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Title:
METHOD FOR INCREASED CAPACITY OF ION EXCHANGE MEDIA
Document Type and Number:
WIPO Patent Application WO/2001/002076
Kind Code:
A1
Abstract:
A method of increasing anion ion exchange capacity by using certain multivalent acids or salts. Also, a method for modifying pH working range of weakly basic anion ion exchangers for the purpose of metal extraction or other ion exchange processes using multivalent inorganic or organic acids or salts or esters or oxides. Media can be altered or a new media developed that will have a substantially higher loading capacity, able to work at much higher pH range, easily able to remove metal, able to quickly regenerate, and does not have all the environmental liabilities of ion exchange media in use today.

Inventors:
Quigley Jr., Leroy B. (37 Libera Street, Cranston, RI, 02920, US)
Application Number:
PCT/US2000/017940
Publication Date:
January 11, 2001
Filing Date:
June 29, 2000
Export Citation:
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Assignee:
Quigley Jr., Leroy B. (37 Libera Street, Cranston, RI, 02920, US)
International Classes:
B01D15/04; B01J41/12; B01J43/00; (IPC1-7): B01D15/04; C08G59/16; C08G73/02; C08J7/14
Foreign References:
US4195138A1980-03-25
US5605563A1997-02-25
Download PDF:
Claims:
Claims: What is claimed is: 1. A method whereby polyvalent and hydroxy polyvalent acid, or salt of, or polymers of is applied to organic or inorganic amine functionality's by simple exposure and adsorption to form a modified amine functionality capable of increased capacity, increased selectivity, increased kinetics, modification of pKa either upward or downward, and ease of metal remova
1. l.
2. For adsorption and removal of mono or divalent metal anions, and/or cation and/or complexes thereof.
3. A method of construction of a new or ability to change certain existing ion exchange media with all the properties described in claim 1.
4. A method of manufacturing ion exchanger directly by condensation or polymerization using the amine salt of the polyvalent acid, or amine salt of polyvalent acid in the amination step.
5. The method in claim 1 where the said acid has at least 1 mobile hydrogen available for exchange.
6. The method of claim 1 wherein the said acid is a polycarboxylic acid, or oxalic acid, or tartaric, or polyacrylic and the like.
7. The method in claim 1 wherein after you recover the metal from the hydroxide eluant solution.
8. The method in claim 1 wherein the acid contains at least one hydroxy acid such as lactic or citric or salicyclic or polymers thereof, but not limited to these acids.
9. The method in claim number 1 wherein the acid contains sulfur, such as phenol sulfonic acid, napthlene tri sulfonic acid, sulfolenes, sulfolanes and the like.
10. The method in claim 1 wherein the acid contains phosphorous such as phosphoric or phosphonic or salts thereof and the like.
11. Where the said acid in claim 2 or 3 may also contain a nitrogen such as nitrilo tri acetate, nitrilotris (methylenephosphonic acid) or methylene amino phosphonic acids and the like.
12. 1 l.
13. The method in claim 1 wherein the anion exchange amine functionality may be modified with any of the above acids or salts for the purpose of selectivity, rate of exchange, modification of basicity of the amine functionality before use.
14. The method of claim 1 wherein the amine functionality can be loaded with metal cyanide and contacted with the above acids simultaneously by using the above acids or salts thereof, and/or mixed with a metal cyanide complex in an aqueous solution wherein both the metal cyanide complex and the above said acid are adsorbed simultaneously for the purpose of the above said characteristics.
15. Wherein the ion exchanger in claim 1 always contains an amine functionality such as primary secondary, tertiary, polyamine, quaternary amine, or mixtures thereof.
16. The method in claim 1 wherein the said metal complex is a cyanide anion metal complex.
17. The method of claim 1 wherein the metal may be a metal cyanide complex and is a precious metal cyanide such as gold, silver or the like.
18. The method of claim 1 wherein metal may be a metal cyanide complex and the metal is a non precious metal such as copper, nickel, zinc or the like.
19. A method in claim 1 where the modified amine functionality can be dissolved in a liquid and be chemically attached to an organic support or an inorganic support.
20. The method of claim 1 wherein you are contacting said exchanger with an aqueous dilute of sodium or potassium anion or any hydroxide solution from 0.1 to 2m to elute the cyanide complex from the exchanger.
Description:
Method for Increased Capacity of Ion Exchange Media Background--Field of Invention This invention relates to the recovery of precious and non precious metals in the mining, refining, and waste treatment industries. No anion exchangers with satisfactory properties were available before anion-exchange resins were invented. The first patents by Adams and Holmes described not only cation exchangers, but also anion exchangers with weak-base amino groups. Later, resins with strong-base quaternary ammonium groups were developed.

