WO2013052326A1

WO2013052326A1 - Methods for treating metals and metalloids

Info

Publication number: WO2013052326A1
Application number: PCT/US2012/057216
Authority: WO
Inventors: Roderick ABINET; Stephen Hurd; Vaishalibahen PATEL; Lucas Moore; Anna CASASUS; Jean Robert DURAND; Laura Sanders
Original assignee: Kemira Oy J
Priority date: 2011-10-04
Filing date: 2012-09-26
Publication date: 2013-04-11

Abstract

Methods of treating a material (e.g., a sample, which can include an entire batch or large quantity) having a contaminant, compositions, and the like, are provided. An exemplary embodiment of the present disclosure may be advantageous since the method can be efficient and can reduce capital costs that may be associated with currently used techniques.

Description

METHODS FOR TREATING METALS AND METALLOIDS

CROSS-REFERENCE TO RELATED APPLICATION

[0001 ] This application claims priority to U .S. provisional application entitled

"METHODS FOR TREATING METALS AND METALLOIDS," having serial number 61 /543, 1 56, fi led on October 4, 201 1 , which is entirely incorporated herein by reference.

BACKGROUND

[0002] The present embod iment(s) relate(s) to compositions and methods of treating contam inants, such as metals and metalloids.

[0003] One of the major problems facing industries such as municipal and industrial water, m ining, and energy industries is removal of contam inants (e.g., selenium, mercury, and the like) from waste generated by these industries. Federal, state, and local, standards for the maximum level of pol lutants are becoming more stringent.

SUMMARY

[0004] In view of the foregoing, one or more embodiments include a method of removing a contaminant from a material.

[0005] At least one embodiment provides a method of treating a material having one or more types of contaminants selected from a metal or a metal loid, where the method includes a) introducing a functional agent to the material, b) introducing a coagulant to the sample, and c) introducing a flocculant to the material. In an embodiment, the functional agent can include an alkali sulfide, a functional polymer having a nucleophilic functional group, or a combination thereof.

[0006] At least one embodiment provides for a composition including: an alkali sulfide compound, and a transport agent.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0007] Before the embodiments of the present disclosure are described in detail, it is to be understood that, unless otherwise indicated, the present disclosure is not lim ited to particular materials, reagents, reaction materials, manufacturing processes, or the like, as such can vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only, and is not intended to be lim iting. It is also possible in the present disclosure that steps can be executed in different sequence where this is logical ly possible. [0008] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit (unless the context clearly dictates otherwise), between the upper and lower limit of that range, and any other stated or intervening value in that stated range, is encompassed within the disclosure. The upper and lower limits of these smal ler ranges may independently be included in the smaller ranges and are also

encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included l imits are also included in the d isclosure.

[0009] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described.

[001 0] Al l publ ications and patents cited in this specification are herein incorporated by reference as if each individual publ ication or patent were specifically and individual ly indicated to be incorporated by reference and are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The citation of any publication is for its disclosure prior to the fi l ing date and should not be construed as an admission that the present disclosure is not entitled to antedate such publication by virtue of prior disclosure. Further, the dates of publication provided could be different from the actual publication dates that may need to be independently confirmed.

[001 1 ] As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be read ily separated from or combined with the features of any of the other several embod iments without departing from the scope or spirit of the present disclosure. Any recited method can be carried out in the order of events recited or in any other order that is logically possible.

[001 2] Embodiments of the present d isclosure will employ, unless otherwise indicated, techniques of chemistry, metallo-organic chemistry, and the like, which are within the skill of the art. Such techniques are explained fully in the literature.

[001 3] The examples are put forth so as to provide those of ordinary skil l in the art with a complete disclosure and description of how to perform the methods and use the compositions and compounds disclosed and claimed herein. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in °C, and pressure is at or near atmospheric. Standard temperature and pressure are defined as 20 °C and 1 atmosphere.

[0014] It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly d ictates otherwise. Thus, for example, reference to "a support" includes a plurality of supports. In this specification and in the claims that follow, reference will be made to a number of terms and phrases that shal l be defined to have the fol lowing meanings unless a contrary intention is apparent.

