Particulate crystalline nanocomposite as a sorbent for wastewater treatment
12491489 ยท 2025-12-09
Assignee
Inventors
Cpc classification
B01J20/3078
PERFORMING OPERATIONS; TRANSPORTING
B01J20/3204
PERFORMING OPERATIONS; TRANSPORTING
B01J20/3085
PERFORMING OPERATIONS; TRANSPORTING
B01J20/3236
PERFORMING OPERATIONS; TRANSPORTING
B01J20/3297
PERFORMING OPERATIONS; TRANSPORTING
C02F1/288
CHEMISTRY; METALLURGY
B01J20/28033
PERFORMING OPERATIONS; TRANSPORTING
B01J20/28061
PERFORMING OPERATIONS; TRANSPORTING
B01J20/06
PERFORMING OPERATIONS; TRANSPORTING
International classification
B01J20/06
PERFORMING OPERATIONS; TRANSPORTING
B01J20/28
PERFORMING OPERATIONS; TRANSPORTING
B01J20/30
PERFORMING OPERATIONS; TRANSPORTING
B01J20/32
PERFORMING OPERATIONS; TRANSPORTING
Abstract
A method of immobilizing contaminants disposed in an aqueous medium, the method comprising: contacting the aqueous medium with a particulate crystalline nanocomposite for a sufficient contact time to permit adsorption of the contaminants. The particulate crystalline nanocomposite comprises: a hexagonal lanthanum hydroxide (La(OH).sub.3) crystalline phase; a lanthanum oxide (La.sub.2O.sub.3) crystalline phase; a monoclinic calcium silicate (CaSiO.sub.3) crystalline phase; and, a graphitic carbon nitride (g-C.sub.3N.sub.4) crystalline phase, wherein at least a fraction of the g-C.sub.3N.sub.4 is in the form of mesoporous nanosheets.
Claims
1. A method of immobilizing contaminants disposed in an aqueous medium, the method comprising contacting the aqueous medium with a particulate crystalline nanocomposite for a sufficient contact time to permit adsorption of the contaminants, the particulate crystalline nanocomposite comprising: a hexagonal lanthanum hydroxide (La(OH).sub.3) crystalline phase; a lanthanum oxide (La.sub.2O.sub.3) crystalline phase; a monoclinic calcium silicate (CaSiO.sub.3) crystalline phase; and, a graphitic carbon nitride (g-C.sub.3N.sub.4) crystalline phase, wherein at least a fraction of the g-C.sub.3N.sub.4 is in the form of mesoporous nanosheets.
2. The method according to claim 1, wherein the contaminants comprise organic contaminants selected from the group consisting of: a polyaromatic hydrocarbon, a halogenated polyaromatic hydrocarbon; a phenol, a halogenated phenol; a furan, a halogenated furan; a dioxine, a halogenated dioxine; a biphenyl, a halogenated phenyl, and an organic dye.
3. The method according to claim 1, wherein the contaminants comprise inorganic contaminants selected from the group consisting of: a radioactive nuclide; a heavy metal; and, a metalloid.
4. The method according to claim 1, wherein the ratio by weight of CasiO.sub.3 to g-C.sub.3N.sub.4 to the sum of La(OH).sub.3 and La.sub.2O.sub.3 in the particulate crystalline nanocomposite is about (0.8-1.2):(0.8-1.2):(0.8-1.2).
5. The method according to claim 1, wherein the particulate crystalline nanocomposite comprises acicular particles of La(OH).sub.3, La.sub.2O.sub.3 and CaSiO.sub.3.
6. The method according to claim 1, wherein the particulate crystalline nanocomposite comprises acicular particles of La(OH).sub.3, La.sub.2O.sub.3 and CaSiO.sub.3 having a median length of from about 40 to about 100 nanometer (nm), as determined by Transmission Electron Microscopy.
7. The method according to claim 1, wherein at least about 80 weight percent (wt. %) of the g-C.sub.3N.sub.4 is in the form of mesoporous nanosheets.
8. The method according to claim 1, wherein the particulate crystalline nanocomposite has a surface area of from about 60 to about 100 square meters per gram (m.sup.2/g), as determined by Brunauer-Emmett-Teller (BET) analysis.
9. The method according to claim 1, wherein the particulate crystalline nanocomposite has a surface area of from about 70 to about 90 m.sup.2/g, as determined by BET analysis.
10. The method according to claim 1, wherein the particulate crystalline nanocomposite has an average pore diameter of from about 10 to about 25 nm, as determined by Barrett-Joyner-Halenda (BJH) desorption analysis.
11. The method according to claim 1, wherein the particulate crystalline nanocomposite has an average pore diameter of from about 10 to about 20 nm, as determined by BJH desorption analysis.
12. The method according to claim 1, wherein the particulate crystalline nanocomposite has a pore volume of from about 0.1 to about 0.4 cubic centimeters per gram (cm.sup.3/g), as determined by BJH desorption analysis.
13. The method according to claim 1, wherein the particulate crystalline nanocomposite has a pore volume of from about 0.1 to about 0.3 cm.sup.3/g, as determined by BJH desorption analysis.
14. The method according to claim 1, wherein the particulate crystalline nanocomposite has a hysteresis loop of Type H3 (IUPAC Classification), as determined by nitrogen (N.sub.2) adsorption-desorption analysis at 77 Kelvin (K).
15. The method according to claim 1 further comprising preparing the particulate crystalline nanocomposite by: forming a solution of a calcium salt and an alkali metal silicate in a solvent comprising water and a C.sub.1-C.sub.4 alkanol; heating the solution at a temperature of from about 150 to about 250 degrees Celsius (C) to form a dry product of CaSiO.sub.3; forming g-C.sub.3N.sub.4 by heating urea in a closed vessel at a temperature of from about 500 to about 700 C.; dispersing the CaSiO.sub.3, graphitic-C.sub.3N.sub.4 and La.sub.2O.sub.3 in a polar protic solvent and heating the dispersion at a temperature of from about 150 to about 250 C. at a pressure of from about 2 to about 8 bar; and, separating the solid crystalline nanocomposite from the heated dispersion.
16. The method according to claim 1, wherein the contact time of the aqueous medium with the particulate crystalline nanocomposite is from about 1 to about 120 minutes.
17. The method according to claim 1, wherein the contact time of the aqueous medium with the particulate crystalline nanocomposite is from about 5 to about 30 minutes.
18. The method according to claim 1, wherein a fixed volume of the aqueous medium is provided in which the particulate crystalline nanocomposite is dispersed.
19. The method according to claim 1, wherein a flow of the aqueous medium contacts a membrane in which the particulate crystalline nanocomposite is disposed.
20. The method according to claim 1, wherein the particulate crystalline nanocomposite is provided in an amount of from about 0.1 to about 5 grams per liter (g/L) of the aqueous medium.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) A more complete appreciation of this disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
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DETAILED DESCRIPTION
(17) Embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings wherever applicable, in that some, but not all, embodiments of the disclosure are shown.
(18) When describing the present disclosure, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.
(19) As used herein, the words a, an and the like generally carry a meaning of one or more, unless stated otherwise.
(20) Furthermore, the terms approximately, approximate, about, and similar terms generally refer to ranges that include the identified value within a margin of 20%, 10%, or preferably 5%, and any values therebetween.
(21) When amounts, concentrations, dimensions and other parameters are expressed in the form of a range, a preferable range, an upper limit value, a lower limit value or preferable upper and limit values, it should be understood that any ranges obtainable by combining any upper limit or preferable value with any lower limit or preferable value are also specifically disclosed, irrespective of whether the obtained ranges are clearly mentioned in the context.
(22) A weight percent of a component, unless specifically stated to the contrary, is based on the total weight of the formulation or composition in which the component is included. For example, if a particular element or component in a composition or article is said to have 5 wt. %, it is understood that this percentage is in relation to a total compositional percentage of 100%.
(23) As used herein, the term room temperature refers to a temperature range of 23 degrees Celsius ( C.)2 C. in the present disclosure. As used herein, ambient conditions means the temperature and pressure of the surroundings in which the substance, composition or article is located.