Capacity of resin is not only determined by matrix, but by selection of functionality and amine functionality concentration during the manufacturing process of the resin. Therefore, the capacity and characteristics are built into the resin at time of manufacture.

Advances in technology have progressed to enable selectivity to be manufactured directly into some resin, but any gain in selectivity must be paid for by the loss in ion-exchange rate. This effect is observed even with the common weak-acid resins which exchange H+ ions at a considerably lower rate than the strong-acid resins. Also, resins with extreme specificity are difficult to regenerate (except when the preferred counter ion is readily displaced by regeneration) and may even hold chelated counter ions so obstinately that ion exchange no longer occurs. Hence, for any application one should choose the resin carefully, seeking a reasonable compromise between selectivity, ease of regeneration, and rate of ion exchange.

Characteristics, Advantages and Disadvantages of Strong and Weak-Base Resins.

Both strong-base and weak-base resins have similar characteristics, but the advantages and/or disadvantages of one over the other are great and have a profound effect upon their operating efficiency. At varying degrees, temperature, pH, ion strength, agitation, and the presence of competing anions effect the loading capacity and rate of extraction of both strong-base and weak-base resins.

Some of the disadvantages of resins can be overcome, but only at the expense of reducing the claimed advantages. Resins can be eluted at low temperatures and pressures; however, the stripping is generally incomplete and, after a number of cycles, the resin must be incinerated to reclaim the contained metals.

There is a need for an ion exchanger developed specifically for the recovery of metals from cyanide solutions. Development work during the late 1980s has produced weak-base resins with higher pKa values (8-12) which are more suitable for use in cyanide process systems. The ideal ion exchanger should be selective for the cyanide metals in alkaline solutions, have a high loading capacity, be easy to elute and regenerate, and be coarse and physically strong.

Anionic resins are used almost exclusively for the recovery of precious metals from solutions. Anionic resins, both strongly and weakly basic, are employed.

The strongly base resins are generally less selective and more difficult to elute, but they load more rapidly and to a higher level than weak-base resins. Strong- base resins adsorb metal-cyanide complex anions over a broad pH range, including the operating range (10-11) of cyanide solutions. They have a higher loading capacity for the complex anions of precious metals than weak-base resins. Strong-base resins are significantly cheaper than weak-base resins. The main problem with strong-base resins is the difficulty of their elution. In fact, the destruction of the resin has been proposed to recover the adsorbed metals.

Weak-base resins are, by definition, those having primary, secondary, or tertiary amine groups attached to the hydrocarbon matrix. The amine groups become deactivated and stop functioning as ion exchangers above a certain pH. Most weak-base resins have a pKa (50% of the amine groups are protonated at this pH) of 6-8 while the cyanide leach streams are pH 10-11. As a result, only a small percentage of the amine groups in commercial weak-base resins are protonated in the leach stream and as a result have lower loading capacity and slower rates. To increase the capacity of a weak-base resin for cyanide metal, it is necessary to increase the pKa of the resin. According to Riveros and Cooper (1987),"all commercial weak-base resins have a pKa lower than the normal pH of 10-11 of a cyanide (mill) leach liquor. "Hence, the pH of mill solutions has to be adjusted to lower than pKa in order to maintain a reasonable loading of the weak-base resin.

Loading rate of metal cyanide complexes onto strong-base and weak-base resins are similar, but loading capacity of strong-base resins are some two to four times greater than that of weak-base resins. Weak-base resins are limited to loading or do not work at all when the pH of the solution is above 8. If gold and/or other metals are to be loaded onto a conventional weak-base resin, the natural pH value of the cyanide solution containing the gold and/or other metals has to be lowered from about 10.5 to less than 8 if a good capacity is to be achieved. Many weak-base resins are not eluted completely by neutralization with a sodium hydroxide solution. A profound influence on its elution is the presence of strong- base functional groups within the weak-base resin. These are quaternary amine groups, and can be formed when two adjacent tertiary amine groups cross-link.