Discussion

[001 5] In various exemplary embodiments described herein, methods of treating a material (e.g., a sample, which can include an entire batch or large quantity) having a contaminant, a composition, and the like, are provided. An exemplary embodiment of the present disclosure may be advantageous since the method can be efficient and can reduce capital costs that may be associated with currently used techniques.

[001 6] In an exemplary embodiment, the method of treating a material having a contam inant (e.g., a metal or metalloid) includes, for example, treating the material with a functional agent, a coagu lant, and a flocculant, to produce a sol id material contain ing the contaminant. In add ition, the method can optionally include removing the solid material from the material.

[001 7] In an exemplary embodiment, the material may include one or more types of contaminants and these may include one or more types of metals, one or more types of metal loids, or a combination thereof (e.g., types of metals and/or types of metalloids), where the metal and/or a metalloid can be included in an organic or inorganic compound or ionic compound (e.g., anionic compound).

[00 1 8] In an exemplary embodiment, the material can be from or derived from: a m ine, an industrial or mun icipal water treatment center, an oil processing or refining center, a coal processing center or plant, a smelting center, a disposal or incineration center, a non- ferrous metal processing center, a sem iconductor fabrication center, mine water runoff (e.g., such as leachate from a tailings holding site, or mine dewatering), waste water stream from a coal-fired power plant, water from flue gas treatment, aqueous mixtures from one or more of any of the forgoing, and the like. In an embodiment, the material can be in the form of sludge, coal waste, coal ash, or the like, or a combination thereof, as wel l as aqueous mixtures of one or more of each of these.

[001 9] In an exemplary embodiment, the metal and metal loid can include selenium, lead, mercury, molybdenum, chromium, cadm ium, antimony, arsenic, manganese, cobalt, zinc, copper, and phosphorus. In an embodiment, the metal or metalloid can be in the form of an organic or inorganic or ionic compound or complex. In an embodiment, the metal or metal loid can be selected from one or more of the oxidative states of the metal or metal loid and can vary depending on the exact form of the organic or inorganic compound or ionic compound.

[0020] In an exemplary method, the material comprising a metal or metalloid contam inant may be treated with a functional agent. Although not intending to be bound by theory, the functional agent can function to change the oxidative state of the metal or metal loid so that the metal or metalloid is less soluble in the aqueous solution, or the functional agent may coordinate with the metal or metalloid. In an embodiment, the functional agent is selected from elemental sulfur, an alkal i sulfide, a functional polymer having a nucleophilic functional group, or a combination thereof.

[002 1 ] An exemplary alkali sulfide can include sod ium sulfide, lithium su lfide, and potassium sulfide. In an exemplary embodiment, the alkali sulfide is sodium sulfide.

[0022] An exemplary functional polymer comprises at least one functional monomer having at least one nucleophilic functional group. An exemplary nucleophilic functional group can include: a sulfur atom, a sulfur containing organic group, an amine group, a phosphine group, a hydroxyl group, a sulfide group, a thiol group, a mercaptan group, or a combination thereof. In an exemplary embodiment, the nuc leophilic functional group is sulfide. An exemplary functional monomer can includes al lyl methyl su lfide or di-al lyl sulfide.

[0023] I n an embodiment, the functional monomer may be polymerized with at least one additional monomer. The ratio of the functional monomer to the total monomer can be about 0.01 to 1 00% or about 10 to 50%. The functional polymer can have a molecular weight of about 1 000 to 1 ,000,000 Daltons.

[0024] An exemplary additional monomer that can be used to form the functional polymer can include: acrylic acid, vinyl sulfonic acid ,or vinyl sulfonate salts; vinyl phosphoric acid or vinyl phosphonate salts; vinylidene diphosphonic acid or salts thereof; methacrylic acid; vinyl acetate; vinyl alcohol; vinyl chloride; unsaturated mono- or di- carboxyl ic acids (e.g., maleic anhydride, maleic acid, itaconic acid) or anhydrides; vinyl chloride; styrene-p-su lfonic acid, or styrene sulfonate salts; acrylam ido-2- methylpropanesulfonic acid (AMPS); propargyl alcohol having formula HC≡C-CH₂-OH; butyr- 1 ,4-diol, or a copolymer thereof. An exemplary functional polymer can be a copolymer of al lyl methyl sulfide or acrylic acid.