(24) The temperature parameters in the present application, if not specifically limited, are both allowed to be constant temperature processing and also allowed to be varied within a certain temperature interval. It should be understood that the constant temperature processing allows the temperature to fluctuate within the precision range of the instrument control. It is allowed to fluctuate in the range of, for example, 5 C., 4 C., 3 C., 2 C., or 1 C.
(25) As used herein, the term fraction refers to a numerical quantity which defines a part up to, but not including, 100 percent or the entirety of the thing in question.
(26) As used herein the term disposed refers to being positioned, placed, deposited, arranged or distributed in a particular manner.
(27) As used herein, the term number average molecular weight (Mn) and weight average molecular weight (Mw) are determined by gel permeation chromatography (GPC) with tetrahydrofuran (THF) as the eluent in accordance with DIN 55672-1:2007-08.
(28) As used herein, the term Scanning Electron Microscopy or SEM refers to a surface-imaging technique that produces images of a sample by scanning the sample with a focused beam of electrons. Unless otherwise specified, the SEM shall include all imaging techniques using electron beams for imaging.
(29) As used herein, the term high-resolution transmission electron microscopy (HRTEM) refers to a powerful imaging technique used to observe the fine details of materials at the atomic scale. In HRTEM, a high-energy electron beam is transmitted through a thin sample, and the transmitted electrons are used to form detailed images with extremely high resolution.
(30) As used herein, the term X-ray diffraction or XRD or X-ray crystallography refers to basic technique for obtaining information on the atomic structure of crystalline materials used as a standard laboratory technique. Unless otherwise specified, the XRD shall include an analytical technique based on the diffraction of X-rays by matter, especially for crystalline materials.
(31) As used herein with respect to X-ray diffraction analysis, JCPDS denotes the Joint Committee on Powder Diffraction Standards.
(32) The term unit cell as used herein refers to the smallest and simplest volume element (i.e., parallelpiped-shaped block) of a crystal that is completely representative of the unit or pattern of the crystal, such that the entire crystal can be generated by translation of the unit cell. The dimensions of the unit cell are defined by six numbers: dimensions a, b and c; and, angles , and (Blundel et al., 1976, Protein Crystallography, Academic Press, the disclosure of which is incorporated herein by reference in its entirety). A crystal is an efficiently packed array of many unit cells.
(33) The hexagonal crystalline phase is characterized by a right rhombic prism unit cell. This means the crystal structure can be described by a unit cell with two equal axes (a) and an included angle of 120 degrees (Y), while the third axis (c) is perpendicular to the plane formed by the two equal axes.
(34) The term triclinic crystalline phase refers to a crystal structure in which the unit cell is characterized by three mutually perpendicular aces of unequal length (abc) wherein further .
(35) An orthorhombic crystalline phase refers to a crystal structure having three mutually perpendicular axes of unequal lengths (abc) but wherein the crystal lattice forms a rectangular prism where the edges represent the three axes, all intersecting at 90-degree angles (===) 90.
(36) A cubic crystalline phase refers to a crystal structure where the unit cell is shaped like a cube, with three equal-length axes that are perpendicular to each other (at 90 angles). In this crystal system, the atoms or ions are arranged in a repeating pattern within the cubic lattice. The cubic crystalline structure is highly symmetric, possessing four threefold rotational axes and three fourfold rotational axes, permitting rotations of 90 around its specific axes and rotations of 120 about the body diagonals of the cube, while maintaining the same structure.
(37) A monoclinic crystalline phase refers to a crystal structure in which the unit cell of the material is characterized by three unequal axes, with two of them forming an angle that is not 90, while the third axis is perpendicular to the plane formed by the other two axes. In other words, the monoclinic crystal system has one axis that is tilted, resulting in a lack of orthogonality between all three axes. The unit cell in the monoclinic phase is thus asymmetrical, with distinct axial lengths and one non-90 angle.
(38) A tetragonal crystalline phase refers to a crystal structure in which the unit cell of the lattice has two axes of equal-length and a third axis that is of different length, but wherein all axes are at right angles (90) to each other. This crystal system may be represented as a square base (with two equal axes) and a height (the third axis) which is different, resulting in a rectangular prism-like shape. The tetragonal crystal structure possesses a four-fold rotational symmetry around its unique axis.
(39) As used herein, the term average crystallite size refers to the mean size of the crystalline domains or particles within a material. It is typically determined using X-ray diffraction (XRD) analysis, where the broadening of diffraction peaks is related to the size of the crystallites. The average crystallite size provides insight into the degree of crystallinity and the structural characteristics of the material. It is commonly expressed in nanometers (nm) and reflects the typical dimensions of the crystalline regions in the material, excluding any amorphous regions or defects.
(40) As used herein, the term particle refers to a small object that acts as a whole unit with regard to its transport and properties. As used herein, nanoparticles-sometimes contracted herein to NPs-refers to particles having a particle size of 1 nanometer (nm) to 1000 nm.
(41) Unless otherwise stated, the term particle size refers to the largest axis of the particle. In the case of a generally spherical particle, the largest axis is the diameter.
(42) The term median volume particle size (Dv50), as used herein, refers to a particle size corresponding to 50% of the volume of the sampled particles being greater than and 50% of the volume of the sampled particles being smaller than the recited Dv50 value. Similarly, if used, the term Dv90 refers to a particle size corresponding to 90% of the volume of the sampled particles being smaller than and 10% of the volume of the sampled particles being greater than the recited Dv90 value. Particle size is determined herein by Scanning Electron Microscopy (SEM).
(43) As used herein, the term nanocomposite refers to a composite material in which at least one dimension of a component thereof is in the nanometer size scale (<100 nm). The nanocomposites are thus poly-phase solid materials made up of two or more nanomaterials. The term includes all types of multiphase solid material in which one of the phases has one, two, or three dimensions of less than 100 nm, or structures having nanoscale repeat distances between the different phases that make up the material.
(44) As used herein, the term porosity refers to a measure of the void or vacant spaces within a material. As used herein, the term pore volume refers to the total volume of void spaces (pores) within a material that is capable of being filled by a gas or liquid: it is typically expressed in cubic centimeters per gram (cm.sup.3/g). As used herein, the term pore diameter refers to the median width or size of the pores (void spaces) within a material, typically measured in nm or angstroms ().
(45) Pores may be micropores, mesopores, macropores, and/or a combination thereof. The pores exist in the bulk material, not necessarily in the molecular structure of the material. The term microporous means that particulate crystalline nanocomposite have pores with an average pore width (i.e., diameter) of less than 2 nm. The term mesoporous means the pores of the nanocomposite have an average pore width of 2-50 nm. The term macroporous means the pores of the nanocomposite have an average pore width larger than 50 nm. Pore size may be determined by methods including, but not limited to, gas adsorption (e.g., N.sub.2 adsorption), mercury intrusion porosimetry, and imaging techniques such as SEM and X-ray computed tomography (XRCT).
(46) Having regard to a parameter distribution of the disclosed material, the term monomodal references only one peak being observed in a frequency distribution graph of said parameter. The term polymodal references a distribution with two or more distinct peaks or modes. The terms bimodal and trimodal may be utilized herein to reference the presence of two or three modes, respectively.
(47) As used herein, the Brunauer-Emmett-Teller (BET) analysis references the method of measuring the specific surface area (m.sup.2/g) of a solid material via the adsorption of gas molecules onto the surface of the solid, as detailed in standard NF ISO 5794-1, Appendix E (June 2010).
(48) As used herein, the Barrett, Joyner, and Halenda (BJH) desorption analysis refers to the method of determining the volume of mesopores per unit mass (mL/g) of a solid material utilizing the adsorption and desorption isotherms associated with gas molecules inside the mesopores of the solid, as detailed in Technical Standard DIN 66134:1998-02.
(49) As used herein, the term porous particulate nanocomposite refers to a material composed of discrete particles that form a structure with interconnected pores or voids. These pores allow for the passage of fluids or gases, contributing to the material's overall porosity. The composite typically consists of two or more distinct phases, which may include various inorganic or organic components, and is characterized by its unique morphology, such as irregularly shaped particles or aggregates.
