HK1072071B - Compositions for removing metal ions from aqueous process solutions and methods of use thereof - Google Patents

Description

Compositions for removing metal ions from aqueous process solutions and methods of use thereof

Cross reference to related applications:

the patent application of the invention is given priority over provisional patent application numbers 60/309,836, 60/309,837 and 60/309,854, which are handed over at 8/3/2001; all of which are incorporated herein by reference in their entirety.

Technical Field

A composition and method of using such composition to remove metal ions from an aqueous process solution is described.

Background

Various metals are used in many industrial processes. For example, silver is used in many imaging industry processes such as photography, thermography, photothermographic, and the like. However, such processes result in waste solutions containing metal ions at concentrations that are environmentally unacceptable. In addition, many countries now have legislation enacted to control the concentration of some metal ions emitted to the environment. Because it can be costly to process large volumes of untreated waste solution on an industrial scale, there has been a concerted effort to treat waste solutions in a cost effective manner. Further, these metals may prove sufficiently valuable for their recovery.

Methods such as ion exchange, electrolysis and deposition have been utilized to remove metals from aqueous waste solutions. However, these known methods all have their limitations. Ion exchange processes are expensive, slow and impractical. Ion exchange resins are expensive because they require complex and elaborate manufacturing processes. Some of these costs can be compensated for by regenerating the ion exchange resin. However, the waste solution produced during regeneration must generally also be disposed of. Similarly, electrolysis is expensive due to maintenance costs, the power supply and energy input required, etc. Electrolysis is also sensitive to contaminants and generally provides insufficient concentrations for metal recovery.

Settling processes typically use one or more reagents to transfer the metal to a material that is no longer soluble in the system and settles to the bottom of the reaction tank. However, the popular known settling processes have limitations such as the possibility of forming undesirably large amounts of non-renewable sludge. Some settling processes require heating to very high temperatures, for example above 80 ℃, to provide useful results. Still other settling methods require the use of a varying pH in order to convert the metal into an insoluble material.

Accordingly, there remains a need for a method for efficiently recovering metal ions from aqueous waste solutions (hereinafter referred to as aqueous process solutions).

Summary of The Invention

The present invention is directed to a method for effectively removing metal ions from an aqueous process solution.

Such a method comprises: (i) reacting metal ions in an aqueous process solution containing a wetting agent with a treatment composition containing a non-metallic compound to form an organometallic complex precipitate, and (ii) separating the organometallic complex precipitate from the aqueous process solution. The step of carrying out the reaction is preferably carried out at a temperature of less than or equal to about 50 ℃. The process is preferably carried out at a pH of greater than or equal to about 3.0. In a particular embodiment, the non-metallic compound included in the treatment composition is a thiuram. In another embodiment, the treatment composition further comprises an additional non-metallic compound that is a dithiocarbamate.

The present invention is also directed to the products obtained by the above process.

Detailed Description

The present invention provides a method for removing metal ions from an aqueous process solution. The term "aqueous process solution," as used herein, means any liquid containing a concentration of metal ions in the range of about 1ppm to about 15,000 ppm. The term "about" as used herein means plus or minus 10% of the referenced value. The term "aqueous solution" as used herein means containing more than about 50% water or water-miscible solvent by weight of the solution. The methods used herein for aqueous process solutions can also be used for suitable gaseous process mixtures. Non-limiting examples of aqueous process solutions include process solutions obtained by the following techniques: photography, photothermographic, thermographic, lithographic, metallurgical, semiconductor polishing, and X-ray imaging, among others. The term "metal ion" as used herein means a soluble form of any metal in groups I B to VIIB and VIII of the periodic Table (according to the handbook of CRC chemistry and Physics, 62 nd edition, 1981-1982), including elements having atomic numbers 58-71 and 90-103 such as aluminum, gallium, indium, thallium, germanium, tin, lead, antimony, bismuth, mixtures thereof and alloys thereof. Metal ions of particular interest are those specified in the Resource Conservation Recovery Act (RCRA). These metal ions are preferably selected from the group consisting of arsenic, barium, cadmium, chromium, cesium, copper, iron, lead, mercury, nickel, selenium, silver, technetium, thallium, zinc, actinides, lanthanides, mixtures thereof and alloys thereof.

