AMINE-BASED SOLVENTS FOR TEMPERATURE SWING SOLVENT EXTRACTION

Abstract

Disclosed are systems and methods for desalinating high-salinity brines via temperature swing solvent extraction (TSSE) using an amine-based solvent.

Claims

1. A method for desalinating high-salinity brines, the method comprising: contacting a feed brine with an amine-based solvent under conditions effective for temperature swing solvent extraction (TSSE) to produce a substantially desalinated product, wherein the amine-based solvent comprises sec-butyl-isopropyl-amine and/or a glycerol-based amine solvent.

2. The method of claim 1, wherein the glycerol-based amine solvent is represented by Formula I, or a salt thereof: ##STR00072## wherein each R.sup.1, R.sup.2, and R.sup.3 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic alkyl, a substituted or unsubstituted linear, branch, or cyclic alkoxy, a substituted or unsubstituted linear, branch, or cyclic alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, and R.sup.3 is not hydrogen.

3. The method of claim 2, wherein each R.sup.1, R.sup.2, and R.sup.3 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkoxy, a substituted or unsubstituted linear, branch, or cyclic Cl.sub.1- C.sub.6 alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, and R.sup.3 is not hydrogen.

4. The method of claim 2, wherein each R.sup.1, R.sup.2, and R.sup.3 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxy, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, and R.sup.3 is not hydrogen.

5. The method of claim 2, wherein R.sup.1 and R.sup.2 are the same.

6. The method of claim 2, wherein R.sup.1 and R.sup.2 are different.

7. The method of claim 1, wherein the glycerol-based amine solvent is represented by Formula II, or a salt thereof: ##STR00073## wherein each R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic alkyl, a substituted or unsubstituted linear, branch, or cyclic alkoxy, a substituted or unsubstituted linear, branch, or cyclic alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is not hydrogen.

8. The method of claim 7, wherein each R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkoxy, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is not hydrogen.

9. The method of claim 7, wherein each R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxy, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is not hydrogen.

10. The method of claim 7, wherein R.sup.1, R.sup.2, R.sup.4, and R.sup.5 are the same.

11. The method of claim 1, wherein the amine-based solvent comprises more than one amine-based solvent.

12. The method of claim 1, wherein the conditions effective for TSSE comprise: contacting the feed brine with the amine-based solvent at a first temperature to form an extractant phase comprising water from the feed brine dissolved in the solvent and a raffinate; separating the extractant phase and the raffinate; heating or cooling the extractant phase to second temperature to thereby adjust the miscibility of the water in the amine-based solved to form the substantially desalinated water product and a solvent phase; and separating the substantially desalinated water product from the solvent phase.

13. The method of claim 12, further comprising recycling the separated solvent phase for additional TSSE processes.

14. The method of claim 1, wherein the feed brine has a total dissolved solids of 50,000 ppm or more.

15. A system for desalinating high-salinity brines, the system comprising: an extraction unit configured to receive a feed brine and an amine-based solvent and contact the feed brine and amine-based solvent under conditions effective for temperature swing solvent extraction (TSSE) to produce a substantially desalinated product, wherein the amine-based solvent comprises sec-butyl-isopropyl-amine and/or a glycerol-based amine solvent.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0032] The accompanying figures, which are incorporated in and constitute a part of this specification, illustrate several aspects described below.

[0033] FIG. 1 shows an example system for desalinating a high-salinity brine according to an exemplary aspect.

[0034] FIG. 2A shows initial configurations of (panel a) bulk DIPA-water mixture and (panel b) DIPA-water interfacial system.

[0035] FIG. 2B shows the average solvent properties within each cluster: (panel a) density, (panel b) solvation free energy of water

[00001] $(_{w}^{}),$

(panel c) number of HBs per solvent molecule, and (panel d) nitrogen site partial charge. The properties are obtained by averaging among the solvents within each cluster, and the error bars are calculated assuming a confidence level of 0.95.

[0036] FIG. 3 shows the radial distribution function between the hydrogen site (H) bonded the carbon atom of DIPA and oxygen site (Ow) of the water molecule for different fixed point charge models and a polarizable one (AMOEBA).

[0037] FIG. 4 shows cluster members of (panel a) C1, (panel b) C2, (panel c) C3, and (panel d) C4 obtained using the k-means method and pure solvent as well as solvent-water properties as inputted features. Molecule labels are presented in Table 7.

[0038] FIG. 5 shows energy consumption versus total dissolved solids concentration for various desalination technologies.

[0039] FIG. 6 shows a general illustration of the working principles of temperature swing solvent extraction (TSSE).

[0040] FIG. 7 shows glycerol derived from natural sources and associated activated forms (top). Transformation to green chemical platforms (bottom) for brine desalination.

[0041] FIG. 8 shows electron density of glycerol mapped from the SCF density.

[0042] FIG. 9 shows automated identification of key interaction sites on prototype solvent molecules (left); automated classification of the solvent-solvent and solvent-water interactions (% contribution to overall interaction energy) among dozens of prototype solvent candidates (blue=electrostatic, red=dispersion, grey=repulsion) (right).

[0043] FIG. 10 shows a general overview of simulation screening and experimental workflow.

[0044] FIG. 11 shows PMF calculations used to evaluate transport barriers from the brine phase to the solvent phase.

DETAILED DESCRIPTION

[0045] The materials, compounds, compositions, articles, and methods described herein may be understood more readily by reference to the following detailed description of specific aspects of the disclosed subject matter and the Examples and Figures included therein.

[0046] Before the present materials, compounds, compositions, and methods are disclosed and described, it is to be understood that the aspects described below are not limited to specific synthetic methods or specific reagents, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0047] Also, throughout this specification, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which the disclosed matter pertains. The references disclosed are also individually and specifically incorporated by reference herein for the material contained in them that is discussed in the sentence in which the reference is relied upon.

General Definitions

[0048] In this specification and in the claims that follow, reference will be made to a number of terms, which shall be defined to have the following meanings: Throughout the description and claims of this specification the word comprise and other forms of the word, such as comprising and comprises, means including but not limited to, and is not intended to exclude, for example, other additives, components, integers, or steps.

[0049] As used in the description and the appended claims, the singular forms a, an, and the include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a composition includes mixtures of two or more such compositions, reference to the compound includes mixtures of two or more such compounds, reference to an agent includes mixture of two or more such agents, and the like.

[0050] Optional or optionally means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0051] Phase, as used herein, generally refers to a region of material having a substantially uniform composition which is a distinct and physically separate portion of a heterogeneous system. The term phase does not imply that the material making up a phase is a chemically pure substance, but merely that physical properties of the material making up the phase are essentially uniform throughout the material, and that these physical properties differ significantly from the physical properties of another phase within the material. Examples of physical properties include density, index of refraction, and chemical composition.

[0052] It is understood that throughout this specification the identifiers first and second are used solely to aid in distinguishing the various components and steps of the disclosed subject matter. The identifiers first and second are not intended to imply any particular order, amount, preference, or importance to the components or steps modified by these terms.

Chemical Definitions

[0053] As used herein, the term substituted is contemplated to include all permissible substituents of organic compounds. In a broad aspect, the permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, and aromatic and nonaromatic substituents of organic compounds. Illustrative substituents include, for example, those described below. The permissible substituents can be one or more and the same or different for appropriate organic compounds. For purposes of this disclosure, the heteroatoms, such as nitrogen, can have hydrogen substituents and/or any permissible substituents of organic compounds described herein which satisfy the valences of the heteroatoms. This disclosure is not intended to be limited in any manner by the permissible substituents of organic compounds. Also, the terms substitution or substituted with include the implicit proviso that such substitution is in accordance with permitted valence of the substituted atom and the substituent, and that the substitution results in a stable compound, e.g., a compound that does not spontaneously undergo transformation such as by rearrangement, cyclization, elimination, etc.

[0054] Z.sup.1, Z.sup.2, Z.sup.3, and Z.sup.4 are used herein as generic symbols to represent various specific substituents. These symbols can be any substituent, not limited to those disclosed herein, and when they are defined to be certain substituents in one instance, they can, in another instance, be defined as some other substituents.

[0055] The term aliphatic as used herein refers to a non-aromatic hydrocarbon group and includes branched and unbranched, alkyl, alkenyl, or alkynyl groups.

[0056] The term alkyl as used herein is a branched or unbranched saturated hydrocarbon group of 1 to 24 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, eicosyl, tetracosyl, and the like. The alkyl group can also be substituted or unsubstituted. The alkyl group can be substituted with one or more groups including, but not limited to, alkyl, halogenated alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol, as described below.

[0057] Throughout the specification alkyl is generally used to refer to both unsubstituted alkyl groups and substituted alkyl groups; however, substituted alkyl groups are also specifically referred to herein by identifying the specific substituent(s) on the alkyl group. For example, the term halogenated alkyl specifically refers to an alkyl group that is substituted with one or more halides, e.g., fluorine, chlorine, bromine, or iodine. The term alkoxyalkyl specifically refers to an alkyl group that is substituted with one or more alkoxy groups, as described below. The term alkylamino specifically refers to an alkyl group that is substituted with one or more amino groups, as described below, and the like. When alkyl is used in one instance and a specific term such as alkylalcohol is used in another, it is not meant to imply that the term alkyl does not also refer to specific terms such as alkylalcohol and the like.

