178] Example 74. The method of any one of Examples 1-73, wherein the heptane and the cyclopentyl methyl ether are present at a mass ratio of heptane to cyclopentyl methyl ether between 10:1 and 1:1 or about 3:1.

[0179] Example 75. The method of any one of Examples 1-74, wherein the cyclopentyl methyl ether and the methanol are present at a mass ratio of cyclopentyl methyl ether to methanol between 1:10 and 10:1 or about 1:3.

[0180] Example 76. The method of any one of Examples 1-75, wherein the methanol and the water are present at a mass ratio of methanol to water between 10:1 and 1:1 or about 3:1.

[0181] Example 77. The method of any one of Examples 1-76, wherein the CCC is performed at a temperature between 22 C. and 40 C., or between 22 C. and 30 C.

[0182] Example 78. The method of any one of Examples 1-77, wherein the CCC is performed at an inlet pressure between 100 psig and 500 psig, or between 180 psig and 220 psig. Example 79. The method of any one of Examples 1-78, wherein the CCC is performed at a rotor speed between 1000 RPM and 2000 RPM, or between 1200 RPM and 1600 RPM.

[0183] Example 80. The method of any one of Examples 1-79, further comprising recycling the removal fluid to the first contacting.

[0184] Example 81. The method of any one of Examples 1-80, further comprising directing the dye to a process for colorizing a solid with the dye.

[0185] The foregoing discussion and examples have been presented for purposes of illustration and description. The foregoing is not intended to limit the aspects, embodiments, or configurations to the form or forms disclosed herein. In the foregoing Detailed Description for example, various features of the aspects, embodiments, or configurations are grouped together in one or more embodiments, configurations, or aspects for the purpose of streamlining the disclosure. The features of the aspects, embodiments, or configurations, may be combined in alternate aspects, embodiments, or configurations other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention that the aspects, embodiments, or configurations require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment, configuration, or aspect. While certain aspects of conventional technology have been discussed to facilitate disclosure of some embodiments of the present invention, the Applicants in no way disclaim these technical aspects, and it is contemplated that the claimed invention may encompass one or more of the conventional technical aspects discussed herein. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate aspect, embodiment, or configuration.