The present invention is directed to a method or process for reacting metal ions in an aqueous process solution containing a wetting agent with a treatment composition containing a non-metallic compound to form an organometallic complex precipitate and separating the organometallic complex precipitate from the aqueous process solution. Such organometallic complexes may be isolated by any technique or process known to those skilled in the art, for example by settling, filtration, centrifugation, and the like. The residual metal ion concentration in the treated aqueous process solution may be less than about 100ppm, preferably less than about 20ppm, more preferably less than about 5 ppm.

It has been surprisingly found that the process of the present invention can effectively remove metal ions to such low concentrations as described above, even in the presence of high concentrations of chelating agents. Chelating agents are typically used to maintain the concentration of metal ions in the process solution, thereby preventing the metal ions from being removed. The present invention can be used to effectively remove metal ions from process solutions in which the numerical ratio of chelating agent to metal ion can be greater than about 500: 1. In fact, the method of the invention can also be used effectively in any of the following cases: wherein the numerical ratio of chelating agent to metal ion is from about 1,250,000: 1 to about 10: 1; from about 500,000: 1 to about 20: 1; and from about 100,000: 1 to about 100: 1.

Such treatment compositions of the present invention comprise a suitable carrier in an amount of from about 1.0% to 100%, preferably from about 50% to 99.99%, by weight of the composition, of a non-metallic compound (which may be associated with a metal ion) and from about 0.0% to about 99%, preferably from about 0.01% to about 50%, by weight of the composition. Preferably, the non-metallic compound is not a polymer. The treatment composition may be provided in dry or liquid form. The carrier may thus be any liquid or solid material known to those skilled in the art which is either neutral in effect or which enhances one or more properties of the non-metallic compound and its use, for example enhancing its storage and handling properties. One example of a suitable carrier is mineral oil.

In one embodiment of the present invention, the non-metallic compound included in the treatment composition of the present invention is a thiuram, which may also be referred to as tetramethylthiuram disulfide (trade name). Thiuram is only slightly soluble in aqueous process solutions. The term "slightly soluble" as used herein means that less than 0.1% by weight of the material is soluble in the aqueous process solution. Without wishing to be bound by any one theory, it is believed that the non-metallic compounds of the present invention are capable of forming an organometallic complex with a metal ion. This organometallic complex becomes a precipitate which can be separated from the aqueous solution by separation techniques or methods known to those skilled in the art. Non-limiting separation techniques or methods include filtration, gravity settling, centrifugation, flocculation, cake filtration, membrane filtration, and flotation (liquid/air filtration).

A group of thiurams is characterized by having the general formula (I) as illustrated below:

wherein m is an integer of 1 or 2; r₁、R₂、R₃And R₄Are individually selected from C₁-C₁₀Linear alkyl radical, C₃-C₁₀Alkyl with a forked chain, C₃-C₁₀Cycloalkyl groups and substituted and unsubstituted aryl groups. Image powerAs is well known to those skilled in the art, any carbon or hydrogen atom in each of the above R groups may be substituted with a chemical moiety that can modify the properties of the non-metallic compound without significantly affecting the desired solubility properties.

Examples of useful nonmetallic compounds of formula (I) include, but are not limited to, tetramethylthiuram monosulfide (CAS)^#97-74-5); bis (dimethyldithiocarbamoyl) disulfide (CAS)^#137-26-8); tetrabenzylthiuram disulfide (CAS)^#10591-85-2); tetraethylthiuram disulfide (CAS)^#97-77-8); tetrabutylthiuram disulfide (CAS)^#1634-02-2); dipentamethylenethiuram tetrasulfide (CAS)^#120-54-7) and mixtures thereof.

In another embodiment of the present invention, the treatment composition of the present invention further comprises a water soluble non-metallic compound which is a dithiocarbamate. One class of dithiocarbamates is characterized by the general formula (II) as illustrated below:

wherein n is an integer of 1 or 2; 0 is an integer of 1 or 2; r₅And R₆Are each selected from C₁-C₁₀Linear alkyl radical, C₃-C₁₀Alkyl with a forked chain, C₃-C₁₀Cycloalkyl groups and substituted and unsubstituted aryl groups; y is an element selected from groups IA and IIA of the periodic Table. As is well known to those skilled in the art, the carbon or hydrogen atoms in each of the above R groups may be substituted with other moieties to enhance the performance of such non-metallic compounds.