Their ion-exchange properties are the same as those of the functional groups in a strong-base resin, i. e. the adsorption of anions on these groups is largely independent of the pH value of the solution. The implication is that the aurocyanide, or other metals, that are loaded onto the strong-base groups during adsorption, is not eluted by hydroxide neutralization during the elution cycle.

This gold and/or other metals are therefore returned to the next adsorption cycle, and this results in lower capacity.

Elution of a strong-base resin is possible only by ion exchange unless the anion complex is destroyed, whereas deprotonation of a weak-base resin (R=H) removes the positive charge which enables it to interact with anions. The elution of weak-base resins by both neutralization and ion exchange is possible, these have an advantage over strong-base resins. Weak-base resins are usually eluted with dilute sodium hydroxide solution, which is far easier than the elution of strong-base resins. Only gold and copper are eluted efficiently. Poor elution of nickel, zinc, iron and silver is due to precipitation within the matrix of insoluble metal. They can be removed by washing with NaCN or dilute mineral acid after the elution cycle. Thus, all anionic cyanide complexes are stripped in elution and regeneration to full capacity with inexpensive and less toxic chemicals.

Background--Description of Prior Art At present, for the purpose of metal extraction or other ion exchange processes, weak base anion exchangers are limited to holding capacity and normally have decreased efficiency at high pH levels. For example, Fleming and Cromberge state that Duolite A7 resin at pH6 had a gold loading capacity of only 8.75 g/kg.

Additionally, weak base anion exchange media has a decreased efficiency or may not work above pH9. Most ion exchange media in use today for cyanide metal recovery have to be incinerated to liberate the metals; therefore, they are limited to one usage while creating an environmental hazard. Most others are limited to the number of times they can effectively be regenerated.

Prior Art References U. S. Patents Document Name: Recovery Of Precious Metal Document Number: 5,198,021 Class: 75 Subclass: 744 Issued: Mar. 30,1993 Filed: Mar. 18,1992 Title: Recovery Of Precious Metal Inventor: Michael J. Virnig The example of this invention is apparent in U. S. Patent issued March, 30,1993 to the Henkel Corporation, Michael J. Virnig inventor. It describes recovering precious metal from ion exchange resin using a modified eluant consisting of sodium hydroxide and a carboxylic acid or salts thereof. He said the preferred eluant is sodium benzoate and sodium hydroxide. He also mentioned using a monocarboxylic acid, a modified carboxylic acid, a water soluble salts of polycarboxylic acid, salts of sulfonic acid and phosphorous organic acids may also be used. Salts of polycarboxylic acids such as polyacrylic acid may also be employed along with the other acids mentioned. The composition of the modified eluant solution increases the efficiency of the removal of the gold from the ion exchanger as opposed to the unmodified eluant.

In column 12, of this patent, lines 36 through 45 it states,"To consider the possibility that the benzoate anions which replaced the gold cyanide on the resin would be so strongly held that the resin loading capacity would be reduced in the second loading cycle, the NaOH-Na benzoate eluted resin was thus subjected to the column loading test. The GLC was 38,300 mg/kg and the ratio of gold to metal concentration ( [Au]/ [M]) was 0.63. These results are very similar to those found for the guanidine resin G in the first loading cycle". It was surprising that the loading capacity of the second cycle was the same as the first cycle using the modified eluant considering the possibility that the sodium benzoate would load on the ion exchange resin. He assumes it would nullify the ion exchange sites, thus decreasing the capacity. But, to his surprise the capacity remained the same.

If he had used a polycarboxylic acid instead of a organophosphorous acid, or a phosphoric acid, or salts thereof, he would have discovered an increase in loading capacity because of the number of mobile hydrogens which are present in the polycarboxylic acids or the phosphoric acids.