[0058] This practice is also used for other groups described herein. That is, while a term such as cycloalkyl refers to both unsubstituted and substituted cycloalkyl moieties, the substituted moieties can, in addition, be specifically identified herein; for example, a particular substituted cycloalkyl can be referred to as, e.g., an alkylcycloalkyl. Similarly, a substituted alkoxy can be specifically referred to as, e.g., a halogenated alkoxy, a particular substituted alkenyl can be, e.g., an alkenylalcohol, and the like. Again, the practice of using a general term, such as cycloalkyl, and a specific term, such as alkylcycloalkyl, is not meant to imply that the general term does not also include the specific term.

[0059] The term alkoxy as used herein is an alkyl group bound through a single, terminal ether linkage; that is, an alkoxy group can be defined as OZ.sup.1 where Z.sup.1 is alkyl as defined above.

[0060] The term alkenyl as used herein is a hydrocarbon group of from 2 to 24 carbon atoms with a structural formula containing at least one carbon-carbon double bond. Asymmetric structures such as (Z.sup.1Z.sup.2)CC(Z.sup.3Z.sup.4) are intended to include both the E and Z isomers. This can be presumed in structural formulae herein wherein an asymmetric alkene is present, or it can be explicitly indicated by the bond symbol CC. The alkenyl group can be substituted with one or more groups including, but not limited to, alkyl, halogenated alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol, as described below.

[0061] The term alkynyl as used herein is a hydrocarbon group of 2 to 24 carbon atoms with a structural formula containing at least one carbon-carbon triple bond. The alkynyl group can be substituted with one or more groups including, but not limited to, alkyl, halogenated alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol, as described below.

[0062] The term aryl as used herein is a group that contains any carbon-based aromatic group including, but not limited to, benzene, naphthalene, phenyl, biphenyl, phenoxybenzene, and the like. The term heteroaryl is defined as a group that contains an aromatic group that has at least one heteroatom incorporated within the ring of the aromatic group. Examples of heteroatoms include, but are not limited to, nitrogen, oxygen, sulfur, and phosphorus. The term non-heteroaryl, which is included in the term aryl, defines a group that contains an aromatic group that does not contain a heteroatom. The aryl or heteroaryl group can be substituted or unsubstituted. The aryl or heteroaryl group can be substituted with one or more groups including, but not limited to, alkyl, halogenated alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol as described herein. The term biaryl is a specific type of aryl group and is included in the definition of aryl. Biaryl refers to two aryl groups that are bound together via a fused ring structure, as in naphthalene, or are attached via one or more carbon-carbon bonds, as in biphenyl.

[0063] The term cycloalkyl as used herein is a non-aromatic carbon-based ring composed of at least three carbon atoms. Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc. The term heterocycloalkyl is a cycloalkyl group as defined above where at least one of the carbon atoms of the ring is substituted with a heteroatom such as, but not limited to, nitrogen, oxygen, sulfur, or phosphorus. The cycloalkyl group and heterocycloalkyl group can be substituted or unsubstituted. The cycloalkyl group and heterocycloalkyl group can be substituted with one or more groups including, but not limited to, alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol as described herein.

[0064] The term cycloalkenyl as used herein is a non-aromatic carbon-based ring composed of at least three carbon atoms and containing at least one double bound, i.e., CC. Examples of cycloalkenyl groups include, but are not limited to, cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, cyclohexadienyl, and the like. The term heterocycloalkenyl is a type of cycloalkenyl group as defined above, and is included within the meaning of the term cycloalkenyl, where at least one of the carbon atoms of the ring is substituted with a heteroatom such as, but not limited to, nitrogen, oxygen, sulfur, or phosphorus. The cycloalkenyl group and heterocycloalkenyl group can be substituted or unsubstituted. The cycloalkenyl group and heterocycloalkenyl group can be substituted with one or more groups including, but not limited to, alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, nitro, silyl, sulfo-oxo, sulfonyl, sulfone, sulfoxide, or thiol as described herein.

[0065] The term cyclic group is used herein to refer to either aryl groups, non-aryl groups (i.e., cycloalkyl, heterocycloalkyl, cycloalkenyl, and heterocycloalkenyl groups), or both. Cyclic groups have one or more ring systems that can be substituted or unsubstituted. A cyclic group can contain one or more aryl groups, one or more non-aryl groups, or one or more aryl groups and one or more non-aryl groups.

[0066] The term aldehyde as used herein is represented by the formula C(O)H. Throughout this specification C(O) or CO is a shorthand notation for CO, which is also referred to herein as a carbonyl.

[0067] The terms amine or amino as used herein are represented by the formula NZ.sup.1Z.sup.2, where Z.sup.1 and Z.sup.2 can each be substitution group as described herein, such as hydrogen, an alkyl, halogenated alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above. Amido is

##STR00004##

[0068] The term carboxylic acid as used herein is represented by the formula C(O)OH. A carboxylate or carboxyl group as used herein is represented by the formula

##STR00005##

[0069] The term carbamide means compounds represented by the form N(Z.sup.1)(CO)N(Z.sup.1).sub.2 where each Z.sup.1 can be, independently, an alkyl, alkenyl, alkynyl, aryl, arylalkyl, cycloalkyl, carbonyl, ether, haloalkyl, heteroaryl and heterocyclyl.

[0070] The term carbamate means compounds represented by the form Z.sup.1OC(O)N(Z.sup.1), Z.sup.1OC(O)N(Z.sup.1) Z.sup.1, or OC(O)N(Z.sup.1).sub.2, where each Z.sup.1 can be, independently, an alkoxy, aryloxy, alkyl, alkenyl, alkynyl, aryl, arylalkyl, cycloalkyl, ether, formyl, haloalkyl, heteroaryl, and heterocyclyl. Carbamates include, e.g., arylcarbamates and heteroaryl carbamates.

[0071] The term ester as used herein is represented by the formula OC(O)Z.sup.1 or [0072] C(O)OZ.sup.1, where Z.sup.1 can be an alkyl, halogenated alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

[0073] The term ether as used herein is represented by the formula Z.sup.1OZ.sup.2, where Z.sup.1 and Z.sup.2 can be, independently, an alkyl, halogenated alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

[0074] The term ketone as used herein is represented by the formula Z.sup.1C(O)Z.sup.2, where Z.sup.1 and Z.sup.2 can be, independently, an alkyl, halogenated alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

[0075] The term halide or halogen as used herein refers to the fluorine, chlorine, bromine, and iodine.

[0076] The term hydroxyl as used herein is represented by the formula OH.

[0077] The term nitro as used herein is represented by the formula NO.sub.2.

[0078] The term silyl as used herein is represented by the formula SiZ.sup.1Z.sup.2Z.sup.3, where Z.sup.1, Z.sup.2, and Z.sup.3 can be, independently, hydrogen, alkyl, halogenated alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

[0079] The term sulfonyl is used herein to refer to the sulfo-oxo group represented by the formula S(O).sub.2Z.sup.1, where Z.sup.1 can be hydrogen, an alkyl, halogenated alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

[0080] The term sulfonylamino or sulfonamide as used herein is represented by the formula S(O).sub.2NH.

[0081] The term thiol as used herein is represented by the formula SH.

[0082] The term thio as used herein is represented by the formula S.

[0083] Unless stated to the contrary, a formula with chemical bonds shown only as solid lines and not as wedges or dashed lines contemplates each possible isomer, e.g., each enantiomer, diastereomer, and meso compound, and a mixture of isomers, such as a racemic or scalemic mixture.

[0084] Reference will now be made in detail to specific aspects of the disclosed materials, compounds, compositions, articles, and methods, examples of which are illustrated in the accompanying Examples and Figures.

Methods and Systems for Desalinating High-Salinity Brines

[0085] Disclosed herein are methods for desalinating high-salinity brines. In some aspects, the method includes contacting a feed brine with an amine-based solvent under conditions effective for temperature swing solvent extraction (TSSE) to produce a substantially desalinated product, wherein the amine-based solvent comprises sec-butyl-isopropyl-amine and/or a glycerol-based amine solvent.

[0086] In some aspects, the amine-based solvent comprises sec-butyl-isopropyl-amine (CAS 33546-49-5) represented by:

##STR00006##

or a salt thereof. The solvent can comprise a single enantiomer of sec-butyl-isopropyl-amine, i.e., either the S or the R, enantiomer, or a racemic mixture of S and R, or a scalemic mixture of S and R enantiomers.

[0087] In some aspects, the amine-based solvent includes a glycerol-based amine solvent. The glycerol-based amine solvent may be a glycerol derivative. As used herein, a glycerol derivative refers to a compound that is derived from or includes a significant portion of glycerol as a backbone or core structural component (e.g., substituted with an amine group).

[0088] Glycerol, 1,2,3-trihydroxypropane, is a simple polyol comprising a propane with three alcohol functional groups. Glycerol has a wide range of applications, including use as an organic solvent and as a sweetener in foods. Glycerol is a byproduct of biodiesel production, and due to the recent expansion of biodiesel product, there is a glut of glycerol.

[0089] In some aspects, the glycerol-based amine solvent is represented by Formula I, or a salt thereof:

##STR00007## [0090] wherein each R.sup.1, R.sup.2, and R.sup.3 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic alkyl, a substituted or unsubstituted linear, branch, or cyclic alkoxy, a substituted or unsubstituted linear, branch, or cyclic alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, and R.sup.3 is not hydrogen.

[0091] In some aspects according to Formula I, each R.sup.1, R.sup.2, and R.sup.3 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkoxy, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, and R.sup.3 is not hydrogen.

[0092] In some aspects according to Formula I, each R.sup.1, R.sup.2, and R.sup.3 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxy, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, and R.sup.3 is not hydrogen.