Examples of useful nonmetallic compounds having the formula (II) include, but are not limited to, sodium dimethyldithiocarbamate (CAS)^#128-04-1); diethyldithiocarbamate (CAS)^#148-18-5); dibenzyl disulfideSubstituted sodium Carbamate (CAS)^#55310-46-8); dibutyldithiocarbamate (CAS)^#136-30-1); and mixtures thereof.

The aqueous process solution also contains a wetting agent in a concentration of about 0.01 to 10 molar, more preferably about 0.025 to 0.5 molar, and most preferably about 0.05 to 0.25 molar. Some process solutions may already contain wetting agents as a component of the waste stream. For example, photographic waste solutions typically contain a sufficient concentration of wetting agent. If the wetting agent is not present in the aqueous process solution, an appropriate amount of wetting agent should be added. Wetting agents, also known as surfactants, are compounds that lower the surface tension of a liquid, or reduce the interfacial tension between two liquids or a liquid and a solid. Thus, it is believed that the wetting agent can help lower the barrier to the reaction. The wetting agent may be dissolved in both organic and aqueous solutions. However, it is preferred that the wetting agent used here is at least soluble in aqueous solution at the concentrations used. General classes of useful wetting agents include, but are not limited to, nonionic surfactants, anionic surfactants, cationic surfactants, carboxylic acids, alcohols, and amines. Zwitterionic and amphoteric surfactants may also be useful. Examples of useful wetting agents are disclosed in encyclopedia of Chemical technology (John Wiley & Sons, New York, published), U.S. Pat. No.6,399,676 to Labude et al at 6/4/2002 and U.S. Pat. No.6,087,312 to Masotti et al at 7/11/2000, all of which are incorporated herein by reference in their entirety. Examples of useful wetting agents include, but are not limited to, acetic acid, propionic acid, methanol, ethanol, propanol, tetraethylammonium hydroxide, fatty acids and salts thereof, alkyl aryl sulfonates, and mixtures thereof.

The process of the invention can be carried out under a wide range of reaction variables which can be modified and optimised according to any particular process. As in any chemical reaction, increasing the reaction residence time, i.e., extending the physical contact of the aqueous process solution of the nonmetallic compound, is beneficial for increasing the amount and/or size of the precipitated organometallic complex. Accordingly, the reaction or residence time should be extended to the greatest extent possible, provided that other process and economic variables are taken into account in combination. Typically, the reaction or residence time is at least 0.1 hour, preferably from about 0.5 hours to about 125 hours, more preferably from about 1 hour to about 10 hours. As is well understood by those skilled in the art, reduced reaction or residence times may be required at higher reaction temperatures.

The reaction can be carried out under a wide range of temperature conditions. Preferably, the reaction is carried out at a temperature of less than or equal to about 50 deg.C, more preferably less than or equal to about 45 deg.C, and most preferably at room temperature. Room temperature, as used herein, means the normal temperature of the surrounding environment, typically in the range of about 5 ℃ to about 40 ℃. Thus, the process of the present invention can be carried out without or with little heating, thereby reducing the cost of heat input to the system. However, for optimum process results, slight heating to bring the system within the above reaction temperature range is still required.

Because at least some of the non-metallic compounds in the treatment composition are sparingly soluble in the aqueous process solution, any known mixing technique is preferably used during the reaction and after the initial reaction. However, as is well known to those skilled in the art, if a small amount of hydrophobic component is present in a system where the hydrophilic component is predominant, the introduction of air through the system may result in the formation of an emulsion. Such emulsions will generally form a layer on top of the hydrophilic phase. This emulsion layer may be removed by any technique or method known in the art, such as by skimming techniques. If techniques such as skimming cannot be used for the separation step, the formation of an emulsion layer can be prevented by minimizing the amount of air introduced into the system after the treatment composition is added to the aqueous solution. For example, the formation of a vortex that can introduce air into the system can be prevented by placing a paddle outside the center of the tank bottom to control the mixing operation. Alternatively, the reaction tank may have a floating top which can meaningfully reduce the amount of air in the top of the mixture in the reaction tank.

Finally, the present invention can be practiced over a wide range of pH conditions, particularly if the process of the present invention is practiced in a substantially oxygen-free environment. However, due to the increased likelihood of degradation of organic materials by oxidized metal ions in an oxygen-rich environment (e.g., by Fenton's reaction), the process of the present invention is preferably carried out at a pH of greater than or equal to about 3.0, more preferably at a pH of about 4.0 to 12.0, and most preferably at a pH of about 7.0 to 12.0. It is also believed that the process of the present invention provides better separation of metal ions at lower surface tension conditions, for example, at the surface tension of a solution of 1% by weight acetic acid in water.