(50) The term graphitic carbon nitride often abbreviated to g-C.sub.3N.sub.4, refers to a family of carbon nitride compounds with a layered structure similar to graphene. Graphitic carbon nitride may be considered a synthetic polymer primarily composed of carbon and nitrogen, with some hydrogen impurities. In certain embodiments, the graphitic carbon nitride (g-C.sub.3N.sub.4) may be present in at least one of the following morphologies: nanorectangles; nanotriangles; nanopentagons; nanohexagons; nanoribbons; nanosheets; nanodiscs; nanoflakes; nanofoils; and, nanobelts.
(51) As used herein, the term metalloid refers to a type of element that has properties intermediate between those of metals and nonmetals. Metalloids typically exhibit characteristics such as the ability to conduct electricity and they can form alloys with metals.
(52) The term powder, as used herein, means a composition that consists of finely dispersed solid particles that are free-flowing.
(53) The term dry as used herein means comprising less than 5 wt. % of any compound or composition being in liquid form when measured at 25 C. under ambient conditions. For instance, the term dry includes comprising less than 3 wt. %, less than 2 wt. %, less than 1%, or even about 0% of said compound or composition being in liquid form when measured at 25 C. under ambient conditions. Exemplary such compounds or compositions include water, oils, organic solvents and other wetting agents.
(54) The term polar solvent as used herein refers to a solvent having a dielectric constant (8) of more than 5 as measured at 25 C. The determination of dielectric constant (8) is known in the art: the use of measured voltages across parallel plate capacitors in such determinations may be mentioned. The term polar solvent may encompass both aprotic and protic solvents, wherein protic solvents are those solvents which are capable of yielding or accepting a proton and aprotic solvents are those solvents that do not yield or accept a proton.
(55) Water, for use as a (co-)solvent or diluent herein, is intended to mean water of low solids content as would be understood by a person of ordinary skill in the art. The water may, for instance, be distilled water, demineralized water, deionized water, reverse osmosis water, boiler condensate water, or ultra-filtration water. Tap water may be tolerated in certain circumstances.
(56) As used herein, comminuting refers to process of reducing the average size of solid materials into smaller particles, by crushing, grinding, cutting, vibrating, or other processes.
(57) The term hydrolysis, as used herein, is the chemical reaction of a molecule with water to produce two or more smaller molecules.
(58) As used herein, hydrogen generation rate (HGR) refers to the amount of hydrogen gas produced per unit of time during a chemical reaction.
(59) The term sonication refers to a process that uses sound energy (sonic waves) to agitate particles in a sample. As used herein, the term ultrasonication refers to irradiation with ultrasonic waves having a frequency of at least 20 kHz. Without intention to limit the present disclosure, (ultra)sonication may be performed using an (ultra)sonic bath or an (ultra)sonic probe.
(60) As used herein, the term calcination refers to a thermal treatment process which is conducted in the absence of, or under a restricted supply of ambient oxygen. This is performed to remove impurities or volatile substances and/or to induce thermal decomposition or a change in the thermally treated material.
(61) The term actinic radiation includes light with wavelengths of electromagnetic radiation ranging from the ultraviolet (UV) light range, through visible light range, and into the infrared range. Actinic radiation generally has a wavelength of from 150 to 2000 nm.
(62) As used herein, the term membrane refers to a porous structure that is capable of separating components of a homogeneous or heterogeneous fluid. In particular, pores in the sense of a membrane indicate voids permitting fluid communication between different sides of the structure. More particularly in use, when a homogeneous or heterogeneous fluid is passed through the membrane, some components of the fluid can pass through the pores of the membrane into a permeate stream, some components of the fluid can be retained by the membrane and can thus accumulate in a retentate and/or some components of the fluid can be rejected by the membrane into a rejection stream. It is not precluded in the present disclosure that both the retenate and the permeate can constitute valuable materials that can be subject to further processing, if required.
(63) Membranes can be of various thicknesses, with homogeneous or heterogeneous structures. The membranes of the present disclosure are neutral or uncharged, and particle transport is considered to be passive, which passive transport can be facilitated by pressure, concentration, and chemical or electrical gradients of the filtration process.
(64) As used herein, the term filtration refers to a mechanical or physical operation that can be employed for the separation of constituents of homogeneous or heterogeneous solutions. Types of filtration can be categorized based on the estimated sizes of chemicals to be separated and can involve particle filtration (>10 micrometer (m)); microfiltration (0.1-10 m); ultrafiltration (0.01-0.1 m); nanofiltration (NF) (0.001-0.01 m); and, reverse osmosis, or RO (<0.001 m).
(65) As used herein, the term permeate refers to a filtered liquid that passes through a membrane during a filtration process, leaving behind larger particles or contaminants.
(66) The term shear rate as used herein, references the rate of increase in the velocity of a fluid flowing in the x direction per unit distance in the orthogonal y direction. The shear rate has units of reciprocal time (s.sup.1).
(67) As used herein, C.sub.1-C.sub.n alkyl group refers to a monovalent group that contains from 1 to n carbons atoms, that is a radical of an alkane and includes straight-chain and branched organic groups. As such, a C.sub.1-C.sub.4 alkyl group refers to a monovalent group that contains from 1 to 4 carbons atoms, that is a radical of an alkane and includes straight-chain and branched organic groups. Examples of alkyl groups include, but are not limited to: methyl; ethyl; propyl; isopropyl; n-butyl; isobutyl; sec-butyl; and, tert-butyl. In the present disclosure, such alkyl groups may be unsubstituted or may be substituted with one or more halogen. Where applicable for a given moiety (R), a tolerance for one or more non-halogen substituents within an alkyl group will be noted in the specification.
(68) In addition, the present disclosure is intended to include all isotopes of atoms occurring in the present compounds and complexes. Isotopes include those atoms having the same atomic number but different mass numbers. By way of general example, and without limitation, isotopes of hydrogen include deuterium and tritium, and isotopes of carbon include .sup.13C and .sup.14C. Isotopes of oxygen include .sup.16O, .sup.17O, and .sup.18O. Isotopically-labelled compounds of the disclosure may generally be prepared by conventional techniques known to those skilled in the art or by processes analogous to those described herein, using an appropriate isotopically-labelled reagent in place of the non-labelled reagent otherwise employed.
(69) The present disclosure is intended to include all hydration states of a given compound or formula, unless otherwise noted or when heating a material.
(70) Aspects of this disclosure are directed to a method of water purification using a particulate crystalline nanocomposite of lanthanum hydroxide (La(OH).sub.3), lanthanum oxide (La.sub.2O.sub.3), calcium silicate (CaSiO.sub.3), and graphitic carbon nitride (g-C.sub.3N.sub.4). The nanocomposite material fabricated by the method of the present disclosure achieves a multi-phase crystalline structure with controlled morphology and enhanced structural properties for wastewater treatment.
(71) A method of immobilizing contaminants disposed in an aqueous medium is described. In some embodiments, the contaminants include organic contaminants selected from the group consisting of a polyaromatic hydrocarbon, a halogenated polyaromatic hydrocarbon, a phenol, a halogenated phenol, a furan, a halogenated furan, a dioxine, a halogenated dioxine, a biphenyl, a halogenated phenyl, and an organic dye. In some embodiments, the contaminants comprise inorganic contaminants selected from the group consisting of radioactive nuclide, a toxic metal, a heavy metal and a metalloid.
(72) In some embodiments, the organic contaminant may be a dye, a phenol, a polycyclic aromatic hydrocarbon, an herbicide, a pesticide, a persistent organic contaminant, or the like.