[0093] In some aspects, according to Formula I, each of R.sup.1, R.sup.2, and R.sup.3 are the same. In some aspects according to Formula I, R.sup.1 and R.sup.2 are the same. In some aspects according to Formula I, at least one of R.sup.1, R.sup.2, and R.sup.3 is different. In some aspects according to Formula I, R.sup.1, R.sup.2, and R.sup.3 are all different. In some aspects, none of R.sup.1, R.sup.2, and R.sup.3 are hydrogen.

[0094] In some aspects, the glycerol-based amine solvent is represented by Formula II, or a salt thereof:

##STR00008## [0095] wherein each R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic alkyl, a substituted or unsubstituted linear, branch, or cyclic alkoxy, a substituted or unsubstituted linear, branch, or cyclic alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is not hydrogen.

[0096] In some aspects according to Formula II, each R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkoxy, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is not hydrogen.

[0097] In some aspects according to Formula II, each R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxy, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is not hydrogen.

[0098] In some aspects, R.sup.1, R.sup.2, R.sup.4, and R.sup.5 are the same. In some aspects, at least one of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is different. In some aspects, at least two of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 are different. In some aspects, each of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is different. In some aspects, the amine-based solvent comprises a substantially symmetrical compound. In some aspects, none of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 are hydrogen.

[0099] In some aspects, according to any of Formulas I-II, the amine-based solvent comprises a substantially symmetric compound. In some aspects, the amine-based solvent comprises more than one amine-based solvent.

[0100] In some aspects, the conditions effective for TSSE includes: [0101] contacting the feed brine with the amine-based solvent at a first temperature to form an extractant phase comprising water from the feed brine dissolved in the solvent and a raffinate; [0102] separating the extractant phase and the raffinate (e.g., via gravity separation); heating or cooling the extractant phase to second temperature to thereby adjust the miscibility of the water in the amine-based solved to form the substantially desalinated water product and a solvent phase; and [0103] separating the substantially desalinated water product from the solvent phase. In some aspects, the first temperature is higher than the second temperature. In some aspects, the first temperature is lower than the second temperature. In some aspects, the method further includes recycling the separated solvent phase for additional TSSE processes.

[0104] In some aspects, the feed brine has a total dissolved solids of 50,000 ppm or more (e.g., 75,000 ppm or more, 100,000 ppm or more, 150,000 ppm or more, 200,000 ppm or more, or 250,000 ppm or more).

[0105] In various aspects, disclosed herein are systems configured to perform any one of the methods described herein. For example, FIG. 1 illustrates an example system 100 for desalinating high-salinity brines using temperature swing solvent extraction (TSSE) according to one aspect.

[0106] In the system 100, a feed brine 104 and an amine-based solvent 102 are contacted in an extraction vessel 110 (e.g., a liquid-liquid extraction column) to form an extractant phase 114 including a portion of water from the feed brine 104 dissolved in the amine-based solvent 102 and a raffinate 112. In various aspects, the amine-based solvent includes sec-butyl-isopropyl-amine and/or a glycerol-based amine solvent. In some aspects, the amine-based solvent is sec-butyl-isopropyl-amine. In some aspects, the amine-based solvent is glycerol-based amine solvent.

[0107] In some aspects, it is advantageous to heat and/or cool the feed brine 104 and/or amine-based solvent 102 prior to or during the extraction. For example, the feed brine 104 and/or amine-based solvent 102 can be adjusted to a first temperature to optimize the amount of water from the feed brine 104 dissolved in the amine-based solvent 102 during extraction. Determination of the first temperature typically depends on a number of factors, including, for example, the concentration of salts in the feed brine, the molecular characteristics of the amine-based solvent (e.g., polarity, size), and physical conditions (e.g., external pressure). In this regard, the optimal first temperature may be explored experimentally or can be estimated using molecular simulations.

[0108] In some aspects, the glycerol-based amine solvent is represented by Formula I, or a salt thereof:

##STR00009## [0109] wherein each R.sup.1, R.sup.2, and R.sup.3 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic alkyl, a substituted or unsubstituted linear, branch, or cyclic alkoxy, a substituted or unsubstituted linear, branch, or cyclic alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, and R.sup.3 is not hydrogen.

[0110] In some aspects according to Formula I, each R.sup.1, R.sup.2, and R.sup.3 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkoxy, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, and R.sup.3 is not hydrogen.

[0111] In some aspects according to Formula I, each R.sup.1, R.sup.2, and R.sup.3 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxy, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, and R.sup.3 is not hydrogen.

[0112] In some aspects, according to Formula I, each of R.sup.1, R.sup.2, and R.sup.3 are the same. In some aspects according to Formula I, R.sup.1 and R.sup.2 are the same. In some aspects according to Formula I, at least one of R.sup.1, R.sup.2, and R.sup.3 is different. In some aspects according to Formula I, R.sup.1, R.sup.2, and R.sup.3 are all different. In some aspects, none of R.sup.1, R.sup.2, and R.sup.3 are hydrogen.

[0113] In some aspects, the glycerol-based amine solvent is represented by Formula II, or a salt thereof:

##STR00010## [0114] wherein each R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic alkyl, a substituted or unsubstituted linear, branch, or cyclic alkoxy, a substituted or unsubstituted linear, branch, or cyclic alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is not hydrogen.

[0115] In some aspects according to Formula II, each R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkoxy, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is not hydrogen.

[0116] In some aspects according to Formula II, each R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is independently hydrogen, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkyl, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxy, a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.3 alkoxyalkyl, or a substituted or unsubstituted linear, branch, or cyclic C.sub.1-C.sub.6 alkenyl; with the proviso that at least one of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is not hydrogen.

[0117] In some aspects, R.sup.1, R.sup.2, R.sup.4, and R.sup.5 are the same. In some aspects, at least one of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is different. In some aspects, at least two of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 are different.

[0118] In some aspects, each of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 is different. In some aspects, the amine-based solvent comprises a substantially symmetrical compound. In some aspects, none of R.sup.1, R.sup.2, R.sup.4, and R.sup.5 are hydrogen.

[0119] In some aspects, according to any of Formulas I-II, the amine-based solvent comprises a substantially symmetric compound. In some aspects, the amine-based solvent comprises more than one amine-based solvent.

[0120] Since some of the water in the feed brine 104 is dissolved in the amine-based solvent 102, the raffinate 112 includes a higher concentration of salts compared to the feed brine 104. The concentrated raffinate 112 may be subjected to additional (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10) separation processes (e.g., further liquid-liquid extractions using amine-based solvents) or disposed. However, in some aspects, The additional separation processes may be arranged to maximize recovery of product water from the feed brine 104 without incurring substantial energy costs.

[0121] Following the separation of the extractant phase 114 and the raffinate 112, the extractant phase 114 is subjected to a temperature swing operation via heat exchanger 140. The temperature swing operation involves adjusting the temperature of the extractant 114 from a first temperature to a second temperature thereby affecting the miscibility of dissolved water in the amine-based solvent. In some aspects, the temperature swing is achieved by raising the temperature of the extractant 114. In some aspects, the temperature swing is achieved by lowering the temperature of the extractant 114. The temperature adjusted mixture 116 is then subjected to a separation vessel 120 (e.g., a liquid-liquid extraction column) to provide biphasic mixture including a solvent phase 124 and a desalinated water product 122. The solvent phase 124 and the desalinated water product 122 may be separated using any known technique, such as gravity separation. Although the heat exchanger 140 and separation vessel 120 are shown as separate elements in FIG. 1, it is also envisioned that the temperature swing operation via the heat exchanger 140 can occur within the separation vessel 120.

[0122] The desalinated water product 122 includes substantially purified water. As used herein, the term substantially purified water refers water that includes 80 wt. % or more of water, e.g., 82 wt. % or more, 84 wt. % or more, 86 wt. % or more, 88 wt. % or more, 90 wt. % or more, 92 wt. % or more, 94 wt. % or more, 95 wt. % or more, 96 wt. % or more, 97 wt. % or more, 98 wt. % or more, 99 wt. % or more, 99.5 wt. % or more, or 99.9 wt. % or more. In some aspects, an amount of total dissolved solids (TDS) in the feed brine is reduced by 80% or more compared to the desalinated product, e.g., 82% or more, 84% or more, 86% or more, 88% or more, 90% or more, 92% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, 99% or more, 99.5% or more, or 99.9% or more. In some aspects, the system is configured to recover 30% or more of the water in the feed brine, e.g., 35% or more, 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, 96% or more, 97% or more, 98% or more, 99% or more, 99.5% or more, or 99.9% or more. In some aspects, the desalinated product is subject to further processing (e.g., reverse osmosis). In some aspects, the desalinated product is recovered without any further processing or separation steps.

[0123] System 100 shown in FIG. 1 further includes a solvent phase recovery 130 in which the solvent phase 124 is recycled and returned for use in the desalination of feed brines. The solvent recovery 130 can include various conditioning processes to ensure the proper conditions for desalination are met. For example, the solvent phase recovery 130 includes a heat exchanger 150 which adjust the temperature of the solvent if needed before mixing with the feed brine 104 in the separation vessel 110. Although heat exchangers 140 and 150 are shown as separate elements in FIG. 1, in some aspects, the various streams may be thermally coupled such that heat from one location is used to drive a temperature increase at another location in the system.

EXAMPLES

[0124] To further illustrate the principles of the present disclosure, the following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compositions, articles, and methods claimed herein are made and evaluated. They are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their disclosure. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperatures, etc.); however, some errors and deviations should be accounted for. Unless indicated otherwise, temperature is C. or is at ambient temperature, and pressure is at or near atmospheric. There are numerous variations and combinations of process conditions that can be used to optimize product quality and performance. Only reasonable and routine experimentation will be required to optimize such process conditions.