Document Name: Adsorption and Elution of Metal Document Number: 5,156,825 Class: 423 Subclass: 24 Issued: Oct. 20,1992 Filed: Sept. 26,1990 Title: Adsorption and Elution of Metal from Ion Exchange Inventors: S. V. Sarma & D. M. Steed U. S. Patent 5,156,825 issued October 20,1992, titled Adsorption and Elution of Metal from Ion Exchange Resin is a prime example of the unobviousness of my invention. In this invention S. V. Sarma and D. M. Streed state in column 4 lines 63 through 65 that"the resin capacity of Duolite A368 is about 250 troy ounces of gold per cubic foot of resin when operated under ideal conditions."This means the weak-base ion exchange resin Duolite A368 has the ability to adsorb about 10,000 ounces of gold per ton.

An article titled;"The Extraction of Gold from Cyanide Solutions by Strong and Weak-base Anion-exchange Resins"published in the Journal of the South African Institute of Mining and Metallurgy, May 1984 by C. A. Fleming and G. Cromberge contradicts the statement in the Sarma and Streed patent. On page 136, Table XI it shows the same weak base Duolite A368 has only an adsorption capacity of 3.5 troy ounces per cubic foot. Sarma and Steed missed an unobvious contradiction. The solutions to which they subjected the ion exchange resin contained some of the same polyvalent acids as conducting salts that were in the article on negative rejection of the cyanide metal complexes.

In addition, another U. S. patent 4,076,398 assigned to the AMP Corporation, was issued Feb. 28,1978, titled"Method, Electrolyte and Additive for Electroplating a Cobalt Brightened Gold Alloy."With reference to Electroplating Technology Recent Developments, Chemical Technology Review No. 187, page 202. This gold plating patent discusses the containing of conducting salts such as, potassium citrates, or potassium phosphates and a salt of nitrilotriacetate. Obviously these salts are adsorbed on the ion exchange resin with the gold and also should have decreased the capacity, but surprisingly did not. The capacity was actually increased.

Publications Publication Name: Separation Science and Technology 18 (5), pp. 461-474,1983 Publication Date: Oct. 02,1981 Number of Page: 14 Title: Negative Rejection of Group Ib Metal Cyanide Complexes in the Hyperfiltration by Cellulose Acetate Membranes. Donnan Membrane Effect Authors: Takashi Hayashita, Makoto Takagi, and Keihei Ueno Publication Name: Separation Science and Technology 22 (2&3), pp. 487-502,1987 Number of Pages: 16 Title: Selective Solvation Extraction of Gold from Alkaline Cyanide Solution by Alkyl Phosphorus Esters.

Authors: J. D. Miller, R. Y. Wan, M. B. Mooiman, and P. L. Sibrell An article published in SEPARATION SCIENCE AND TECHNOLOGY, titled "Negative Rejection of Grp Ib Metal Cyanide Complexes in the Hyperfiltration by Cellulose Acetate Membranes. Donnan Membrane Effect", authored by Takashi Hayashita, Makoto Rakagi and Keihei Ueno. This article states that particular acids assist in the migration of Cu (CN) 2-, Ag (CN) 2-, and Au (CN) 2- through the cellulose acetate membrane forming some type of a mobile complex which is described as a phenomenon. They talk about these particular acids causing selectivity to allow only those metals to pass through the membrane on to the other sites to build up the concentration. The CN metals such as Ni, Zn, Iron stay behind, they are not affected by this phenomenon.

The second part of the phenomenon taking place is with modification of basicity of the amine functionality. Citric acid, phosphoric acid, tartaric acid and the like are also pH modifiers (buffers). These articles entitled"Developments In Impregnated and Ion Exchange Resins for Gold Cyanide Extraction."and "Selective Solvation Extraction of Gold from Alkaline Cyanide Solution by Alkyl Phosphorus Esters,"describes using modifiers to shift amine basicity to a more alkaline side so that the amines will function as ion exchangers under pH conditions of 10,11, and 12. Increased basicity of the amine or the amine functionality widens the pH working range of the functionality allowing higher capacity and faster rates of adsorption. Thus, by choosing the amine functionality of desired basisity and choosing the correct polyvalent acids or modifiers, one can make the ion exchanger work at virtually any pH to adsorb any cyanide metal complex. Resulting in high loading capacity, high selectivity of certain metals while rejecting other cyanide complexes.