(73) A dye is a colored substance that chemically binds to a material it may be intended to color. Generally, a dye is applied in solution, typically aqueous solution. Examples of dyes include, but are not limited to: acridine dyes, which are acridine and its derivatives such as acridine orange, acridine yellow, acriflavine, and gelgreen; anthraquinone dyes, which are anthroaquinone and its derivatives such as acid blue 25, alizarin, anthrapurpurin, carminic acid, 1,4-diamno-2,3-dihydroanthraquinone, 7,14-dibenzypyrenequinone, dibromoanthrone, 1,3-dihydroxyanthraquinone, 1,4-dihydroxyanthraquinone, disperse red 9, disperse red 11, indanthrone blue, morindone, oil blue 35, parietin, quinizarine green SS, remazol brilliant blue R, solvent violet 13, 1,2,4-trihydroxyanthraquinone, vat orange 1, and vat yellow 1; diaryl methane dyes such as auramine O, triarylmethane dyes such as acid fuchsin, aluminon, aniline blue WS, aurin, aurintricarboxylic acid, brilliant blue FCF, brilliant green, bromocresol green, bromocresol purple, bromocresol blue, bromophenol blue, bromopyrogallol red, chlorophenol red, coomassie brilliant blue, cresol red, O-cresolphthalein, crystal violet, dichlorofluorescein, ethyl green, fast green FCT, FIASH-EDT2, fluoran, fuchsine, green S, light green SF, malachite green, merbromin, metacresol purple, methyl blue, methyl violet, naphtholphthalein, new fuchsine, pararosaniline, patent blue V, phenol red, phenolphthalein, phthalein dye, pittacal, spirit blue, thymol blue, thymolphthalein, Victoria blue BO, Victoria blue R, water blue, xylene cyanol, and xylenol orange; azo dyes such as acid orange 5, acid red 13, alican yellow, alizarine yellow R, allura red AC, amaranth, amido black 10B, aniline yellow, arylide yellow, azo violet, azorubine, basic red 18, biebrich scarlet, Bismarck brown Y, black 7984, brilliant black BN, brown FK, chrysoine resorcinol, citrus red 2, congo red, D&C red 33, direct blue 1, disperse orange 1, eriochrome black T, evans blue, fast yellow AB, orange 1, hydroxynaphthol blue, janus green B, lithol rubine BK, metanil yellow, methyl orange, methyl red, methyl yellow, mordant brown 33, mordant red 19, naphthol AS, oil red O, oil yellow DE, orange B, orange G, orange GGN, para red, pigment yellow 10, ponceau 2R, prontosil, red 2G, scarlet GN, Sirius red, solvent red 26, solvent yellow 124, sudan black B, sudan I, sudan red 7B, sudan stain, tartrazine, tropaeolin, trypan blue, and yellow 2G; phthalocyanine dyes such as phthalocyanine blue BN, phthalocyanine Green G, Alcian blue, and naphthalocyanine; azin dyes such as basic black 2, mauveine, neutral red, Perkin's mauve, phenazine, and safranin; indophenol dyes such as indophenol and dichlorophenolindophenol; oxazin dyes; oxazone dyes; thiazine dyes such as azure A, methylene blue, methylene green, new methylene blue, and toluidine blue; thiazole dyes such as primuline, stains-all, and thioflavin; xanthene dyes such as 6-carboxyfluorescein, eosin B, eosin Y, erythosine, fluorescein, rhodamine B, rose bengal, and Texas red; fluorone dyes such as calcein, carboxyfluorescein diacetate succinimidyl ester, fluo-3, fluo-4, indian yellow, merbromin, pacific blue, phloxine, and seminaphtharhodafluor; or rhodamine dyes such as rhodamine, rhodamine 6G, rhodamine 123, rhodamine B, sulforhodamine 101, and sulforhodamine B.
(74) A phenol is an organic compound consisting of a hydroxyl group (OH) bonded directly to an aromatic hydrocarbon group. Examples of phenols include, but are not limited to, phenol (the namesake of the group of compounds), bisphenols (including bisphenol A), butylated hydroxytoluene (BHT), 4-nonylphenol, orthophenyl phenol, picric acid, phenolphthalein and its derivatives mentioned above, xylenol, diethylstilbestrol, L-DOPA, propofol, butylated hydroxyanisole, 4-tert-butylcatechol, tert-butylhydroquinone, carvacrol, chloroxyleol, cresol (including M-, O-, and P-cresol), 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butylphenol, 2-ethyl-4,5-dimethylphenol, 4-ethylguaiacol, 3-ethylphenol, 4-ethylphenol, flexirubin, mesitol, 1-nonyl-4-phenol, thymol, 2,4,6-tri-tert-butylphenol, chlorophenol (including 2-, 3-, and 4-chlorophenol), dichlorophenol (including 2,4- and 2,6-dichlorophenol), bromophenol, dibromophenol (including 2,4-dibromophenol), nitrophenol, norstictic acid, oxybenzone, and paracetamol (also known as acetoaminophen).
(75) A polycyclic aromatic hydrocarbon (PAH) is an aromatic hydrocarbon composed of multiple aromatic rings. Examples of polycyclic aromatic hydrocarbons include naphthalene, anthracene, phenanthrene, phenalene, tetracene, chrysene, triphenylene, pyrene, pentacene, benzo[a]pyrene, corannulene, benzo[g,h,i]perylene, coronene, ovalene, benzo[c]fluorine, acenaphthene, acenaphthylene, benz[a]anthracene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, cyclopenta[c,d]pyrene, dibenz[a,h]anthracene, dibenzo[a,e]pyrene, dibenzo[a,h]pyrene, dibenzo[a,i]pyrene, dibenzo[a,1]pyrene, fluoranthene, fluorine, indeno[1,2,3-c,d]pyrene, 5-methylchrysene, naphthacene, pentaphene, picene, and biphenylene.
(76) An herbicide is a substance that is toxic to plants and may kill, inhibit the growth of, or prevent the germination of plants. Herbicides are typically used to control the growth of or remove unwanted plants from an area of land, particularly in an agricultural context. Examples of herbicides include, but are not limited to, 2,4-D, aminopyralid, chlorsulfuron, clopyralid, dicamba, diuron, glyphosate, hexazinone, imazapic, imazapyr, methsulfuron methyl, picloram, sulfometuron methyl, triclopyr, fenoxaprop, fluazifop, quizalofop, clethodim, sethoxydim, chlorimuron, foramsulfuron, halosulfuron, nicosulfuron, primisulfuron, prosulfuron, rimsulfuron, thofensulfuron, tribenuron, imazamox, imazaquin, flumetsulam, cloransulam, thiencarbazone, fluoxpyr, diflufenzopyr, atrazine, simazine, metribuzin, bromoxynil, bentazon, linuron, glufosinate, clomazone, isoxaflutole, topramezone, mesotrione, tembotrione, acifluorfen, formesafen, lactofen, flumiclorac, flumioxazin, fulfentrazone, carfentrazone, fluthiacet-ethyl, falufenacil, paraquat, ethalfluralin, pendimethalin, trifluralin, butylate, EPTC, ecetochlor, alachlor, metolachlor, dimethenamid, flufenacet, and pyroxasulfone.
(77) A pesticide is a substance meant to prevent, destroy, or control pests including, but not limited to algae, bacteria, fungi, plants, insects, mites, snails, rodents, and viruses.
(78) A pesticide intended for use against algae is known as an algicide. Examples of algicides include benzalkonium chloride, bethoxazin, cybutryne, dichlone, dichlorophen, diuron, endothal, fentin, isoproturon, methabenthiazuron, nabam, oxyfluorfen, pentachlorophenyl laurate, quinoclamine, quinonamid, simazine, terbutryn, and tiodonium.