Example 1: Characterization of Amine-Based Solvents

[0125] Introduction. Over the last few years, alternative methods to thermal and reverse osmosis techniques have been proposed..sup.1-4 Notably, temperature swing solvent extraction (TSSE) has proven effective for treating high-salinity brines. Temperature swing solvent extraction (TSSE) (also known as solvent extraction desalination) is a desalination technique that uses of an organic solvent whose miscibility with water is strongly dependent on temperature and can avoid the thermodynamic constraints of evaporative processes (FIGS. 5 and 6). Properly selecting a low-polarity water-selective organic solvent is the main issue in this approach. However, due to the several factors involved (solubility of salt in solvent phase, solvent toxicity, etc.), selecting an optimum solvent formulation can be challenging. Several different solvent classes have been evaluated for TSSE, including long-chain fatty acids,.sup.5-7 imidazolium-based ionic liquids (ILs),.sup.8 and amines.sup.77. Short-chain secondary (2) amine, such as diisopropylamine (DIPA, C.sub.6H.sub.15N), have demonstrated some of the best performance to date..sup.9-14

[0126] Although some effort has been made to understand the TSSE performance of different amine-based solvents, the specific molecular features of solvent candidates are still an open issue. To investigate this issue, this study used molecular simulation techniques to better understand the molecular features and thermodynamic properties of water uptake in amine-based solvents. Initially, nearly 60 amine-based solvents were selected, restricted to molecular compositions containing from four to six carbons. The list of solvents, their chemical structures, and labels are shown in Table 7. For purposes of this study, these specific solvents were chosen as they represent 6-carbon analogues of the DIPA (M0) molecule in order to explore the influence of different molecular characteristics, such as branching, aliphaticity, and nitrogen location in the solvent structure.

[0127] Molecular Simulation Methodology. The MD simulations were carried out using the Gromacs package version 2021.1 (Lindahl, 2021), and the initial molecular configurations were built using the Packmol package. (Martinez, 2009). Based on the initial coordinates, the energy was minimized using the steepest decedent method. Then, the Parrinello-Rahman (Nos6, 1983; Parrinello, 1981) and v-rescaling method (Bussi, 2007) were used to simulate an isobaric-isothermic (NPT) ensemble, with time constants of 5 ps and 1 ps, respectively; the equations of motion were integrated using the leap-frog algorithm with a timestep of 2 fs.

[0128] The OPLS-AA force field bonded and non-bonded parameters were derived using the LigParGen web server. (Jorgensen, 2005; Dodda, 2017). Consistent with the OPLS-AA parameterization, partial atomic charges were calculated using the CHELPG method, (Breneman, 1990) based on the optimized molecular structures obtained via density functional theory (DFT) calculations performed at the B3LYP/6-31+(d,p) level of theory. All DFT calculations were carried out using Gaussian09. (Frisch, 2009). The semi-empirical 1.14*CM1A-LBCC charge method, (Jorgensen, 2005) known for its compatibility with OPLS-AA, was also tested to evaluate the influence of the charge method. As for water models, the SPC/E water model was used due to its good performance in predicting pure water properties (Vega, 2011) and its compatibility with the OPLS-AA force field. AmberTools 22 was used to obtain GAFF bonded and non-bonded parameters, (Case, 2005) besides, AmberTools was also used to obtain AM1-BCC charges. (Jakalian, 2000; Jakalian, 2002). Consistent with the OPLS-AA and GAFF parametrizations, a cutoff distance of 1 nm was used for the Lennard-Jones (LJ) and coulombic interactions. The AMOEBA force field parameterization of DIPA was done using the Poltype 2 package. (Walker, 2022).

[0129] To calculate the thermodynamic properties of pure solvents, simulation boxes with 400 solvent molecules were run for a total of 40 ns (30 ns of equilibration followed by a production stage of 10 ns). Explicitly, based on these simulations, the density, volumetric thermal expansion coefficient, solvent-solvent binding free energy, and heat of vaporization were calculated. The volumetric thermal expansion coefficient (ap) was calculated by

[00002] $\begin{matrix} _{p} = \frac{1}{V} {(\frac{V}{T})}_{p}, & (1) \end{matrix}$ [0130] where T is the temperature, V is the volume of the system is, and the differential was evaluated numerically by simulating the solvent at 294, 298, and 303 K. The heat of vaporization (H.sup.vap) was calculated based on the pure liquid solvent internal potential energy (U.sub.l) using

[00003] $\begin{matrix} H^{v a p} = U_{g} - U_{l} + R T, & (2) \end{matrix}$ [0131] where R is the ideal gas constant and U.sub.g is the internal potential energy of the gas phase, obtained by performing a simulation of an isolated molecule. To estimate the solvent-solvent binding free energy (w) the study used

[00004] $\begin{matrix} w (r) = RT \ln (g (r)) & (3) \end{matrix}$ [0132] where g(r) is the solvent-solvent radial distribution function (RDF).

[0133] The molecular interactions between solvent and water were explored through molecular dynamics simulations of mixtures comprising 400 solvent molecules and 400 water molecules, maintaining a 1:1 molar ratio. Similarly to the pure solvent systems, the bulk water-solvent mixtures were simulated for a total of 40 ns (30 ns of equilibration followed by 10 ns of production). Herein, gmx hbonds tools was used to calculate the average number of hydrogen-bonded (HB); in molecular dynamics framework, an HB is defined as hydrogen-donor-acceptor pair within a cutoff radius of 0.35 nm at an angle of 35 degrees. The solvent-water binding energy was also estimated using Eq. 3.

[0134] The solvation free energy of water in the amine-based solvents

[00005] $(_{w}^{})$

was calculated by incrementally coupling the water molecule in the final configuration of the bulk pure solvent simulations; similarly, the same approach was used to calculate the solvent in water solvation free energy

[00006] $(_{s o l v}^{}) .$

To do this, the coupling parameters for van der Waals and coulombic interactions were .sup.vdw/coul={0.0, 0.2, 0.4, 0.6, 0.8, 1.0}, and the multistate Bennett acceptance ratio estimator (MBAR), available in Alchemical Analysis package, (Klimovich, 2015), was used to estimate the solvation free energy. (Shirts, 2008; Shirts, 2003; Bennett, 1976).

[0135] Following the recommendations of Klimovich et al., 1 ns of equilibration followed by 5 ns of production was enough to obtain accurate estimates.

[0136] The properties described above were used in the clustering step, based on the k-means clustering method, (Kubat, 2021; Rebala, 2019), in which all features were standardized using a z-score

[00007] $\begin{matrix} z_{i j} = \frac{x_{i j} - {\overset{}{x}}_{j}}{_{x_{j}}}, & (4) \end{matrix}$

where {tilde over (x)}.sub.j and .sub.x.sub.j are the average and standard deviation of the jth thermodynamic property, and x.sub.ij is the jth thermodynamic property of the ith solvent.

[0137] Finally, in the interfacial simulations, the systems were equilibrated for 300 ns, followed by 100 ns for production purposes. The water-solvent interfacial systems were used to calculate the average density profiles across the simulation box from which the composition of the solvent-rich and aqueous phases were directly calculated. (Barbosa, 2022)

[0138] It is worth highlighting that classical molecular dynamics (MD) is a purely predictive modeling approach, which does not typically require experimental data fitting, and it only requires moderate computational resources. Nonetheless, it is advantageous to rigorously benchmark the accuracy of these molecular models against established experimental results or more sophisticated modeling methods for validation. In this approach, the study compared classical force fields, often referred to as fixed point charge models, and polarizable force fields, such as the widely recognized AMOEBA (Atomic Multipole Optimized Energetics for Biomolecular Applications)..sup.15 It is worth highlighting that despite the superior capability of polarizable force fields (e.g., AMOEBA) in accurately predicting thermodynamic and structural properties,.sup.16-17 their significant computational demands present a practical limitation. This is particularly pertinent when screening many solvents, as the heightened computational costs of polarizable force fields often outweigh their enhanced precision, guiding us toward a more balanced approach in selecting suitable modeling techniques for extensive solvent analysis. FIG. 3 shows the radial distribution function (g(r)) between the hydrogen site bonded to nitrogen (H) and the oxygen site of water (Ow), obtained by simulating an MD box with 2,000 water molecules and 30 M0 molecules (FIG. 2A, panel a). The OPLS-AA force field.sup.18-20 using 1.14*CM1A-LBCC atomic partial charges.sup.19 and General Amber Force Field (GAFF).sup.21 using the atomic partial charges obtained using the AM1-BCC method.sup.22,23 presented a better agreement with the g(r) predicted by the AMOEBA force field, which suggests a good performance of these force fields to describe the structure of DIPA in water.

[0139] The study further investigated the performance of OPLS-AA and GAFF (two of the most common intermolecular force fields) by benchmarking the predicted liquid-liquid phase equilibrium for M0 and dipropylamine (M1) against the data obtained experimentally by Davison..sup.24 To do this, interfacial system simulation boxes were built (FIG. 2A, panel b), in which the composition of each phase, solvent-rich and aqueous phases, are directly obtained. Table 1 shows the obtained results by using OPLS-AA (1.14*CM1A-LBCC). As observed, this force field prediction is in close agreement with the experimental data in this temperature range. This suggests that this modeling approach can reasonably predict the liquid-liquid phase equilibrium for amine-based solvents. Although GAFF performs well when predicting structural properties, as discussed before, the interfacial simulation suggested no water solubility. For this reason, OPLS-AA (1.14*CM1A-LBCC) was determined to be the ideal force field for these systems, and it was used to gather all of the simulation production data reported here.