It is apparent that the phenomenon of negative ion rejection, as described and utilizing it in an application of ion exchange, was entirely overlooked by the authors of the article on negative rejection, and the inventors of the AMP and Henkle patents (US5156825 and US5198021). In no way did they describe or explain the discrepancy of their results for gold loading capacity of their ion exchange resin in contradiction of what Fleming & Cromberge stated in their gold extraction article. There's a major discrepancy, 10,000 ounces per ton vs.

75 ounces per ton for the same exact material. Mr. Virnig in the Henkel patent also made the same error by not understanding that something is happening through the hydrogen of the benzoic acid. THAT ITS FUNCTIONALITY IS ALLOWING THE AU (CN) 2 TO BE ADSORBED ONTO THE BENZOATE RATHER THAN ONTO THE AMINE FUNCTIONALITY, AND, BY THAT HAPPENING, IT CORRESPONDS TO THE PHENOMENON OF NEGATIVE REJECTION. By combining the mechanisms in the article"Removal of Organic Acids from Wine by Adsorption on Weak Basic Ion Exchangers', page 1481 at the bottom and page 1483 at the top, examples 9 through 12 describes the mechanism of adsorption of the acid. The acid still having mobile hydrogen available for ion exchange. Example 11, one exchange, example 12, two exchanges. The mechanism in the Henkel and AMP patents relate to the ability of the acid anion to give up mobile hydrogens to form available exchange sites.

The more exchange sites it has, the more Cu, Ag, Au, it can hold. In the case of the Henkel patent, it describes benzoic acid which has just one mobile hydrogen to give up. Hence, there would not have been any increase or decrease. If he had used a polyvalent acid instead he would have seen a capacity increase, because of the multiple mobile hydrogens available for exchange. He was seeing the mechanism of my invention, but could not explain or understand its results and/or effets. Mr. Virnig said in patent 5,198,021 column 12 lines 36 through 42."To consider the possibility that the benzoate anions which replace the gold cyanide on the resin would be so strongly held that the resin loading capacity would be reduced in the second loading cycle". What it did was it used the hydrogen of the benzoic acid to do the exchanging rather than the amine functionality to do the exchanging. Apparently, the hydrogen was doing the exchange as described in the article on"Impregnated Solvent Extraction."It describes that in order for the process to function and gold cyanide to be adsorbed into the amine functionality, it has to be in the hydrogen cycle. By being in the hydrogen cycle it means a hydrogen being given up. Since these buffering acids have more than one hydrogen, one of them is used to attach the acid to the amine functionality. The other hydrogens are used to adsorb the cyanide metals Au, Ag, and Cu. We see the increase in capacity because the modified amine polyvalent acid functionality is in the hydrogen cycle and by utilizing the buffering ability we keep it in the hydrogen cycle. Thus, by choosing the right buffering multivalent acids we operate the exchanger at the desired pH range.

U. S. Patent Document Name: Carboxylated Cellulose Document Number: 4, 260,740 Class: 536 Subclass: 63 Issued: April 07,1981 Filed Oct. 10,1979 Title: Carboxylated Cellulose Ion-Exchange Materials Inventors: Roy Carrington & Michael C. Hall This U. S. Patent 4,260,740 issued April 7,1981 titled Carboxylated Cellulose Ion-Exchange Materials, describes the process by which the inventors react citric acid and cellulose to form cationic ion exchangers which are capable of exchanging mobile hydrogen's for metal ions. These mobile hydrogen's are able to exchange for cationic metals such as Cu, Au, etc.

It is very apparent that the scope of my invention is unobvious to those skilled in the arts.

Objects and Advantages One of objects of my invention is to manufacture a new basic ion exchange media with increased capacity and a higher exchange rate, or increase the capacity and rates of already available ion exchange media material by a simple process. As an example, Fleming and Cromberge state that Duolite A7 ion exchange media at pH6 has a loading capacity of 8.75 g/kg. By application of my invention the loading capacity of the same Duolite A7 was increased to 347 g/kg. Another object of my invention is to increase the apparent basisity (pKa) of the amine functionality by using the appropriate pH modifiers. Another object is to decrease the basisity of a high pKa amine functionality to a lower apparent basicity to increase the elution efficiency without using a modified eluant. i. e. dilute sodium hydroxide to remove all the metals. For example, a guanidine functionality of a pKa of 13.5 can be shifted downwards to an apparent pKa of 11 by using the proper pH modifier. Another objective is to improve selectivity of amine functionality. Still further objects and advantages will become apparent from a consideration of the ensuing description.