(79) A pesticide intended for use against bacteria is known as a bactericide. Examples of bactericides include antibiotics such as: aminoglycosides such as amikacin, gentamicin, kanamycin, neomycin, netilmicin, tobramycin, paromomycin, streptomycin, and spectinomycin; ansamycins such as geldanamycin, herbimycin, and rifaximin; carbacephems such as loracarbef; carbapenems such as ertapenem, doripenem, imipenem, and meropenem; cephalosporins such as cefadroxil, cefazolin, cephradine, cephapirin, cephalothin, cephalexin, cefaclor, cefoxitin, cefotetan, cefamandole, cefmetazole, cefonicid, cefprozil, cefuroxime, cefixime, cefdinir, cefditoren, cefoperazone, cefotaxime, cefpodoxime, cefazidime, ceftibuten, ceftizoxime, moxalactam, ceftriaxone, cefepime, cefaroline fosamil, and ceftobiprole; glycopeptides such as teicoplanin, vancomycin, telavancin, dalbavancin, and oritavancin; lincosamides such as clindamycin and lincomycin; lipopeptides such as daptomycin; macrolides such as azithromycin, clarithromycin, erythromycin, roxithromycin, telithromycin, spiramycin, and fidoxamicin; monobactams such as aztreonam; nitrofurans such as furazolidone and nitrofurantoin; oxazolidinones such as linezolid, posizolid, radezolid, and torezolid; penicillins such as amoxicillin, ampicillin, azlocillin, dicloxacillin, flucloxacillin, mezlocillin, methicillin, nafcillin, oxacillin, penicillins (including penicillin G and V), piperacillin, temocillin, and ticarcillin; polypeptides such as bacitracin, colistin, and polymyxin B; quinolones such as ciproflaxacin, enoxacin, gatifloxacin, gemifloxacin, levofloxacin, lomefloxacin, moxifloxacin, nadifloxacin, nalidixic acid, norfloxacin, ofloxacin, trovafloxacin, gepafloxacin, sparfloxacin, and temafloxacin; sulfonamides such as mafenide, sulfacetamide, sulfadiazine, sulfadithoxine, sulfamethizole, sulfamethoxazole, sulfanilamide, sulfasalazine, sulfisoxazole, and sulfonamidochrysoidine; tetracyclines such as demeclocycline, doxycycline, metacycline, minocycline, oxytetracycline, and tetracycline.
(80) A pesticide intended for use against fungi is known as a fungicide. Examples of fungicides include acibenzolar, acypetacs, aldimorph, anilazine, aureofungin, azaconazole, azithiram, azoxystrobin, benalaxyl, benodanil, benomyl, benquinox, benthiavalicarb, binapacryl, biphenyl, bitertanol, bixafen, blasticidin-S, boscalid, bromuconazole, captafol, captan, carbendazim, carboxin, carpropamid, chloroneb, chlorothalonil, chlozolinate, cyazofamid, cymoxanil, cyprodinil, dichlofluanid, diclocymet, dicloran, diethofencarb, difenoconazole, diflumetorim, dimethachlone, dimethomorph, diniconazole, dinocap, dodemorph, edifenphos, enoxastrobin, epoxiconazole, etaconazole, ethaboxam, ethirimol, etridiazole, famoxadone, fenamidone, fenarimol, fenbuconazole, fenfuram, fenhexamid, fenoxanil, fenpropidin, fenpropimorph, ferbam, fluazinam, fludioxonil, flumorph, fluopicolide, fluopyram, fluoroimide, fluoxastrobin, flusilazole, flutianil, flutolain, flopet, fthalide, furalaxyl, guazatine, hexaconazole, hymexazole, imazalil, imibenconazole, iminoctadine, iodocarb, ipconazole, iprobenfos, iprodione, iprovalicarb, siofetamid, isoprothiolane, isotianil, kasugamycin, laminarin, mancozeb, mandestrobin, mandipropamid, maneb, mepanypyrim, mepronil, meptyldinocap, mealaxyl, metominostrobin, metconazole, methafulfocarb, metiram, metrafenone, myclobutanil, naftifine, nuarimol, octhilinone, ofurace, orysastrobin, oxadixyl, oxathiapiprolin, oxolinic acid, oxpoconazole, oxycarboxin, oxytetracycline, pefurazate, penconazole, pencycuron, penflufen, penthiopyrad, phenamacril, picarbutrazox, picoxystrobin, piperalin, polyoxin, probenzole, prochloraz, procymidone, propamocarb, propiconazole, propineb, proquinazid, prothiocarb, prothioconazole, pydiflumetofen, pyraclostrobin, pyrametostrobin, pyraoxystrobin, pyrazophos, pyribencarb, pyributicarb, pyrifenox, pyrimethanil, pyrimorph, pyriofenone, pyroquilon, quinoxyfen, quintozene, sedaxane, silthiofam, simeconazole, spiroxamine, streptomycin, tebuconazole, tebufloquin, teclofthalam, tecnazene, terbinafine, tetraconazole, thiabendazole, thifluzamide, thiphanate, thiram, tiadinil, tolclosfos-methyl, folfenpyrid, tolprocarb, tolylfluanid, triadimefon, triadimenol, triazoxide, triclopyricarb, tricyclazole, tridemorph, trifloxystrobin, triflumizole, triforine, validamycin, and vinclozolin.
(81) A pesticide intended for use against plants is known as an herbicide as described above.
(82) A pesticide intended for use against insects is known as an insecticide. Examples of insecticides are: organochlorides such as Aldrin, chlordane, chlordecone, DDT, dieldrin, endofulfan, endrin, heptachlor, hexachlorobenzene, lindane, methoxychlor, mirex, pentachlorophenol, and TDE; organophosphates such as acephate, azinphos-methyl, bensulide, chlorethoxyfos, chlorpyrifos, diazinon, chlorvos, dicrotophos, dimethoate, disulfoton, ethoprop, fenamiphos, fenitrothion, fenthion, malathion, methamdophos, methidathion, mevinphos, monocrotophos, naled, omethoate, oxydemeton-methyl, parathion, phorate, phosalone, phosmet, phostebupirim, phoxim, pirimiphos-methyl, profenofos, terbufos, and trichlorfon; carbamates such as aldicarb, bendiocarb, carbofuran, carbaryl, dioxacarb, fenobucarb, fenoxycarb, isoprocarb, methomyl; pyrethroids such as allethrin, bifenthrin, cyhalothrin, cypermethrin, cyfluthrin, deltamethrin, etofenprox, fenvalerate, permethrin, phenothrin, prallethrin, resmethrin, tetramethrin, tralomethrin, and transfluthrin; neonicotinoids such as acetamiprid, clothiandin, imidacloprid, nithiazine, thiacloprid, and thiamethoxam; ryanoids such as chlorantraniliprole, cyanthaniliprole, and flubendiamide.
(83) A pesticide intended for use against mites is known as a miticide. Examples of miticides are permethrin, ivermectin, carbamate insecticides as described above, organophosphate insecticides as described above, dicofol, abamectin, chlorfenapyr, cypermethrin, etoxazole, hexythiazox, imidacloprid, propargite, and spirotetramat.
(84) A pesticide intended for use against snails and other mollusks is known as a molluscicide. Examples of molluscicides are metaldehyde and methiocarb.
(85) A pesticide intended for use against rodents is known as a rodenticide. Examples of rodenticides are warfarin, coumatetralyl, difenacoum, brodifacoum, flocoumafen, bromadiolone, diphacinone, chlorophacinone, pindone, difethialone, cholecalciferol, ergocalciferol, ANTU, chloralose, crimidine, 1,3-difluoro-2-propanol, endrin, fluroacetamide, phosacetim, pyrinuron, scilliroside, strychnine, tetramethylenedisulfotetramine, bromethalin, 2,4-dinitrophenol, and uragan D2.
(86) A pesticide intended for use against viruses is known as a virucide. Examples of virucides are cyanovirin-N, griffithsin, interferon, NVC-422, scytovirin, urumin, virkon, zonroz, and V-bind viricie.
(87) A persistent organic contaminant is a toxic organic chemical that adversely affects human and environmental health, can be transported by wind and water, and can persist for years, decades, or centuries owing to resistance to environmental degradation by natural chemical, biological, or photolytic processes. Persistent organic contaminants are regulated by the United Nations Environment Programme 2001 Stockholm Convention on Persistent Organic Contaminants. Examples of persistent organic contaminants are Aldrin, chlordane, dieldrin, endrin, heptachlor, hexachlorobenzene, mirex, toxaphene, polychlorinated biphenyl (PCBs), dichlorodiphenyltrichloroethane (DDT), dioxins, polychlorinated dibenzofurans, chlordecone, hexachlorocyclohexane (- and -), hexabromodiphenyl ether, lindane, pentachlorobenzene, tetrabromodiphenyl ether, perfluorooctanesulfonic acid, endosulfans, and hexabromocyclododecane.