TABLE-US-00001 TABLE 1 Predicted and experimental liquid-liquid equilibria for M0 and M1 using OPLS-AA (1.14*CM1A-LBCC). Experimental values obtained by Davison are presented in parentheses. Temp. Solvent Molar fraction Solvent (K) Water-rich phase Solvent-rich phase DIPA 303 0.009 (0.021) 0.276 (0.215) 313 0.005 (0.013) 0.435 (0.408) DPA 303 0.006 (0.007) 0.495 (0.425) 313 0.005 (0.005) 0.574 (0.498)

[0140] As highlighted above, M0 is often considered one of the best current solvents for TSSE desalination. To provide a more rigorous evaluation of these features, the k-means clustering method was used. This unsupervised learning (clustering) method aims to partition N observations into K clusters, mainly based on an optimization step of the so-called inertia criteria..sup.25,26 The approach for screening a large number of amine-based solvents in the clustering stage prioritizes the use of thermodynamic properties which require low computational cost to obtain. Based on the results obtained by using the k-means method, the solvents affiliated with the M0 cluster were further evaluated for TSSE desalination performance by simulating their properties in an interfacial model.

[0141] As mentioned, the experiment started by predicting pure solvent properties, such as density, volumetric thermal expansion coefficient, solvent-solvent binding free energy, the heat of vaporization, number of H-bonded (N.sub.HB) sites, and the solvation free energy of water in the amine solvents

[00008] $(_{w}^{}) .$

The pure fluid thermodynamic properties and thermodynamic and structural properties of water-solvent mixtures are summarized in Table 8 and Table 9, respectively; the clustering analysis results based on the thermodynamic properties of Table 8 and 9 are presented in FIG. 4.

[0142] The clustering analysis yields four clusters with distinct molecular topologies: (a) cluster C1 (M50 geometric center) is made up of all primary (1) amines; (b) cluster C2 (M19 geometric center) is composed of 2 and tertiary (30) amines with shorter alkyl chains, including M0; (c) cluster C3 (M13 geometric center) is purely comprised of cyclic unsaturated amines; and (d) cluster C4 (M8 geometric center) mainly consists of unsaturated cyclic solvents. FIG. 2B shows the average solvent properties of each cluster: density,

[00009] $_{w}^{},$

N.sub.HB, and the nitrogen site partial charge. As shown, the densities of C1 and C4 are similar, while C2 and C3 correspond to the lowest and the highest average densities, respectively. Concerning the water solvation behavior in C1, C2, C3, and C4, FIG. 2B, panel b indicates that water solvation is most favorable in the C1 cluster (1 amines). At the same time,

[00010] $_{w}^{}$

predicts similar solvation behavior in C2, C3, and C4, in which there is a slightly more favorable solvation of water in C4 solvents. Interestingly, the average number of HBs agrees with the overall behavior predicted by

[00011] $_{w}^{};$

a more significant number of HB sites is found in C1 solvents, followed by C4, while similar behavior is observed for C2 and C3. Although not included as input in the k-means method clustering, the average number of H-bonds and the partial charge on the nitrogen sites are slightly correlated. For instance, the solvents with more electronegative nitrogen sites are assigned to C1, while those with less electronegative sites are found in the C3 cluster, and a smaller difference is observed between C2 and C4.

[0143] Now, based on the clustering analysis performed above, the study proceeded to analyze the amine solvent water uptake. In this analysis, solvent molecules were targeted that are grouped within the M0 cluster (C2) since M0 has already been identified as a promising candidate for the TSSE process, as mentioned before. Consistent with the MD prediction benchmark presented in Table 1, the interfacial simulations were carried out at 303 and 313 K; additional simulations were performed at 343 K for promising solvents, consistent with the typical water recovery temperature range for the TSSE process.

[0144] Table 2 presents the predicted liquid-liquid equilibrium for the amine-based solvents of C2. In this approach, a global mass fraction of z.sub.solv=0.3 was used in order to optimize the computational cost of the interfacial systems' MD simulation. Considering the short-chain 2 amine of C2 (FIG. 4), the MD simulations predicted fully miscible behavior in the evaluated temperature range and global composition, which suggests that these solvents are not good candidates for TSSE application, and these results are not shown in Table 2. In the evaluated set, M11 and M19 presented the largest water uptake, followed by M0, M10, M9, M2, M1, and M18. Beyond water uptake at room temperature, another relevant solvent feature for TSSE is composition temperature sensitivity. As observed, M0 presented a more pronounced X.sub.313/X.sub.303 and X.sub.343/X.sub.303, in which X.sub.i=X.sub.iX.sub.303 and X.sub.i is the solvent mole fraction at 303, 313, or 343 K. Notably, the high solubility sensitivity with temperature is in strong agreement with the good performance of M0 in the TSSE process previously reported on literature, as highlighted above. However, Table 2 also suggests a good performance of some of the six-carbon amine-based solvents, such as M11, M19, M10, M9, and M1, as it is possible to observe by looking at X.sub.313/X.sub.303 and X.sub.343/X.sub.303; meanwhile, M2 and M18 were predicted not to perform well.

[0145] Finally, it was stated before that shorter-chain 2 amine solvents of C2, such as M44 and M46, are predicted to be completely miscible in water. Without wishing to be bound by theory, it was hypothesized that mixing these solvents could partially improve the performance of a six-carbon amine-based solvents such as M0. To explore this possibility, interfacial system simulations were run using the same global composition (z.sub.solv=0.3, z.sub.w=0.7) and a mixture molar solvent fractions of x.sub.solv,M0=0.8 and x.sub.solv,M44/M46=0.2. Table 2 shows the predicted phase behavior for the mixture M0+M44 and M0+M46. By mixing these shorter-chain solvents with M0, a slightly higher water uptake is predicted in the solvent-rich phase for both mixtures. Considering the temperature sensitivity of solubility, a better performance is predicted for the mixture M0+M46 compared with M0 and the mixture M0+M44. These MD predictions suggest that the mixture of M0 with a shorter-chain amine-based could lead to a better TSSE performance.

TABLE-US-00002 TABLE 2 Predicted liquid-liquid equilibrium of different amine solvents. Herein, X.sub.i = X.sub.i X.sub.303, in which X.sub.i is the solvent molar fraction at 303, 313, or 343 K. All calculations were performed at 1 bar. Solvent Molar fraction Temp. Water-rich Solvent-rich X.sub.313/X.sub.303 X.sub.343/X.sub.303 Solvent (K) phase phase (%) (%) M0 303 0.009 0.276 50.104 176.051 313 0.005 0.414 343 0.003 0.761 M1 303 0.007 0.495 15.972 44.416 313 0.005 0.574 343 0.002 0.715 M2 303 0.004 0.440 8.237 313 0.005 0.476 M9 303 0.001 0.381 18.242 80.484 313 0.002 0.451 343 0.001 0.688 M10 303 0.008 0.364 15.674 85.472 313 0.006 0.421 343 0.003 0.676 M11 303 0.012 0.236 25.178 150.512 313 0.008 0.295 343 0.005 0.591 M18 303 0.006 0.506 12.888 313 0.004 0.571 M19 303 0.008 0.235 31.201 130.571 313 0.007 0.308 343 0.004 0.541 M44 + 303 0.0103 0.2245 29.570 168.720 M0 313 0.0076 0.2908 343 0.0037 0.6032 M46 + 303 0.009 0.238 41.393 188.808 M0 313 0.007 0.337 343 0.004 0.689

[0146] Experimental screening of C6-solvents. The following solvents were tested experimentally to understand the effect of the nitrogen location on 6-carbon amine solvents: DIPA, dipropylamine (DPA), ethylbutylamine (EPA), methylpentylamine (MPA), hexylamine (HA), cyclohexylamine (CHA), and aniline. All of these solvents have a reported pKa (pulled from PubChem) of 10.6-11.07, except for aniline, which has a pKa of 4.6. Each solvent was mixed with DI water or brine at room temperature, allowed to extract for 1 hour and phase separated. Then, the solvent phase was put in a water bath at 70 C. for 1 h and the resulting phases were separated. Aniline showed no measurable performance in any of the tests performed, and therefore is not used in any of the experiments described below.

[0147] First, the study tested the solvents with DI water (i.e., no salt) to investigate the water uptake and release properties of each solvent. Additionally, the study tested for the temperature change upon mixing. Table 3 shows the results of the DI water mixing results. The water mass recovered was calculated using equation 5 where m.sub.wr is the mass of water recovered, m.sub.wi is the initial mass of water added to the solvent, and m.sub.w70 is the mass of water recovered after releasing from the solvent at 70 C.

[00012] $\begin{matrix} m_{w r} = \frac{m_{w 70}}{m_{w i}} 1 0 0 & (5) \end{matrix}$

TABLE-US-00003 TABLE 3 Water mass recovered (%) and temperature change of mixing ( C.) of the solvents with DI water using a 1:1 volume ratio of solvent:water. n 3 unless otherwise noted. Water Mass Mixing Solvent Recovered (%) T ( C.) HA 36.6 0.8 8.3 0.1 MPA 40.7 (n = 1) 8.8 (n = 1) EBA 21.5 (n = 1) 7.6 (n = 1) DPA 14.0 0.2 6.8 0.7 DIPA 40.5 1.8 8.1 0.5 CHA 0.0 0.0 10.1 0.3 Aniline 0.0 0.0 0.9 0.5

[0148] Next, the study investigated the effect of change in volume upon mixing the solvent and either DI water or a 100,000 ppm NaCl brine. 4 mL of solvent was added to 4 mL of the aqueous phase at room temperature (20-22 C.). If these mixtures behave ideally, the volumes would be additive to 8 mL. Since the solvent/organic phase will take in water, the volume of the mixture will be reduced. Table 4 presents the volume of mixing results with DI water, and Table 5 presents the results with the NaCl brine. The DI water results do not show much difference as the solvents all perform similarly, except for HA and CHA, which are both miscible with the aqueous phase. The NaCl brine testing demonstrates that HA and CHA are not suitable solvents since HA forms a gel and CHA forms a one phase mixture. MPA had the most different results with a lower aqueous volume and larger organic volume than the other solvents. EPA, DPA, and DIPA were all relatively similar with some small differences.