In one embodiment of the invention, the process comprises introducing the treatment composition of the invention into an aqueous process solution in a batch or continuous system. Such systems may be operated in parallel and/or in series. Such systems typically employ a vessel, such as a tank, which contains the aqueous process solution, and such a vessel is adapted to provide the mixing operation, e.g., any mixing technique known to those skilled in the art may be used. The treatment composition is added in a concentration ratio to the metal ions present in the aqueous process solution; any well known method of addition may be used, for example, by metering in. In such embodiments, the treatment composition is added at a concentration such that the molar ratio of the non-metallic compound to the metal ions present in the aqueous process solution is from about 1.0: 1.0 to about 1.0: 4.0, preferably from about 1.0: 1.2 to about 1.0: 3.0, more preferably from about 1.0: 1.5 to about 1.0: 2.5. Some non-metallic compounds even at concentrations of at least 2.5X 10, based on the total weight of the aqueous process solution and the non-metallic compound^-3% is still effective. More non-metallic compounds may be required at lower pH, e.g., pH values below about 4, in oxygen-rich environments, and when higher concentrations of contaminants are present, e.g., greater than about 5 ppm. The contaminant may be any compound other than metal ions and water. Furthermore, if the aqueous process solution does not contain the desired wetting agent in the above-mentioned concentrationsThen the appropriate amount of wetting agent should be added.

This embodiment also includes a separation step after completion of the reaction, or after an appropriate reaction or residence time. Any separation technique or method known to those skilled in the art may be used to separate the organometallic complex precipitate from the aqueous process solution, for example, settling, centrifugation, filtration, and the like. In a continuous system, the separation apparatus may be arranged in series with the vessel in which the mixing takes place. The resulting precipitate is then further processed as described later.

In another embodiment of the invention, the aqueous process solution containing metal ions may be introduced into a bed of a treatment composition containing a non-metallic compound in the form of a powder or beads. If the process solution does not contain the desired concentration of wetting agent, an appropriate amount of wetting agent can be added. In this embodiment, the reaction bed is packed with the treatment composition, and the flow of aqueous process solution is controlled by gravity or positive pressure through the bed, with reaction or residence time being optimized for other process and economic variables, etc. The reaction bed may have any acceptable geometry. Typically, 2 moles of metal ions will require about 1 mole of the non-metal compound. More non-metallic compounds may be required at lower pH conditions, e.g., pH below about 4, or in an oxygen-rich environment, or when higher concentrations of contaminants are present, e.g., about 5ppm contaminant concentration. The treatment composition in the reaction bed should be replaced when the metal ion removal capacity has reached an unacceptable level. The resulting precipitate is further processed as described below.

Alternative ingredients known to those skilled in the art may also be used to assist or optimize any of the process steps described above. For example, flocculants may be used to aid the settling process. Non-limiting examples of flocculants include acrylates. Also, an anti-foaming agent may be used in the mixing step, provided that the degree of agitation is not changed. Non-limiting examples of anti-foaming agents include silicone oils.

As is well known to those skilled in the art, the method of the present invention may be used in conjunction with commonly known metal ion recovery systems including photochemical developers, fixatives, bleach-fixing processes utilizing metal displacement, electrolyte recovery, chemical precipitation, ion exchange and reverse osmosis. For example, the aqueous process solution may be subjected to an electrolytic treatment prior to use of the process of the invention. Alternatively, the process of the invention may be used first before the electrolytic treatment.

As mentioned above, it is believed that the non-metallic compounds of the present invention react with metal ions to form an organometallic complex. Without wishing to be bound by any one theory, it is believed that the metal ions associate with one or more sulfur groups on the non-metallic compound via van der waals forces, ionic forces, delta bonds, and/or sigma bonds. Thus, the recovered organometallic complex can be further processed by any method known to those skilled in the art to remove these attractive forces and thereby recover the metal ions as native metals. In addition, such complexed non-metallized matter may be simply removed by any method known to those skilled in the art. Examples of suitable removal techniques include, but are not limited to, oxidation, degradation, acidification, and flame refining.