(88) The method of immobilizing contaminants disposed in an aqueous medium of the present disclosure requires that aqueous medium to be brought into contact with the particulate nanocomposite material for a sufficient contact time to permit adsorption of the contaminants concerned. Without intention to limit the present disclosure, the contact time aqueous medium with the particulate crystalline nanocomposite may be from about 1 to about 120 minutes, for example from about 1 to 90 minutes, from about 1 to 60 minutes, from about 1 to 30 minutes or from about 5 to about 30 minutes. Independently of, or in addition to the aforementioned exemplary contact time, the particulate crystalline nanocomposite may be provided in an amount ranging from about 0.1 to about 5 grams per liter of the aqueous medium for said contacting. For example, the particulate crystalline nanocomposite may be provided in an amount of from about 2 to about 5 grams per liter, from about 3 to about 5 grams per liter or from about 4 to about 5 grams per liter of the aqueous medium.
(89) The aqueous medium may be provided as a static volume in which the nanocomposite material is dispersed. In an alternative embodiment, the aqueous medium may be provided as a fixed volume in which the nanoparticulate is dispersed but which is subjected to agitation: the nanoparticulate material may be suspended in the volume or may be constrained within a bed or membrane or by a support. In a further non-limiting alternative, the aqueous medium may be provided as a flow which contacts the particulate nanocomposite material. In this embodiment, the particulate nanocomposite material may need to constrained within a bed or, more particularly, a membrane which the aqueous medium contacts as either a perpendicular or tangential (cross-) flow stream.
(90) Perpendicular flow filtration may be preferred where the aqueous medium feed is characterized by a low concentration of particulates given that there would be reduced residue build up on the surface of the membrane during filtration. Whilst perpendicular flow filtration may be performed continuously, it is preferably performed in a batch or semi-continuous manner, permitting the membrane to be cleaned between use cycles to remove residue build-up.
(91) As noted, membrane separation by tangential flow filtration is not precluded in the present disclosure where the membrane comprises the afore-described particulate nanocomposite material. Conventionally, the retentate stream in tangential flow filtration is recycled. It is also typical for tangential flow filtration to be performed as a continuous process because a constant flow of the feed stream across the surface of the ultrafiltration membrane may prevent the accumulation of residues on the surface thereof.
(92) Where membrane filtration of the aqueous medium is conducted by tangential flow filtration, the feed of the aqueous medium may be represented as a laminar flow and thereby characterized by a shear rate. The shear rate of the aqueous medium may typically be from about 1000 to about 10000 s.sup.1, for example from about 2000 to about 10000 s.sup.1, from about 2000 to about 8000 s.sup.1 or from about 4000 to about 8000 s.sup.1.
(93) Independently of the use of direct flow or tangential flow filtration where a membrane comprising the particulate nanocomposite material is utilized, the step of contacting may preferably be performed at a transmembrane pressure differential, specifically a pressure difference between the retentate and permeate side of the membrane. Whilst the tolerance limit of the membrane may be a determinative of the operable transmembrane pressure differential, it is conventional herein to apply a transmembrane pressure differential of from about 50 to about 500 kPa. Exemplary transmembrane pressure differentials of from about 50 to about 400 kPa, about 50 to about 300 kPa or about 100 to about 300 kPa may be mentioned.
(94) The transmembrane pressure differential may be controlled by inter alia: pressurizing the feed stream of the aqueous medium with a gas; adjusting the column height of the feed stream of the aqueous medium above the membrane; through the use of pumps to adjust the flow rate of the fluids on the retentate side of the membrane; through controlling drainage on the permeate side of the membrane; and/or, through the use of suction applied to the permeate side of the membrane.
(95) The transmembrane pressure differential may be maintained at a constant value within the aforementioned ranges during the contacting step. In the alternative, the transmembrane pressure differential may be moderated to provide a constant permeate flow rate: typically in this circumstance, the transmembrane pressure differential will increase during an contacting step or cycle and should, of course, be monitored to ensure that the pressure tolerance limit of the membrane is not exceeded.
(96) The particulate crystalline nanocomposite comprises a hexagonal lanthanum hydroxide (La(OH).sub.3) crystalline phase; a lanthanum oxide (La.sub.2O.sub.3) crystalline phase; a monoclinic calcium silicate (CaSiO.sub.3) crystalline phase; and, graphitic carbon nitride (g-C.sub.3N.sub.4) crystalline phase. In some embodiments, La(OH).sub.3 has a hexagonal crystalline phase. In some embodiments, La.sub.2O.sub.3 may exist in hexagonal, monoclinic, and/or cubic crystalline phases. In some embodiments, CaSiO.sub.3 has a monoclinic crystalline phase. It is not precluded that CaSiO.sub.3 may additionally exist in other crystalline phases, including triclinic and orthorhombic crystalline phases. In some embodiments, g-C.sub.3N.sub.4 has a cubic crystalline phase. At least a fraction of g-C.sub.3N.sub.4 is in the form of mesoporous nanosheets.
(97) In some embodiments, at least about 50 wt. %, for example at least about 60 wt. %, at least about 70 wt. %, or at least about 80 wt. % of the g-C.sub.3N.sub.4 is in the form of mesoporous nanosheets. As used herein, the term mesoporous nanosheets refers to the ultrathin, two-dimensional materials that possess mesopores with diameters of from about 2 to about 50 nm and are distributed across their surface or within their layers. In preferred embodiments, at least about 80 wt. % of the g-C.sub.3N.sub.4 is in the form of mesoporous nanosheets.
(98) In some embodiments, the ratio by weight of CaSiO.sub.3 to g-C.sub.3N.sub.4 to the sum of La(OH).sub.3 and La.sub.2O.sub.3 in the particulate crystalline nanocomposite is about (0.80-1.20):(0.80-1.20):(0.80-1.20), for example about (0.85-1.15):(0.85-1.15):(0.85-1.15), about (0.90-1.10):(0.90-1.10):(0.90-1.10), or about (0.95-1.05):(0.95-1.05):(0.95-1.05). In a preferred embodiment, the ratio by weight of CaSiO.sub.3 to g-C.sub.3N.sub.4 to the sum of La(OH).sub.3 and La.sub.2O.sub.3 in the particulate crystalline nanocomposite is about 1:1:1.
(99) The metal oxide nanoparticles include nanocomposite may exist in various morphological shapes, such as nanotubes, nanowires, nanoribbons, nanoblocks, nanobarrels, nanowhiskers, and mixtures thereof. In a preferred embodiment, the particulate crystalline nanocomposite includes acicular particles of La(OH).sub.3, La.sub.2O.sub.3, and CaSiO.sub.3. As used herein, acicular particles refer to needle-like structures characterized by their elongated, slender form and high aspect ratio (ratio of length to width), resembling thin, sharp needles. In certain embodiment, the acicular particles are disposed on g-C.sub.3N.sub.4 nanosheets and have an aspect ratio of at least about 3:1, for example at least about 4:1, at least about 5:1, at least about 6:1, at least about 7:1, at least about 8:1, at least about 9:1, or at least about 10:1.
(100) In some embodiments, the particulate crystalline nanocomposite includes acicular particles of La(OH).sub.3, La.sub.2O.sub.3, and CaSiO.sub.3 with a median length of from about 40 to about 100 nm, for example from about 45 to about 95 nm, from about 50 to about 90 nm, from about 55 to about 85 nm, of from about 60 to about 80 nm, as determined by transmission electron microscopy. In a preferred embodiment, the particulate crystalline nanocomposite includes acicular particles of La(OH).sub.3, La.sub.2O.sub.3, and CaSiO.sub.3 having a median length of about 77.8 nm.
(101) In some embodiments, the particulate crystalline nanocomposite includes aggregates of the mesoporous nanosheets of g-C.sub.3N.sub.4 with nanoparticles of La(OH).sub.3, La.sub.2O.sub.3, and CaSiO.sub.3. A two-dimensional porous structure is formed using curled and wrinkled nanosheets and platelets of g-C.sub.3N.sub.4, which enhance surface area and prevent stacking. The surface is decorated with well-dispersed needle-like metal oxide nanoparticles, along with a few aggregates, indicating successful integration of metal oxides onto the g-C.sub.3N.sub.4 matrix.