TABLE-US-00004 TABLE 4 Volume of mixing results with 4 mL of solvent and 4 mL of DI water. n 3. Mixing Aqueous Organic Solvent Volume (mL) Volume (mL) Volume (mL) HA 7.69 0.09 N/A (one phase) N/A (one phase) MPA 7.65 0.06 1.36 0.05 6.29 0.03 EBA 7.42 0.03 2.77 0.06 4.65 0.05 DPA 7.54 0.16 3.35 0.26 4.19 0.16 DIPA 7.54 0.08 1.78 0.03 5.75 0.05 CHA 7.10 0.00 N/A (one phase) N/A (one phase)

TABLE-US-00005 TABLE 5 Volume of mixing results using 4 mL of solvent and 4 mL of a 100,000 ppm NaCl brine. n 3. Mixing Aqueous Organic Solvent Volume (mL) Volume (mL) Volume (mL) HA ~8 (gel formed) N/A (gel) N/A (gel) MPA 7.74 0.06 2.13 0.07 5.61 0.01 EBA 7.53 0.06 3.35 0.05 4.18 0.03 DPA 7.44 0.21 3.53 0.09 3.92 0.18 DIPA 7.68 0.03 3.18 0.02 4.51 0.05 CHA 7.23 0.06 N/A (one phase) N/A (one phase)

[0149] The study investigated if these V and T data could qualitatively indicate performance of the solvents for desalinating brines by testing all seven solvents for water recovery and desalination properties using a 100,000 ppm (1.71 M) NaCl brine. Table 6 shows the results. The results indicate there is a balance between water mass recovered and the salt rejection. While HA and CHA formed one phase at room temperature, separate phases were formed at 70 C. Their water mass recovered was significantly higher than the other solvents, but their salt rejections were negative, indicating an increase in salt concentration in the final purified water. Therefore, HA and CHA, which contain 10 amines and not 2 amines are not useful for TSSE. Aniline showed no results as expected with it being an aromatic 1 amine and more hydrophobic than the other solvents with a very different pK.sub.a value. MPA showed a higher water recovery, but the salt rejection was very low. With EBA, the water recovery reduced but the salt rejection increased by an order of magnitude compared to MPA. When the amine is moved to the center of the molecule, the salt rejection further increased. DIPA, the gold standard in the literature, also was the best performing solvent in these preliminary studies. The symmetry combined with the hindered amine appear to affect performance to some degree. Salt rejection was calculated using equation 6, where R is the rejection, C.sub.w70 is the concentration of salt in the water phase after 70 C., and C.sub.wi is the concentration of salt in the initial water phase added to the solvent. The water mass recovered was calculated using equation 5 described above.

[00013] $\begin{matrix} R = (1 - \frac{C_{w 70}}{C_{w i}}) 1 0 0 & (6) \end{matrix}$

TABLE-US-00006 TABLE 6 NaCl rejection (%), water mass recovered (%), and temperature change of mixing ( C.) of the solvents with 100,000 ppm NaCl brine. n 3. Water Mass Mixing Solvent Rejection (%) Recovered (%) T ( C.) HA 28.2 15.0 50.4 1.8 9.3 0.6 MPA 7.7 0.4 18.6 0.3 8.0 0.1 EBA 73.4 5.4 6.5 0.6 6.3 0.1 DPA 88.9 1.7 5.2 0.7 4.6 0.4 DIPA 83.6 3.0 9.2 0.5 5.6 1.2 CHA 15.4 2.5 25.9 6.4 9.0 1.0 Aniline N/A 0.0 0.0 0.3 0.5

[0150] Discussion. Based on molecular simulation data, the study benchmarked 59 different amine-based solvents against DIPA (currently one of the best-performing TSSE solvents) for potential use in TSSE brine desalination. To do this, the accuracy of MD based on a classical force field was explicitly evaluated by benchmarking against a polarizable force field and experimental liquid-liquid phase equilibria data. After establishing the reliability of the MD models, the study performed TSSE solvent screening by using a database of pure solvent thermophysical and thermodynamic properties, such as density, heat of vaporization, volumetric thermal expansion coefficient, and solvent-solvent binding free energy (all obtained by MD simulations). To aid the screening process, the k-means method was used to cluster the different solvents based on their evaluated thermodynamic properties. By doing so, 1 amines, long-chain/saturated cyclic solvents, unsaturated cyclic solvents, and 2 linear and branched amines were separated into different clusters.

[0151] It was believed that solvents grouped within the cluster containing DIPA would be effective candidates for TSSE. Additional interfacial water-solvent simulations were performed involving the solvents within the DIPA cluster. The interfacial system simulations indicate good performance of 2 amines with six carbons in a branched or linear structure, although worse performance was predicted for N-ethylbutan-1-amine and N-ethyl-2-methylpropan-1-amine within the evaluated amine solvents. Finally, although certain short-chain amine solvents were not predicted to perform well (due to the water and solvent mutual solubility), certain mixtures (e.g., of diisopropylamine and N-methylbutan-2-amine) were unexpectedly shown to perform better than pure DIPA.

[0152] Experimentally, it was shown that the symmetry of the six-carbon amine-containing molecule assisted with salt rejection. It was demonstrated that hindered solvents seem to have the best performing results so far.

TABLE-US-00007 TABLE 7 Label, SMILES string, name, and molecular structure of the screened amine-based solvents. Label Smile Name Structure M0 CC(C)NC(C)C diisopropylamine [00011] embedded image M1 CCCNCCC dipropylamine [00012] M2 CCCCNCC N-ethylbutan-1-amine [00013] M3 CCCCCCN hexan-1-amine [00014] M4 NC1CCCCC1 cyclohexanamine [00015] M5 NC1CCCCC1 aniline [00016] M6 CC1CCCCN1 2-methylpiperidine [00017] M7 CC1CCCNC1 3-methylpiperidine [00018] M8 CC1CCNCC1 4-methylpiperidine [00019] embedded image M9 CCCCCNC N-methylpentan-1-amine [00020] M10 CCCNC(C)C N-isopropylpropan-1-amine [00021] M11 CCNC(C)(C)C N-ethyl-2-methylpropan-2-amine [00022] M12 CCCCC(N)C hexan-2-amine [00023] M13 CC1CCC(C)N1 2,5-dimethyl-1H-pyrrole [00024] M14 CC1CC(C)CN1 2,4-dimethyl-1H-pyrrole [00025] M15 CCCC(N)CC hexan-3-amine [00026] embedded image M16 CCCCCNC N,2-dimethylbutan-2-amine [00027] M17 CCCNC(C)C N,2,2-trimethylpropan-1-amine [00028] M18 CCNCC(C)C N-ethyl-2-methylpropan-1-amine [00029] M19 CCNC(C)CC N-ethylbutan-2-amine [00030] M20 NCC1CCCC1 cyclopentylmenthanamine [00031] M21 CC1CCC(C)N1 2,5-dimethylpyrrolidine [00032] embedded image M22 CNC1CCCC1 N-methylcyclopentanamine [00033] M23 CC1CC(C)CN1 2,4-dimethylpyrrolidine [00034] M24 CC1C(C)CCN1 2,3-dimethylpyrrolidine [00035] M25 CC1(C)CCCN1 2,2-dimethylpyrrolidine [00036] M26 CC1(C)CCNC1 3,3-dimethylpyrrolidine [00037] M27 NC1C(C)CCC1 2-methylcyclopentan-1-amine [00038] embedded image M28 NC1CC(C)CC1 3-methylcyclopentan-1-amine [00039] M29 CCC1CCCN1 2-ethyl-1H-pyrrole [00040] M30 CCC1CNCC1 3-ethyl-1H-pyrrole [00041] M31 CC1C(C)CCN1 2,3-dimethyl-1H-pyrrole [00042] M32 NCCC1CCC1 2-cyclobutylethan-1-amine [00043] M33 CNCC1CCC1 1-cyclobutyl-N-methylmethanamine [00044] M34 CCNC1CCC1 N-ethylcyclobutanamine [00045] embedded image M35 CNCCC N-methylpropan-1-amine [00046] M36 CCNCC diethylamine [00047] M37 CNC(C)C N-methylpropan-2-amine [00048] M38 NCCCC butan-1-amine [00049] M39 CC(C)CN 2-methylpropan-1-amine [00050] M40 NC(C)CC butan-2-amine [00051] M41 CC(C)(N)C 2-methylpropan-2-amine [00052] M42 CN(C)CC N,N-dimethylethanamine [00053] embedded image M43 CNCCCC N-methylbutan-1-amine [00054] M44 CCNCCC N-ethylpropan-1-amine [00055] M45 CC(C)CNC N,2-dimethylpropan-1-amine [00056] M46 CNC(C)CC N-methylbutan-2-amine [00057] M47 CCNC(C)C N-ethylpropan-2-amine [00058] M48 CC(C)(C)NC N,2-dimethylpropan-2-amine [00059] M49 CCCCCN pentan-1-amine [00060] embedded image M50 NCC(C)CC 2-methylbutan-1-amine [00061] M51 CCC(N)CC pentan-3-amine [00062] M52 CC(C)CCN 3-methylbutan-1-amine [00063] M53 CC(N)CCC pentan-2-amine [00064] M54 CC(C)(C)CN 2,2-dimethylpropan-1-amine [00065] M55 CC(C)(N)CC 2-methylbutan-2-amine [00066] M56 C(C)CC(N)C pentan-2-amine [00067] embedded image M57 CN(C)CCC N,N-dimethylpropan-1-amine [00068] M58 CCN(C)CC N-ethyl-N-methylethanamine [00069] M59 CN(C)C(C)C N-Ndimethylpropan-2-amine [00070]