[0025] In an exemplary embod iment, the functional agent may be combined with a transport agent. An exemplary transport agent is a cationic polyam ine. An exemplary cationic polyamine has a molecular weight of about 500 and 500,000 Daltons with a h igh charge density (e.g., 0.01 to 1 00 mole%, about 75 mole % or more, about 85 mole % or more, about 95 mole % or more, about 99 mole % or more, or 100 mole %). In an exemplary embodiment, the polyamine can be a copolymer of dimethylamine and epichlorohydrin. Another exemplary transport agent is an anion ic dispersant. An exemplary anionic dispersant is an anionic polyacrylate has a molecular weight of about 500 and 500,000 Daltons with a 0.01 to 1 00% charge density. Another exemplary transport agent is a nonionic dispersant. An exemplary nonionic dispersant has a molecular weight of about 500 and 500,000 Daltons. In an exemplary embodiment, a composition can include the functional agent and the transport agent, where each can be about 5 to 95% by weight of the composition.

[0026] According to an exemplary method, the material may be treated with a coagulant. Although not intending to be bound by theory, the coagulant can bind to the soluble metal or metal loid compounds in the material to form a colloid . The coagulant can be selected based on various treatment conditions, including, for example, the type(s) of metal or metal loid present in the material, the pH of the sample or the pH of the sample after treatment, and the l ike. In an embodiment, the coagulant may be a combination of coagulants, for example, added simultaneously or in different cycles of the method. An exemplary coagulant can be an iron salt, zero valent iron powder, an aluminum salt (e.g., aluminum chloride), alkali aluminate, or a combination thereof. An exemplary iron salt can include ferrous chloride, ferric chloride, ferric sulfate, ferrous sulfate, or a combination thereof. An exemplary aluminum salt can include polyaluminum chloride, alum inum chloride or alum inum su lfate. The alkali alum inate can include alum inate sodium, aluminate potassium, or lith ium alum inate.

[0027] According to an exemplary method, the material may be treated with a flocculant. Although not intending to be bound by theory, the flocculant can assist the colloid formed using the coagulant to come out of suspension and to form floes, which can be removed from the material (e.g., using a filter system). In an exemplary embodiment, the floccu lant can be an anionic polyacrylamide with a molecu lar weight of about 1 to 20 mi llion Daltons, varying in charge from about 5 to 50 mole%.

[0028] In an exemplary embodiment, the solid material in the treated material can be removed from the material using a system such as a filtering system (e.g., membrane filter (e.g., microfiltration), sieve fi lter, screen filter, ion-exchange fi lter, osmosis or reverse osmosis filtering, and the l ike) or other mechanism so that the material has a reduced amount of the contam inant. In another embodiment, the solid material can be removed using a gravity settler or a clarifier. In another embodiment, the material can be exposed to a system, such as those described above, to remove solids prior to treatment of the material .

[0029] In an exemplary embodiment, the steps can be performed in sequence as fol lows: introducing a functional agent to the material, introducing a coagulant to the material, and then introducing a flocculant to the material. According to the various embodiments, one or more of the steps may be repeated, as necessary or desired, for example, so as to remove a predetermined amount of contaminant from the material . In an exemplary embodiment, the first two steps of introducing the functional agent and the coagulant can be cycled two or more times prior to introduction of the flocculant to the material. In an exemplary embodiment, the introduction of the functional agent, the coagulant, and the flocculant to the material, can be cycled two or more times prior to removing the solid material. In an exemplary embodiment, the introduction of the functional agent, the coagulant, the flocculant to the material, and removal of the solid material, can be cycled two or more times to reach the desired level of the contaminant in the material.

[0030] According to the various embodiments, the steps of the method can be varied or modified, as necessary or desired, to accommodate various process cond itions such as, for example, the type of material, the type(s) of contaminant in the material, the amount of contam inant present in the material, the pH of the material, and the like.