(102) In some embodiments, the particulate crystalline nanocomposite has a surface area of from about 60 to about 100 square meter per gram (m.sup.2/g), for example from about 62 to about 98 m.sup.2/g, from about 64 to about 96 m.sup.2/g, from about 66 to 94 m.sup.2/g, from about 68 to about 92 m.sup.2/g, from about 70 to about 90 m.sup.2/g, from about 72 to about 88 m.sup.2/g, from about 74 to about 86 m.sup.2/g, or from about 76 to about 84 m.sup.2/g, as determined by BET analysis.
(103) In some embodiments, the particulate crystalline nanocomposite has a surface area of from about 70 to about 90 m.sup.2/g, from about 71 to about 89 m.sup.2/g, from about 72 to about 88 m.sup.2/g, from about 73 to about 87 m.sup.2/g, from about 74 to about 86 m.sup.2/g, from about 75 to about 85 m.sup.2/g, from about 76 to about 84 m.sup.2/g, or from about 77 to about 83 m.sup.2/g, as determined by BET analysis. In a preferred embodiment, the surface area of the particulate crystalline nanocomposite determined by BET analysis is about 82.3 m.sup.2/g.
(104) In some embodiments, the particulate crystalline nanocomposite has an average pore diameter of from about 10 to about 25 nm, for example from about 11 to about 24 nm, from about 12 to about 23 nm, or from about 13 to about 22 nm, as determined by BJH desorption analysis. In a preferred embodiment, the particulate crystalline nanocomposite has an average pore diameter of about 14.27 nm.
(105) In some embodiments, the particulate crystalline nanocomposite has a pore volume of from about 0.1 to about 0.4 cm.sup.3/g, for example from about 0.12 to about 0.38 cm.sup.3/g, from about 0.14 to about 0.36 cm.sup.3/g, from about 0.16 to about 0.34 cm.sup.3/g, from about 0.18 to about 0.32 cm.sup.3/g, or from about 0.20 to about 0.30 cm.sup.3/g, as determined by BJH desorption analysis.
(106) In some embodiments, the particulate crystalline nanocomposite has a pore volume of about 0.1 to about 0.3 cm.sup.3/g, for example from about 0.11 to about 0.29 cm.sup.3/g, from about 0.12 to 0.28 cm.sup.3/g, from about 0.13 to about 0.27 cm.sup.3/g, from about 0.14 to about 0.26 cm.sup.3/g, from about 0.15 to about 0.25 cm.sup.3/g, from about 0.16 to about 0.24 cm.sup.3/g, or from about 0.17 to about 0.23 cm.sup.3/g, as determined by BJH desorption analysis. In a preferred embodiment, the particulate crystalline nanocomposite has a pore volume of about 0.220 cm.sup.3/g.
(107) In some embodiments, the particulate crystalline nanocomposite has a hysteresis loop of Type H3 (International Union of Pure and Applied Chemistry (IUPAC) classification), as determined by N.sub.2 adsorption-desorption analysis at 77 Kelvin (K). The H3 hysteresis loop is common in materials composed of plate-like particles, such as layered or sheet-like structures, and reflects the presence of slit-shaped mesopores without pore filling at high relative pressures.
(108)
(109) At step 52, the method 50 includes forming a solution of a calcium salt and an alkali metal silicate in a solvent including water and a C.sub.1-C.sub.4 alkanol. Exemplary calcium salts, which may be present alone or in combination, include but are not limited to calcium chloride, calcium sulfate, calcium carbonate, calcium phosphate, calcium acetate, calcium citrate, calcium lactate, calcium gluconate, calcium formate, calcium oxalate, calcium tartrate, calcium ascorbate, calcium benzoate, calcium propionate, calcium stearate, calcium hydroxide, calcium peroxide, calcium iodate, calcium molybdate, calcium hypochlorite, calcium thiocyanate, calcium chromate, calcium ferrite, calcium bromide, calcium fluoride, calcium sulfide, calcium arsenate, calcium tungstate, calcium borate, calcium perchlorate, and calcium hydride. In an embodiment, the calcium salt is selected from the group consisting of calcium sulfate (CaSO.sub.4), calcium nitrate (Ca(NO.sub.3).sub.2), calcium chloride (CaCl.sub.2)) and calcium acetate (Ca(CH.sub.3COO).sub.2). In a preferred embodiment, calcium salt is calcium nitrate.
(110) Exemplary alkali metal silicates, which may be present alone or in combination, include but are not limited to potassium silicate, lithium silicate, rubidium silicate, cesium silicate, sodium orthosilicate, potassium orthosilicate, lithium orthosilicate, rubidium orthosilicate, cesium orthosilicate, sodium disilicate, potassium disilicate, lithium disilicate, rubidium disilicate, cesium disilicate, sodium trisilicate, potassium trisilicate, lithium trisilicate, rubidium trisilicate, cesium trisilicate, sodium tetrasilicate, potassium tetrasilicate, lithium tetrasilicate, rubidium tetrasilicate, cesium tetrasilicate, sodium hexasilicate, potassium hexasilicate, lithium hexasilicate, rubidium hexasilicate, and cesium hexasilicate. In a preferred embodiment, alkali metal silicate is sodium metasilicate.
(111) In some embodiments, the molar ratio of the calcium salt to the alkali metal silicate is from about 1:5 to 5:1, for example about 1:4 to 4:1, about 3:1 to 1:3, about 1:2 to 2:1, or about 1:1.
(112) Exemplary C1-C4 alkanols, which may be present alone or in combination, include but are not limited to methanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, tert-butanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, methylpropanol, dimethylpropanol, ethylpropanol, cyclopropanol, fluoromethanol, chloromethanol, bromomethanol, and iodomethanol. In a preferred embodiment, the C1-C4 alkanol comprises or consists of ethanol.
(113) In an embodiment of step 52, the volume-by-volume (v/v) ratio of water to C1-C4 alkanol is in the range of about 1:5 to 5:1, for example about 1:4 to 4:1, about 1:3 to 3:1, or about 1:2 to 2:1. In a preferred embodiment, the v/v ratio of water to C1-C4 alkanol is 1:1.
(114) At step 54, the method 50 includes heating the solution at a temperature of from about 150 to about 250 C. to form a dry product of CaSiO.sub.3. This step involves the chemical reaction and dehydration process that are necessary for converting the precursor materials into the desired solid product. In some embodiments, heating takes place at temperature of from about 110 to about 210 C., for example from about 120 to about 220 C., from about 130 to about 230 C., from about 140 to about 220 C., from about 150 to about 210 C., from about 160 to about 200 C., from about 170 to about 190 C., or about 180 C. to form the dry product of CaSiO.sub.3. The solution is preferably heated in an autoclave; optionally, other known heating appliances may be used.
(115) At step 56, the method 50 includes forming graphitic-C.sub.3N.sub.4 by heating urea in a closed vessel at a temperature of from about 500 to about 700 C. Heating is done in a closed vessel at step 56 to maintain a controlled atmosphere, preventing the escape of volatile components and ensuring the formation of graphitic-C.sub.3N.sub.4 under the required conditions of pressure and temperature. In some embodiments, heating takes place at temperature of from about 500 to about 700 C., for example from about 525 to about 675 C., from about 550 to about 650 C., from about 575 to about 625 C., or about 600 C. Typically, heating is conducted for a period of from about 30 to 60 minutes, for example about 40 to about 50 minutes, or about 45 minutes. In an exemplary preferred embodiment, the urea is heated in a closed vessel to a temperature of about 600 C. for a period of about 45 minutes.
(116) At step 58, the method 50 comprises dispersing the CaSiO.sub.3, g-C.sub.3N.sub.4, and La.sub.2O.sub.3 in a polar protic solvent and heating the dispersion at a temperature of from about 150 to about 250 C. at a pressure of from about 2 to about 8 bar. In some embodiments, the CaSiO.sub.3, g-C.sub.3N.sub.4, and La.sub.2O.sub.3 are dispersed in a polar protic solvent and heating the dispersion at a temperature of from about 150 to 250 C., preferably 155 to 245 C., preferably 160 to 240 C., preferably 165 to 235 C., preferably 170 to 230 C., and preferably 175 to 225 C. at a pressure of from about 2.0 to 8.0 bar, preferably 2.5 to 7.5 bar, preferably 3.0 to 7.0 bar, preferably 3.5 to 6.5 bar, preferably 4.0 to 6.0 bar, and preferably 4.5 to 5.5 bar.