Examples

Example 1

Use of treatment compositions by mixing

The aqueous process solution containing the metal ions may be introduced into a vessel equipped with a mixing device, and if the process solution does not contain the desired concentration of the above-mentioned wetting agent, the wetting agent may be added. The mixing device may be any device that can sufficiently agitate the liquid. Typical examples include, but are not limited to, mixers such as Lightin series 10, and pumps such as Iwaki MD-70 model March IA-MD. Once the liquid has been transferred into the container, the treatment composition can be added and the mixture stirred. The reaction is allowed to proceed until the desired metal ion concentration is reached. The reaction time required to complete is influenced by a number of factors, including temperature, pH and solution composition.

Specifically, silver ions may be removed from a photochemical fixer solution having a silver ion concentration of about 2000 ppm. The reaction may be carried out at a pH of about 7 and a reaction temperature of about 25 c as described below. A 55 gallon (208 liter) container was used, equipped with a side mounted mixer. The retort was allowed to mix thoroughly while minimizing the amount of air introduced into the system, and 50 gallons (189 liters) of photochemical fixer solution was added. The concentrations of the individual components in the fixer solution are not readily discernible because such fixer solutions are actually waste streams discharged from photographic laboratories. However, the fixer waste solution should contain about 0.01 to 0.1 mole of acetate, which is a wetting agent, as estimated from the starting composition used. After transfer to the mixer, 2 lbs (0.9 kg) of pure bis (dimethyldithiocarbamoyl) disulfide (CAS)^#137-26-8) are added in powder form. After allowing the reaction to proceed for about 4 hours, the reaction mixture was allowed to settle for 30 minutes to form a layer of precipitate containing the organometallic complex at the bottom of the vessel. The silver ion concentration was tested with an aqueous supernatant solution, which was measured with a flame atomic absorption photometer from Perkin-Elmer. The experimental procedure for obtaining metal ion concentrations using such atomic absorption photometers is well known in the art. The concentration of silver ions contained in the filtered water solution is less than 5 ppm.

Example 2

Use of treatment composition in a column

The treatment composition of the present invention may also be used in a fixed bed reactor, such as a column, by compressing the treatment composition into pellets or beads having a length or diameter of about 2 to about 6 millimeters, respectively, and then placing them in the fixed bed reactor. Using a column as an example, the column chamber may be tubular with suitable connectors at both ends to allow aqueous process solution to enter and exit the column while maintaining the pellet of treatment composition in the column in an intact state. Initially, if the concentration of wetting agent in the process solution does not reach the levels described above, an appropriate amount of wetting agent may be added. Once the treatment composition is added to the column, the aqueous process solution is slowly pumped into the column. The treated solution, after leaving the cartridge, can be filtered to produce a precipitate of the organometallic complex containing silver ions. This embodiment provides a treated solution having a concentration of silver ions of less than about 10ppm by adjusting the feed flow rate. The adjustment of the flow rate can compensate for other performance affecting factors such as initial silver ion concentration, pH, and other metal ions.

Specifically, silver ions may be removed from a photochemical fixer solution containing silver ions at a concentration of about 2000 ppm. The experiment was carried out at a pH of about 7 and a reaction temperature of about 25 ℃ as follows. A column large enough to hold about 10 pounds (4.5 kg) of pure bis (dimethyldithiocarbamoyl) disulfide (CAS) in pellet form is used^#137-26-8), about 200 gallons (757 liters) of the photochemical fixer solution was stably pumped into the column at a rate of one gallon (3.8 liters) per hour, thus, the experiment took about 200 hours to complete. The residence time was about 5 hours. The treated solution exiting the column was filtered through a 1 micron bag filter to produce a precipitate containing silver ions. Bag filters are commercially available from FilterSpecialist, Inc. The filtered aqueous solution was measured for silver ion concentration using a Perkin Elmer flame atomic absorption photometer. The experimental procedure for obtaining metal ion concentrations using such atomic absorption photometers is well known in the art. The filtered aqueous solution contains a silver ion concentration of less than about 10 ppm.

Claims (18)

1. A method for removing metal ions from an aqueous process solution comprising:

reacting metal ions in an aqueous process solution containing a wetting agent with a treatment composition containing a non-metallic compound including a thiuram, monomer to form an organometallic complex precipitate, wherein the reaction is carried out at a temperature less than or equal to 50 ℃; and separating the organometallic complex precipitate from the aqueous process solution.