TABLE-US-00008 TABLE 8 Average density, volumetric thermal expansion coefficient (.sub.p), solvent-solvent binding free energy (w), fluid internal potential energy (U.sub.l), and heat of vaporization (H.sup.vap) evaluated at a temperature of 298 K. Density .sub.p W U.sub.l H.sup.vap Solvent (kg/m.sup.3) (10.sup.2K.sup.1) (kJ/mol) kJ/mol (kJ/mol) M0 753.783 0.133 1.116 66.139 37.759 M1 750.780 0.145 0.311 2.213 40.997 M2 754.465 0.130 0.203 21.623 42.736 M3 787.263 0.136 0.478 25.881 51.915 M4 902.106 0.112 2.165 14.434 50.978 M5 977.100 0.036 1.709 55.611 63.542 M6 870.705 0.120 2.083 12.744 43.858 M7 868.740 0.091 2.297 36.594 44.448 M8 858.291 0.114 1.834 60.223 43.612 M9 760.879 0.128 0.409 57.697 44.728 M10 754.071 0.135 0.674 39.726 39.508 M11 765.420 0.132 1.206 84.899 39.225 M12 785.256 0.132 0.662 26.138 48.201 M13 907.512 0.023 1.891 59.619 70.166 M14 916.876 0.067 2.388 50.272 60.771 M15 781.882 0.138 0.956 40.631 46.640 M16 778.821 0.122 1.767 78.013 40.031 M17 766.423 0.128 1.368 9.391 39.820 M18 753.657 0.145 0.612 5.679 40.581 M19 757.006 0.132 0.787 45.346 38.951 M20 884.997 0.111 1.622 83.100 50.666 M21 852.462 0.120 1.246 8.976 43.149 M22 860.357 0.123 1.106 68.656 44.916 M23 850.400 0.121 1.185 44.091 44.111 M24 856.200 0.122 1.462 29.297 44.715 M25 857.586 0.113 1.849 7.138 42.296 M26 858.170 0.123 2.237 80.231 40.790 M27 887.888 0.113 1.797 8.039 49.269 M28 886.271 0.118 1.971 34.561 50.445 M29 905.156 0.032 1.531 38.204 47.366 M30 912.118 0.027 1.911 15.724 25.145 M31 960.400 0.057 2.223 72.449 83.077 M32 887.360 0.109 1.054 41.704 54.940 M33 849.737 0.084 0.773 56.961 46.386 M34 848.756 0.105 0.708 6.100 45.554 M35 731.120 0.161 0.635 34.089 33.226 M36 729.932 0.168 0.614 1.409 32.151 M37 738.080 0.156 1.214 13.503 32.679 M38 764.234 0.153 1.066 14.830 39.880 M39 767.428 0.147 1.793 29.764 35.842 M40 765.104 0.148 1.390 54.446 36.543 M41 766.052 0.156 1.815 97.893 34.996 M42 722.271 0.148 1.520 35.732 30.975 M43 747.083 0.142 0.480 53.462 39.160 M44 741.830 0.141 0.453 1.776 37.522 M45 747.509 0.148 0.908 25.406 36.974 M46 752.835 0.137 1.133 17.959 36.149 M47 745.181 0.153 0.829 39.136 37.218 M48 764.143 0.147 1.839 65.703 35.399 M49 776.892 0.137 0.643 18.855 46.416 M50 780.899 0.143 1.546 10.144 42.900 M51 773.232 0.145 1.129 65.944 39.793 M52 784.341 0.133 1.054 31.718 45.498 M53 775.514 0.146 1.062 25.327 42.793 M54 787.933 0.140 2.501 58.253 39.784 M55 782.712 0.139 1.631 119.562 38.915 M56 774.562 0.135 1.038 28.627 41.399 M57 737.991 0.126 1.053 47.235 34.738 M58 741.798 0.133 1.330 7.673 35.736 M59 747.955 0.128 1.842 8.025 34.103

TABLE-US-00009 TABLE 9 [00014] $Solvation free energy of water in the evaluated solvents (_{w}^{}), solvent - water$ binding free energy (w.sup.sol-w), the average number of solvent-water H-bonds per solvent molecule (N.sub.HB), and the average number of sites solvent-water within the H-bond cutoff radius not H-bonded per solvent molecule (N.sub.NHB) for the mixture of the solvents with water at 298K. [00015] $_{w}^{}$ w.sup.sol-w Solvent (kJ/mol) (kJ/mol) N.sub.HB N.sub.NHB M0 17.88 2.93 0.85 0.96 M1 19.16 2.68 0.90 1.02 M2 19.43 2.08 0.98 1.13 M3 24.61 0.54 1.54 2.35 M4 23.41 1.66 1.50 2.27 M5 19.51 1.13 1.23 1.77 M6 17.35 1.08 0.88 1.13 M7 19.90 1.58 0.92 1.16 M8 18.45 1.18 0.97 1.28 M9 19.26 1.07 0.97 1.17 M10 19.66 2.74 0.90 1.01 M11 18.47 2.84 0.88 0.99 M12 22.99 0.99 1.38 2.07 M13 18.09 1.68 0.79 1.07 M14 18.11 1.39 0.68 1.01 M15 22.34 1.42 1.29 1.99 M16 19.22 1.74 0.92 1.09 M17 18.20 1.73 0.81 0.95 M18 18.78 2.45 0.83 0.93 M19 19.40 2.14 0.89 1.00 M20 24.44 1.12 1.50 2.27 M21 20.42 1.82 0.98 1.17 M22 19.84 1.16 1.01 1.21 M23 20.58 0.81 1.01 1.25 M24 20.90 0.81 1.03 1.26 M25 20.24 1.76 0.95 1.16 M26 18.61 1.58 0.89 1.15 M27 25.37 1.64 1.46 2.20 M28 24.67 1.72 1.50 2.26 M29 17.64 0.76 0.76 1.09 M30 17.07 0.97 0.67 1.11 M31 16.48 1.30 0.68 1.01 M32 24.22 0.98 1.57 2.39 M34 20.26 1.81 0.95 1.09 M35 20.96 1.54 1.00 1.19 M36 21.97 2.56 1.02 1.17 M37 21.80 1.66 1.02 1.21 M38 25.12 1.00 1.52 2.30 M39 25.65 1.63 1.38 2.08 M40 25.27 1.73 1.38 2.07 M41 25.09 2.06 1.37 2.00 M42 16.84 1.72 0.60 0.02 M43 20.03 1.15 0.99 1.20 M44 20.23 2.52 0.97 1.10 M45 20.10 1.46 0.90 1.07 M46 20.61 1.28 0.94 1.12 M47 20.48 2.49 0.96 1.08 M48 20.12 2.17 0.97 1.15 M49 24.36 0.86 1.53 2.31 M50 24.11 1.52 1.40 2.13 M51 24.00 1.61 1.28 1.96 M52 24.70 1.12 1.54 2.35 M53 24.15 1.42 1.42 2.15 M54 24.11 2.02 1.27 1.98 M55 24.02 2.17 1.28 1.90 M56 24.44 1.34 1.39 2.09 M57 15.22 0.91 0.53 0.01 M58 15.11 1.54 0.54 0.01

Example 2: Glycerol-Derived Solvents

[0153] Synthesizing Glycerol Derived Compounds. In many processes/applications, GDCs can be replacements for conventional organic solvents, while simultaneously offering enhancements arising from their low viscosity, tunable hydrophilicity/hydrophobicity, solvating power, and green origins..sup.11-12, 44-45 The general structure of several types of GDCs are displayed in FIG. 7 along with functional groups (R.sup.1, R.sup.2, and R.sup.3) that can be independently selected to control the physical, chemical, and thermodynamic properties of GDCs. The study has observed that although water can dissolve in GDCs, most GDCs have limited solubility in water, which is a highly advantageous behavior for designing effective solvents for TSSE. Epichlorohydrin is a convenient starting material, as it is a primary commodity chemical derived from glycerol but more reactive..sup.22-23 Glycidyl ethers also provide useful starting materials for the synthesis of GDCs for TSSE, and certain glycidyl ethers are already commercially available in large quantities. Furthermore, the production of GDCs directly from glycerol simultaneously eliminates the requirement for use of chlorinated reagents. Compounds with symmetric (e.g., R.sup.1=R.sup.2=R.sup.3) and asymmetric functional groups are synthesized and characterized to develop a rigorous understanding of the impact of functional group type and placement on relevant properties. From this, the impact of R groups on TSSE performance in GDC diether-alcohols (FIG. 7, panel a), triethers (FIG. 7, panel b), and diether-ketones (FIG. 7, panel c) can be measured. Furthermore, glycidyl ethers and amines are utilized to form GDCs with 2 amine groups to study solvents which compare directly to amines like DIPA. An example of this chemistry is shown in Scheme 1.