(117) Exemplary polar protic solvents include, but are not limited to, methanol, isopropanol, n-propanol, butanol, isobutanol, tert-butanol, pentanol, hexanol, cyclohexanol, ethylene glycol, propylene glycol, glycerol, formamide, mono(C.sub.1-C.sub.4)alkyl ethers of ethylene glycol, mono(C.sub.1-C.sub.4)alkyl ethers of propylene glycol dimethylformamide (DMF), acetic acid, propionic acid, lactic acid, formic acid, citric acid, phosphoric acid, trifluoroacetic acid, water, ammonia, methylamine, ethylamine, isopropylamine, n-propylamine, butylamine, sec-butylamine, tert-butylamine, diethylamine, dipropylamine, dimethylamine, triethylamine, triethanolamine, n-methylformamide (NMF), n-methylacetamide (NMA), hydrazine, hydroxylamine, and urea. In an exemplary embodiment, the polar protic solvent is a C.sub.1-C.sub.4 alkanol. In a preferred embodiment, the polar protic solvent is selected from the group consisting of mono(C.sub.1-C.sub.4)alkyl ethers of ethylene glycol. An exemplary polar protic solvent is ethylene glycol monomethyl ether.
(118) In some embodiments, the dispersion is heated: at a temperature of from about 150 to about 250 C.; and, at a pressure of from about 3 to 6 bar. In a preferred embodiment, the CaSiO.sub.3, g-C.sub.3N.sub.4, and La.sub.2O.sub.3 are dispersed in a polar protic solvent, and the dispersion is heated at a temperature of about 180 C. at a pressure of about 5 bar.
(119) Such heating of the dispersion may, in certain embodiments, be conducted for a duration of from about 3 to about 6 hours, for example from about 3.2 to about 5.8 hours, from about 3.4 to 5.6 hours, from about 3.6 to 5.4 about hours, or from about 3.8 to about 5.2 hours.
(120) At step 60, the method 50 includes separating the solid particulate crystalline nanocomposite from the heated dispersion. In some embodiments, separation may be done by centrifugation, decantation, sedimentation, dialysis, ultrafiltration, distillation, fractional distillation, steam distillation, vacuum distillation, crystallization, recrystallization, adsorption, absorption, chromatography, electrophoresis, membrane filtration, solvent extraction, sublimation, coagulation, and flotation. In a preferred embodiment, the solid particulate crystalline nanocomposite is separated from the heated dispersion by filtration.
(121) It is not precluded that the separated particulate crystalline nanocomposite is subjected to further processing. Such further processing may be performed in a single stage or multistage manner and may include one or more of: washing with water; drying; and, comminuting the nanocomposite in order to moderate particle morphology or the particle size distribution thereof. Exemplary drying conditions include a temperature of from about 50 to about 200 C., such as from about 100 to about 200 C. or from about 120 to about 180 C. Such drying may be carried out using known heating methods, such as a vacuum oven, rotary evaporator, microwave-assisted drying process, freeze-drying, and infrared drying.
EXAMPLES
(122) The following examples demonstrates a lanthanum hydroxide/calcium silicate @graphitic carbon nitride (La(OH).sub.3/CaSiO.sub.3@g-C.sub.3N.sub.4) nanocomposite material and method of preparation thereof. The examples are provided solely for illustration and are not to be construed as limitations of the present disclosure, as many variations thereof are possible without departing from the scope of the present disclosure.
Example 1: Fabricating the Calcium Silicate (CaSiO.SUB.3.)
(123) Equimolar amounts of calcium nitrate and sodium metasilicate were dispersed in 100 milliliters (mL) of ethanol:water (1:1 ratio by volume) in a 150 mL glass beaker and sonicated for 15 minutes (min). The mixture was then transferred to a 200 mL autoclave and placed in an oven operated at 180 degrees Celsius (C) for 2.0 hours (h). The product was further dispersed in 500 mL distilled water with an ultrasonic bath for 10 minutes, filtered via a Buchner system, rinsed with distilled water, and dried at 120 C. for 1.0 hour.
Example 2: Fabricating the Graphitic Carbon Nitride (g-C.SUB.3.N.SUB.4.)
(124) About 30.0 gram (g) of urea was placed in a 100 mL porcelain crucible and closed with its porcelain cover. The whole crucible and cover were wrapped with three layers of aluminum foil to reduce the urea loss of evaporation. The crucible was then heated via a furnace set at 600 C. for 1.0 hour.
Example 3: Fabricating the Lanthanum Hydroxide La(OH).SUB.3./La.SUB.2.O.SUB.3./CaSiO.SUB.3.@g-C.SUB.3.N.SUB.4
(125) An equal amount by weight of CaSiO.sub.3, g-C.sub.3N.sub.4, and lanthanum oxide (La.sub.2O.sub.3) was transferred to a mono wave-200 vial (G30) and dispersed in 20 mL ethylene glycol monomethyl ether via an ultrasonic bath for 30 minutes. The vial was then closed with its Teflon cover and placed in the Anton-Baar Monowave-200 operated at 180 C. and 5.0 bar pressure for one hour. The product formed was then dispersed in 1 liter (L) of distilled water with an ultrasonic bath for 30 minutes, filtered via a Buchner system, rinsed with distilled water, and dried at 150 C. for 2.0 hours.
(126) The crystallinity of, and phases present in the La(OH).sub.3/La.sub.2O.sub.3/CaSiO.sub.3@g-C.sub.3N.sub.4 nanocomposite were analyzed by X-ray diffraction (XRD), and the results are given in
(127) Transmission electron microscopy (TEM) images of the nanocomposite are depicted in
(128) The specific surface area of the prepared nanocomposite was determined using Brunauer-Emmett-Teller (BET) analysis.
(129) Adsorption
(130) For adsorption studies, 0.05 g of sorbent was measured in a separate 150 ml beaker. 100 mL of the 100 mg L.sup.1 BF solution was poured into each beaker. A portion of the mixture was withdrawn till the BF sorption reached the equilibrium. The aliquots were filtered via a 0.22 micrometer (m) syringe filter, and the absorbance was measured utilizing a UV-Vis-spectrophotometer (=550 nm).
(131) The contact time study of BF and sorption onto the as-prepared nanocomposite was studied. The BF and absorbance measured during the study were employed for calculating their remaining concentrations (unadsorbed) at each time interval Eq. 1. And Eq. 2 was used to calculate the adsorption capacity at each period (the BF or milligrams adsorbed onto one gram of sorbent, q.sub.t, mg g.sup.1).
(132)
wherein: Co the initial concentration; Ct concentration at time, t; V is the Volume of solution used; and, m is the mass of adsorbent.
(133)
(134) Adsorption Rate Order
(135) The adsorption rate order of BF removal by the prepared nanocomposite was studied via pseudo-first order (PF, Eq. 3) and pseudo-second order (PS, Eq. 4) kinetic models.
ln(q.sub.eq.sub.t)=ln q.sub.ek.sub.1.Math.t(3)
(136)
(137) The symbol q.sub.e (mg/g) represents the equilibrium adsorption capacity. The PF and PS constants are also time-dependent, with the former represented as k.sub.1 (min.sup.1) and k.sub.2 (g mg.sup.1 min.sup.1). The PF plot of the BF adsorption onto the nanocomposite is depicted in
(138) Adsorption Control Mechanism
(139) The rate-control mechanism of BF removal by the nanocomposite was studied using the intraparticle (IPD, Eq. 5) and the liquid-film (LFD, Eq. 6) diffusion model.
(140)
ln(1F)=K.sub.LF*t(6)
(141) The IPD constant is denoted by K.sub.IPD (mg g.sup.1 min.sup.1/2), and the LFD constant is designated by K.sub.LED (min.sup.1). C.sub.i: the boundary layer factor, expressed as mg g.sup.1.
(142) The LFD plot of the BF adsorption onto the nanocomposite was depicted in
(143) Numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described here.