[003 1 ] In an embodiment, the exemplary method may be used to remove selenium from a material. The selenium may be in the form of selenite and/or selenate. According to the exemplary method, the material containing selenium may be treated with a functional agent, and treated with a coagulant, and treated with a flocculant. The coagulation step may vary depending on the form of the selenium in the material. For example, if the predominant form of the selenium is selenite, the coagulant may include ferric chloride, ferrous chloride, or sodium al uminate. If the predominant form of the selenium is selenate, a reduction of the selenate may be useful to reduce the selenite to the less soluble selen ite, and the coagulant can include zero valent iron or alternatively ferrous chloride. If the pH of the material after treatment is of concern, then sodium aluminate may be used as the coagulant. Where the coagulant is ferrous chloride, the ferrous chloride may bind to residual dissolved sulfide in the treated material. After the coagulant has been added, the flocculant may be introduced to the material and causes the colloids (e.g., the solid material including the selenium) including the selenium to come out of suspension. Subsequently, the sol id material includ ing the selenium can be removed from the material, such as by using a fi ltering system.

EXAMPLES

[0032] Now having described the embodiments, in general, the examples describe some add itional embodiments. While embodiments are described in connection with the examples, there is no intent to l imit embodiments of the disclosure to these descriptions. On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of exemplary embodiments.

[0033] Example 1 : Exemplary Functional Polymer

[0034] An exemplary functional polymer was generated by the copolymerization of acrylic acid with ally 1 methyl sulfide. Water was added to a reactor (e.g., 1 77 g) and heated to about 90 °C. The acrylic acid (e.g., 281 g) and al ly 1 methyl sulfide (e.g., 25 g) were combined in a separate reactor and allowed to agitate to maintain homogeneity. This monomer mixture was fed into the heated reactor over the course of about 3 hours. At the same time of th is feed an initiator solution was prepared by adding sod ium persulfate (e.g.,

6.5 g) to water (e.g., 62 g), which was also fed over the course of the same 3 hours. A 40% solution of sodium bisulfite (e.g., 75 g) was also fed over the same 3 hour feed. After the completion of the feeds, water was added to each feed tank to rinse the tank and lines (e.g.,

5.6 g per line). The reactor was then allowed to cure for 1 hour, while maintaining the temperature and agitation. At this time the reactor was allowed to cool to about 50° C. The pH of the solution was adjusted using NaOH. The solids were adjusted to 40% active solids with water. The amounts noted above can be scaled up or down as needed for a particular appl ication.

[0035] Example 2 : Exemplary water treatment procedure

[0036] In the examples described herein, water or contaminated samples were treated in accordance with the procedure that follows. It should be noted that the exemplary water treatment steps below can be scaled up to accommodate larger volumes and also modified so that the process can be continuous. Also the water sample can be replaced with any other sample materials described herein.

[0037] Step 1 ) Allow water sample to reach room temperature by submerging sample bottle in a water bath or placing on a heated stir plate.

[0038] Step 2) Pour 250 mL to 1 L of water onto a glass beaker (500 mL to 1 L capacity).

[0039] Step 3) Add a magnetic stir bar to the beaker and begin stirring on a magnetic stir plate (450 RPM), or using overhead paddle agitators.

[0040] Step 4) Using an adjustable 1 - 1 0 mL pipette with plastic disposable tip to add a predetermined amount of functional agent to the water/sample.

[0041 ] Step 5) Stir for ten minutes. While stirring, measure water pH using calibrated pH meter and probe. If desired, adjust the pH to between 5 and 6 using dilute HCl (0.1 to 1 N). The pH may also be adjusted during step 6.

[0042] Step 6) After 10 minutes, add predetermined amount of coagulant to the water/sample with plastic disposable tip.

[0043] Step 7) Stir for two minutes.

[0044] Step 8) Using a plastic syringe (0 - 1 mL, 0 - 2 mL, or 0 - 10 mL capacity), add predetermined amount of flocculant to the water/sample.

[0045] Step 9) Stir for one minute.

[0046] Step 10) Remove beaker from stir plate and allow it to settle for at least five minutes.

[0047] Step 1 1 ) Filter beaker contents using vacuum filtration or syringe filtration with

0.1 to 0.45-micron filters.