2. The method of claim 1, wherein the reacting step is carried out at a pH of greater than or equal to about 3.

3. The method of claim 1, wherein the non-metallic compound is characterized by the general chemical formula (I)

Wherein m is an integer of 1 or 2; and is

R₁、R₂、R₃And R₄Are individually selected from C₁-C₁₀Linear alkyl radical, C₃-C₁₀Alkyl with a forked chain, C₃-C₁₀Cycloalkyl groups and substituted and unsubstituted aryl groups.

4. The method of claim 3, wherein the non-metallic compound is selected from the group consisting of tetramethylthiuram monosulfide, bis (dimethyldithiocarbamoyl) disulfide, tetrabenzylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, dipentamethylenethiuram tetrasulfide, and mixtures thereof.

5. The method of claim 1, wherein the treatment composition further comprises an additional non-metallic compound which is a dithiocarbamate.

6. The method of claim 5, wherein the additional non-metallic compound is characterized by the general chemical formula (II)

Wherein n is an integer of 1 or 2;

0 is an integer of 1 or 2;

R₅and R₆Are individually selected from C₁-C₁₀Linear alkyl radical, C₃-C₁₀Alkyl with a forked chain, C₃-C₁₀Cycloalkyl groups, and substituted and unsubstituted aryl groups; and

y is an element selected from groups IA and IIA of the periodic Table.

7. The method of claim 6, wherein the additional non-metallic compound is selected from the group consisting of sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, sodium dibenzyldithiocarbamate, sodium dibutyldithiocarbamate, and mixtures thereof.

8. The method of claim 1 or 5, wherein the metal ion is selected from the group consisting of arsenic, barium, cadmium, chromium, cesium, copper, iron, lead, mercury, nickel, selenium, silver, technetium, thallium, zinc, actinides, lanthanides, mixtures thereof, and alloys thereof.

9. The method of claim 1 or 5, wherein the non-metallic compound is present in a concentration of from about 1.0: 1.0 to about 1.0: 4.0 as calculated as a molar ratio of the non-metallic compound to the metal ion in the aqueous process solution.

10. A product obtained from a process comprising:

reacting metal ions in an aqueous process solution containing a wetting agent with a treatment composition containing a non-metallic compound including a thiuram, monomer to form an organometallic complex precipitate, wherein the reaction is carried out at a temperature of less than or equal to 50 ℃; and is

The organometallic complex precipitate is isolated from the aqueous process solution.

11. The product of claim 10 wherein the step of conducting is carried out at a pH of greater than or equal to about 3.0.

12. The product of claim 10 wherein the non-metallic compound is characterized by the following general formula (I):

wherein m is an integer having a value of 1 or 2; and is

R₁、R₂、R₃And R₄Are individually selected from C₁-C₁₀Linear alkyl radical, C₃-C₁₀Alkyl with a forked chain, C₃-C₁₀Cycloalkyl groups and substituted and unsubstituted aryl groups.

13. The product of claim 12 wherein the non-metallic compound is selected from the group consisting of tetramethylthiuram monosulfide, bis (dimethyldithiocarbamoyl) disulfide, tetrabenzylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, dipentamethylenethiuram tetrasulfide, and mixtures thereof.

14. The product of claim 10 wherein the treatment composition further comprises an additional non-metallic compound which is a dithiocarbamate.

15. The product of claim 14, wherein the additional non-metallic compound is characterized by the following general chemical formula (II):

wherein n is an integer of 1 or 2;

0 is an integer of 1 or 2;

R₅and R₆Are individually selected from C₁-C₁₀Linear alkyl radical, C₃-C₁₀Alkyl with a forked chain, C₃-C₁₀Cycloalkyl groups and substituted and unsubstituted aryl groups; and is

Y is an element selected from group IA and IIA of the periodic Table.

16. The product of claim 15 wherein the additional non-metallic compound is selected from the group consisting of sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, sodium dibenzyldithiocarbamate, sodium dibutyldithiocarbamate, and mixtures thereof.

17. The product of claim 10 or 14 wherein the metal ion is selected from the group consisting of arsenic, barium, cadmium, chromium, cesium, copper, iron, lead, mercury, nickel, selenium, silver, technetium, thallium, zinc, actinides, lanthanides, mixtures thereof, and alloys thereof.

18. The product of claim 10 or 14, wherein the non-metallic compound is present in a concentration of about 1.0: 1.0 to about 1.0: 4.0 as calculated as a molar ratio of the non-metallic compound to the metal ion in the aqueous process solution.