Summary This invention is a method for increasing the metal holding capacities of ion exchangers by the addition of an auxiliary anion containing one or more exchangeable mobile hydrogen's. Preferably these auxiliary anion excerpt a pronounced buffering effect on the functionality. These auxiliary anions may also increase the selectivity of the amine functionality without decreasing capacity. It has been discovered that certain compounds having multivalent acid groups provide a method for increasing ion exchange capacity and/or modify the pKa of weak base anion exchanger towards the buffering range of the multivalent acid compounds, and also increasing the selectivity of the amine functionality. These compounds may be phosphorous containing acids or salts, or sulfur containing acids or salts, boron containing acids or salts, hydroxy carboxylic acids, poly carboxyl organic acids or amine salts and the like, or polymers, thereof containing phosphorous or boron or sulfur or amine acids or mixtures thereof. The process can be incorporated, during the manufacturing, prior to the adsorption cycle or simultaneously during adsorption cycle with equal results. By choosing the right auxiliary anion the basicity of the amine functionality can be shifted upwards or downwards to utilize the best operating condition to the solution that it is used with. It is preferable but not necessary to use mixtures of the auxiliary anion to incorporate specific characteristics to the amine functionality. These characteristics being selectivity for a certain ion, operating at a specific pH having a certain capacity and having high exchange rates in the presence of certain counter ions.

Preferred Embodiment-Description and Operation It is my intention to bring forward this concept as a new invention not known to those skilled in the art. This invention is the creation of new types of basic ion exchange amine functionality either by manufacture of, or chemical alteration of, existing basic anion exchanger. By the combination of the amine functionalities, and the polyvalent acid to form a new functionality (hybrid) with increased ion exchange sites which are stable under adsorption and elution cycles. Existing anion exchange theory is when the anion exchange adsorbs the anion and is exhausted or 100 percent exchanged. Further anion exchange cannot take place until the ion exchanger is regenerated. The anion has to be removed in order to allow that functional group to be regenerated. It has been discovered that polyvalent acids or salts have the ability to act as arms or ligands to increase the amount of exchange sites on the amine functionality available, thus increasing the capacity. Since it has increased sites for anion exchange, the kinetics are also increased by having increased activity sites. It has further been discovered that certain polyvalent buffering acids have the ability to shift the apparent pKa of the amine functionality's into the buffering range of the polyvalent acid used.

The present invention can be applied to any type amine functionality; for example, liquid ion exchangers (solvent extraction) organic ion exchangers such as styrene DVB, foams, etc. Other organic matrixes such as cellulose, hydrogels, chitosans, etc. Other supports such as activated carbon where the amine functionality is either impregnated or chemically bound. Solvent impregnated, inoganic adsorbants, an/or inert ion exchangers containing chemically bound amine functionality's, such as zeolites, ceramics and the like.

This list is not intended to limit the scope of the invention, but is merely to demonstrate the versatility of the invention. All that is required is amine functionality's to utilize this invention to improve the characteristics. For example, amine functionality with a pKa of 8, by applying an auxiliary functionality such as phosphate forming an amine phosphate modified functionality. That phosphate functionality being a mono basic phosphate salt, buffers to the range of pH 10. Now the apparent pKa of the amine functionality and phosphate fiunchas two mobile hydrogen's for exchange sites of the cyanide metals in the cyanide solution. The aqueous solution containing the cyanide metal is contacted with the (modified) amine functionality whereby the cyanide metal is extracted or removed from the aqueous solution, and the modified amine functionality containing the cyanide metal is separated from the aqueous solution now substantially barren of the cyanide metal. The amine functionality can be eluted with dilute NaOH at room temperature. Since many of the polyvalent acids are in themselves buffering agents they act as exchangers for Na or H. By that taking place the difficulty in weak base exchangers operating above it's normal pKa by utilizing these polyvalent acids buffering ability, we can broaden basisity (pKa) of the exchanger. By forming an amine acid salt with an apparent higher basisity (pKa) we can at the same time increase the capacity by increasing the number of sites available for exchange. By raising the pH above the buffering for example, a higher pH free base forms quickly; thus, regeneration or elution of the adsorbed anionic species takes place, but the polyvalent acid is not removed. Regeneration takes place under milder conditions. Likewise a guanadine amine functionality with a pKa of 13.5 being treated with the same auxiliary anion after being treated with the same polyvalent acid now has an apparent pKa of about 10. Thus, subjected to the same cyanide solution the amine functionality adsorbs the cyanide metals, and then can be easily and efficiently eluted at room temperature by the same dilute NaOH solution.