[0048] Step 12) Collect filtrate in polyethylene bottles for analysis using EPA Method

200.8 ( 1994). Samples may be preserved with concentrated (-70%) nitric acid (up to 1 mL per 100 mL of sample). Save solids if desired for toxicity characteristic leaching procedure (TCLP) analysis.

[0049] Example 3 : Selenium removal Examples

[0050] An aqueous sample from coal fired power plant was obtained and treated in manner as described in Example 2, using three different treatment methods, as described below. [005 1 ] In Embodiment A, the functional agent used was sodium sulfide. The sodium su lfide was prepared by dissolving solid flakes of Na2S in deionized water to produce a solution of sodium sulfide ( 1 0,000 ppm). The a2S solution was added to the sample in a predeterm ined amount (500 ppm Na₂S weight/volume). In this embodiment, the coagulant was ferrous chloride solution (2800 ppm by volume) containing 13.8 ± 0.4% iron, and the flocculant (2 ppm) used was an anionic polyacrylamide having a molecular weight of about 12 to 1 5 m i l l ion Daltons. Using this method, the selenium level was reduced from 1 .008 ppm to 0. 1 34 ppm, which corresponds to a 86.8% reduction in the selenium level in the sample.

[0052] In Embodiment B, the functional agent used was the functional polymer of

Example 1 (4000 ppm as product volume/volume, the coagulant used was a ferric chloride solution (281 1 ppm as product volume/volume), and the flocculant (2 ppm) used was an anionic polyacrylamide having a molecular weight of about 12 to 1 5 million Daltons. The selenium level was reduced from 0.927 ppm to 0.267 ppm, which corresponds to a 71 % reduction in the selenium level in the sample.

[0053] In Embodiment C, the functional agent used was a sodium sulfide. The sodium sulfide was prepared by dissolving solid flakes of Na₂S in deionized water to produce a concentrated ( 1 0,000 ppm) solution of sodium sulfide. The sodium sulfide was combined with organ ic cationic polyam ine (50: 50) having a molecu lar weight of about 1 00,000 Daltons, and then di luted with deionized water (50% di lution). The diluted solution was added to the sample in a predetermined amount ( 1 5 ppm volume/volume). In this embodiment the coagulant used was ferric chloride solution (700 ppm as product volume/volume), and the flocculant (2 ppm) used was an anionic polyacrylamide having a molecu lar weight of about 12 to 1 5 m illion Daltons. The selenium level was reduced from 1 .3 ppm to 0.44 ppm, which corresponds to a 66% reduction in the selenium level in the sample.

[0054] In Embodiment D, the functional agent used was a sodium sulfide. The sodium sulfide was prepared by dissolving solid flakes of a2S in deionized water to produce a concentrated ( 10,000 ppm) solution of sodium sulfide. The sodium sulfide was combined with an organic anionic polyacrylate (50:50) having a molecular weight of about 100,000 Daltons, and then di luted with deionized water (50% dilution). The diluted solution was added to the sample in a predetermined amount ( 1 ppm volume/volume). In this embodiment the coagulant used was ferric chloride solution (700 ppm as product volume/volume), and the flocculant (2 ppm) used was an anionic polyacrylam ide having a molecular weight of about 12 to 1 5 m illion Daltons. [0055] In Embod iment E, the functional agent used was sodium sulfide. The sodium sulfide was prepared by dissolving solid flakes of Na^S in deionized water to produce a solution of sodium su lfide ( 1 0,000 ppm). The Na₂S solution was added to the sample in a predetermined amount (50 ppm Na2S weight/volume). In this embodiment, the coagu lant was ferrous chloride solution (52 ppm as product), and the flocculant (2.5 ppm) used was an anionic polyacrylamide having a molecular weight of about 1 2 to 1 5 m illion Daltons. Using this method, the selenium level was reduced from 0.697 ppm to 0.256 ppm, which corresponds to a 62% reduction in the selenium level in the sample.