##STR00071##

[0154] Functional groups are modified to observe the effect the various groups impact specific performance targets, including combinations of properties such as high solubility of water, hydrophobicity/hydrophilicity, low ion solvation, and low viscosity..sup.50

[0155] Density Functional Theory Screening of GDCs. A suite of computational tools and descriptors have been developed that can be used to accelerate the investigation of large libraries of compounds and their thermophysical properties. Several different correlations have been developed that can be used to extract information from the electrostatic surface properties of individual molecules, based on first-principles density functional theory (DFT)..sup.54 Since the GDCs studied in this example are relatively small molecules comprised of light elements, the DFT calculations are fast (glycerol shown in FIG. 8 required a total of 9 CPU minutes for complete structural convergence). The resulting electrostatic properties are analyzed in terms of polarity (dipole moment, polarizability, etc.), and statistical analyses of the electrostatic potential were performed to make more detailed predictions about estimated solvation properties, viscosities, etc. These calculations can be easily automated to explore permutations in (R.sub.1, R.sub.2, and R.sub.3)-groups by generating a library of compounds as SMILES strings and feeding them into the DFT calculation engine.

[0156] Efficient and rigorous protocols for searching and optimizing small molecule structures by using a hierarchy of screening/relaxation stages have been developed. For instance, a large set of possible molecular structures are initially generated using the Molclus program..sup.55 These structures then serve as initial configurations for semi-empirical quantum mechanical optimizations using CREST.sup.56 and GFNO-xTB.sup.57-58 within the xTB program..sup.57 The relaxed structures are further optimized at a higher level with GFN2-xTB..sup.59 Next, single-point energy calculations of the lowest-energy configurations are performed at the B97-3c level.sup.60 using ORCA 4.2.0.sup.61-62 to extract fundamental properties/interactions (see FIG. 9).

[0157] Beyond just prediction/screening of the GDC thermophysical properties, it is also possible to provide more detailed information about the solvation mechanisms in these systems. These mechanistic details provide direct feedback about the most active sites within the GDC molecules, and thus, provide more rational synthetic pathways for tuning the solvent behavior.

[0158] Molecular Dynamics Screening of GDCs. Following the DFT-level screening of the individual molecules, larger-scale tests are performed via molecular dynamics (MD) simulations. Instead of merely analyzing a single isolated solvent molecule, the MD simulations allow the capture of a realistic bulk liquid environment. From short simulations of the bulk solvents, accurate estimates of the thermophysical properties of the system are made. Similar to the electrostatic analyses of the individual molecules, MD analyses are performed on the larger systems (i.e., 100s-1000s of molecules). Once equilibrated, instantaneous snapshots of the void spaces are taken in the solvent to generate a statistical representation of the void structure, and superimpose the electrostatic potential onto these void spaces in order to quantify the local electrostatic environment (felt by a solute molecule)..sup.63-65 These screening procedures are more efficient than directly calculating chemical potentials of different solutes or performing grand canonical Monte Carlo simulations. This screening hierarchy is used to make reliable predictions of properties such as Hansen solubility parameters, which can then be directly connected to experimental measurements and used to reduce experimental effort needed to identify the most promising molecules. FIG. 10 shows there will be a continuous feedback loop between computation and experiment to converge to optimized molecules (performance and economics) for brine desalination.

[0159] As the final stage in the simulation and modeling protocol, two-phase (i.e., organic+aqueous phases) MD simulations are performed of the liquid-liquid equilibria behavior. Since these systems involve multiple components and multiple phase equilibria, they are the most computationally demanding, but they provide the most representative model of the experimental system. One advantage of this model is that it promotes the direct tracking of the water transport from the brine phase to the solvent phase as a function of temperature, as well as solvent contamination in the aqueous phase. Furthermore, salt crystallization in the brine phase can be monitored, as the water molecules are depleted (raising the salt concentration).

[0160] The two-phase MD simulations have been tested with several different salt species (NaCl, KBr, KCl, and NaBr). Experimental benchmarking has confirmed that the MD simulations provide excellent qualitative performance predictions, with elevated values of water absorption in the solvent phase..sup.42 Furthermore, the simulations indicate that a dominant water absorption mechanism within the solvent phase is via hydrogen-bonding interactionsthereby identifying significant metrics for screening prototype solvent candidates.

[0161] In the two-phase MD simulations, the evaluation is extended beyond just the equilibrium thermodynamics and structures of these systems. The potential-of-mean force (PMF) required to transfer a water molecule from the brine phase to the solvent phase can also be calculated. This type of analysis provides a quantitative value for the free energy barrier (i.e., an estimate of the rate) to transfer a water molecule between phases (see FIG. 11). Similar to previous work,.sup.41,42 the distance between the center-of-mass of the water molecule and the solvent phase will be used as the reaction coordinate. The umbrella method and the weighted histogram analysis method are used to estimate the free energy based on the biased PMF simulations. A spacing of 0.15 nm between each simulation window and a spring constant of 1000 kJ/(mol.Math.m.sup.2) is sufficient to obtain an acceptable overlap of probability distributions.

[0162] The DFT-level screening is used to down-select solvent candidates, based on electrostatic descriptors, and the bulk solvent MD simulations will be used to further down-select the solvent candidates (based on bulk solvent structures, heat capacity, solvation free energies, etc.). These calculations are relatively fast, and much of the analysis can be automated. While it can be challenging to obtain quantitative predictions from these calculations, it has been shown.sup.27 that they are very effective for qualitative screening purposes (saving significant experimental time and expense). The two-phase MD simulations can as the primary bridge to the experimental systems, since tests analogous to the experimental performance evaluations can be performed. The models are designed to mimic the experimental testing protocols (brine-to-solvent phase volume ratios, brine compositions, temperature shifts, etc.). Output from these two-phase MD simulations provide critical information about the viability of the solvents for experimental testing. This includes water composition in solvent (at low and high temperatures), fraction of solvent in brine phase, composition of different species at the solvent-brine interface, etc.

[0163] Performance evaluate GDCs for brine desalination in TSSE using a NaCl brine. A protocol has been developed for solvent performance testing for brine desalination..sup.34 Solvent performance testing is done using temperature-controlled water baths. Solvents are used at room temperature (20-25 C.). The solvent is mixed with an equal volume of a 100 g/L (1.7 mol/L) NaCl solution. The solutions are allowed to equilibrate for 0.5-1 h. The solvent are separated from the concentrated brine using pipets. The water-laden solvent are heated to three temperatures (50, 65, 80 C.) to cause phase separation. The solvent and water phases are then separated using pipets. Promising solvents are tested for recyclability (repeating the same test) at least five times. Water content in solvents is analyzed using a Karl-Fischer titrator. Solvent content in water is analyzed with a total organic carbon analyzer or a UV-vis spectrophotometer depending on the GDC used. The bulk NaCl concentration in water is analyzed using a conductivity meter. Individual Na.sup.+ and Cl.sup. concentrations are measured using a Na.sup.+ selective electrode and a Cl.sup. selective electrode. The bulk NaCl, Na.sup.+, and Cl.sup. concentrations of the organic phase are measured using the same methods as above after evaporation of the organic solvent and dissolving the precipitated salt in a known quantity of water (e.g., 10 mL).

[0164] Performance evaluate GDCs for brine desalination in TSSE using other salt brines. Effective GDCs are further evaluated using 1.7 mol/L of NaBr, KCl, and KBr to have a consistent molar salt concentration as the NaCl studies to investigate how varying the cation and/or anion affects the equilibrium compositions of the biphasic mixture. All other TSSE testing variables remain the same. Water content in solvents is analyzed using a Karl-Fischer titrator. Solvent content in water is analyzed with a total organic carbon analyzer or a UV-vis spectrophotometer depending on the GDC used. The bulk salt concentrations in water is analyzed using a conductivity meter. Individual Na.sup.+, K.sup.+, and Cl.sup. concentrations are measured using a Na.sup.+ selective electrode, a K.sup.+ selective electrode, and a Cl.sup. selective electrode. Individual Br concentrations are measured using an ICP-OES. The bulk NaCl, Na.sup.+, K.sup.+, Cl.sup., and Br concentrations of the organic phase will be measured using the same methods as above after evaporation of the organic solvent and dissolving the precipitated salt in a known quantity of water (e.g., 10 mL).

[0165] Lastly, the GDC(s) that (1) dissolve 10 wt. % water at the lower operating temperature (20-25 C.), (2) dissolve in water at a concentration <500 ppm, (3) have a vapor pressure <10 mm Hg at 80 C. to have minimal solvent evaporative loss, and (4) have a projected toxicity LD.sub.50>300 mg/kg bodyweight, are tested with synthetic seawater brine. Synthetic seawater is purchased which conforms to ASTM standard D1141-98. The synthetic seawater is concentrated through a reverse osmosis membrane at 50% recovery to produce a synthetic brine to evaluate the GDC(s) for TSSE. All other TSSE testing variables will remain the same. Water content in solvents is analyzed using a Karl-Fischer titrator. Solvent content in water is analyzed with a total organic carbon analyzer or a UV-vis spectrophotometer depending on the GDC used. The bulk salt concentrations in water and the organic phase are analyzed using a conductivity meter. Optionally, individual ion concentrations can be measured using ion selective electrodes or ICP-OES as needed.

[0166] The following patents, applications and publications as listed below and throughout this document are hereby incorporated by reference in their entirety herein.

REFERENCES FOR EXAMPLE 1

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AMINE-BASED SOLVENTS FOR TEMPERATURE SWING SOLVENT EXTRACTION

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C02F1/265

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C07C215/10

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C07C217/04

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C02F2303/16

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B01D11/0492

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C02F1/26

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B01D11/04

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C07C215/10

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C07C217/04

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