[0056] It should be noted that ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to inc lude not only the numerical values expl icitly recited as the lim its of the range, but also to include al l the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a concentration range of "about 0.1 % to about 5%" shou ld be interpreted to include not only the explicitly recited concentration of about 0.1 wt% to about 5 wt%, but also include individual concentrations (e.g., 1 %, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5%, 1 . 1 %, 2.2%, 3.3%, and 4.4%) within the indicated range. In an embodiment, the term "about" can include traditional rounding according to the numerical value and the measurement techniques. In addition, the phrase "about 'x' to 'y'" includes "about 'x' to about 'y"\

[0057] It should be emphasized that the above-described embodiments are merely possible examples of implementations, and are merely set forth for a clear understanding of the principles of this d isclosure. Many variations and modifications may be made to the above-described embod iment(s) of the disclosure without departing substantial ly from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein with in the scope of this disclosure and protected by the fol lowing claims.

Claims

CLAIMS We claim at least the fol lowing:

1 . A method of treating a material having one or more types of contaminants selected from a metal or a metalloid, comprising:

a) introducing a functional agent to the material,

b) introducing a coagulant to the material, and

c) introducing a flocculant to the material.

2. The method of claim 1 , wherein the functional agent is selected from the group

consisting of: an alkali sulfide, a functional polymer having a nucleophil ic functional group, and a combination thereof.

3. The method of claim 2, wherein the functional polymer has at least one functional monomer comprising a nucleophilic functional group.

4. The method of claim 3, wherein the nucleophilic functional group includes one or more of: a elemental sulfur, a sulfur atom, a sulfur containing organic group, an am ine group, a phosphine group, a hydroxyl group, a su lfide group, a thiol group, a mercaptan group, and a combination thereof.

5. The method of claim 3, wherein the functional polymer has a molecular weight of about 1 000 to 1 ,000,000 Daltons.

6. The method of claim 3, wherein the functional polymer comprises a monomer

selected from the group consisting of: acrylic acid; vinyl sulfonic acid or vinyl sulfonate salts; vinyl phosphoric acid or vinyl phosphonate salts; vinylidene diphosphonic acid or salts thereof; methacrylic acid; vinyl acetate; vinyl alcohol ; vinyl chloride; unsaturated mono- or di- carboxyl ic acids or anhydrides; vinyl chloride; styrene-p-sulfon ic acid, or styrene sulfonate salts; acrylamido-2- methylpropanesu lfonic acid (AMPS); propargyl alcohol having formula HC≡C-CH₂- OH ; butyr- 1 ,4-diol, and a copolymer thereof.

7. The method of claim 1 , wherein the alkali sulfide is sodium sulfide.

8. The method of claim 1 , wherein the contaminant is selected from the group consisting of: selenium, lead, mercury, molybdenum, chromium, cadmium, antimony, arsenic, manganese, cobalt, zinc, copper, phosphorous, and a combination thereof.

9. The method of claim 1 , wherein the material is a selected from the group consisting of: sludge, coal waste, coal ash, an aqueous mixture of any one of these, and a combination thereof.

1 0. The method of claim 1 , wherein the coagulant is selected from the group consisting of: an iron salt, an aluminum salt, alkali aluminate, and a combination thereof.

1 1 . The method of claim 1 , wherein the coagulant is selected from the group consisting of: ferrous chloride, ferric chloride, and a combination thereof.

12. The method of claim 1 , wherein the flocculant is an anionic polyacrylamide.

1 3. The method of claim 1 , wherein the functional agent is provided in a transport media.

14. The method of claim 1 3, wherein the transport media is an organic cationic

polyamine.

1 5. The method of c laim 1 , further comprising:

d) removing a solid material from the material, wherein the sol id material includes the contaminant.

The method of claim 1 5, wherein removing includes using a system selected from the group consisting of: a settler, a clarifier, a fi ltering system, and a combination thereof.

The method of claim 1 , further comprising:

d) filtering the material to remove a solid material, wherein the solid material includes the contaminant.

1 8. The method of claim 1 , wherein steps a), b), and c) are performed in the sequential order of step a), step b), and then step c).

19. The method of claim 1 , wherein step a) and step b) are repeated two or more times prior to step c).

20. A composition comprising:

an alkali sulfide compound, and

a transport agent.

21 . The composition of claim 20, wherein the alkali sulfide is sodium sulfide.

22. The composition of claim 20, wherein the transport agent is selected from the group consisting of: an organic cationic polyamine, an organic anionic polyacrylate, and a combination thereof.