It has been further discovered that these polyvalent buffering acids also exhibit a coordinating chelation effect on the metal ion being adsorbed. This apparent chelation effect substantially increases the selectivity of the modified amine functionality for certain cyanide metals i. e. such Cu (CN) 2-, Ag (CN) 2-, Au (CN) 2- which are linear cyanide metals. Cu (CN) 3, Cu (CN) 4, Ni (CN) 2 and Zn (CN) 2, Co (CN) 3, Fe (CN) 3 which are not linear cyano complexes are rejected by the amine modified functionality. It has also been discovered that this invention works on all amine functionality's. We call these polyvalent acids or salts (additional) auxiliary functionality's. These in themselves, when placed on an amine functionality have the ability to exchange sodium, potassium, etc. for hydrogen. Thereby being an anion exchanger acts as anion or cation or both simultaneously. An example of this is an anion exchanger adsorbing a polyvalent acid in the hydrogen form H+-H+ Resin--NOH RH+- H+ H+ Resin--N-R---H+ H+ coming in contact with a solution containing sodium ions, such as aqueous sodium chloride. An exchange of sodium in the liquid for the hydrogen on the ion exchanger takes place. The effluent has now become HCL and will continue until all the hydrogen are replaced by sodium.

This process works on all types of amine functionality's. For example, a weak- base anion exchanger adsorbing a metal CN anion, where the said exchanger is in the sodium form, the exchanger will exchange. If you pass a liquid containing a metal CN, pH4 through an anion exchanger (of the invention) adjusted with NaOH, KOH, etc. to pH10 (sodium form) but has been washed with DI water to neutralization (pH7). The effluent will be devoid of metal CN and the pH will have risen to about pH10. The opposite of that an alkaline metal CN bearing solution philo adjusted with NaOH, KOH, etc. passing through an ion exchanger in the hydrogen form washed with DI water to neutralization (pH7), the exchanger will adsorb both metal CN and the Na+ or K+. The effluent will be void of metal CN anion and of metal CN anion and of sodium or potassium, etc. and the pH will be about 4. Thus, the exchanger (modified anion) functioned as an anion and cation exchanger simultaneously.

It is known to those skilled in the art that when the ion exchanger is manufactured the capacity and other characteristics are predetermined and manufactured into the ion exchanger and cannot be altered thereafter. By incorporating this invention the capacity can be increased many times over its initial capacity. This is because of the presence of additional mobile hydrogen's contained in the auxiliary anions, which are placed on the amine functionality which now form the new exchange sites. Obviously it becomes apparent how the exchange capacity can be increased.

It is apparent now to those skilled in the art the versatility and application of this invention are beyond the scope of prior art by means of a simple inexpensive method. Desirable characteristics can be introduced into an exchanger to fit a specific application, tailored made for it with higher efficiency in all areas of operation. These can be incorporated into the ion exchanger, at time of manufacturer or post manufacture, any or all of these characteristics can then be incorporated into the ion exchanger. Thus at the time of application, the desired characteristics can be altered or added to the existing ion exchanger.

To illustrate the features of my invention the following examples of chemical alteration of existing weak base resins are given.

SPECIFIC EXAMPLES Example 1 A weighed treated sample of commercial ion exchange media Duolite A7 was treated with a solution of potassium gold cyanide adjusted to pH4 with HCL.

After 24 hours the sample ion exchange media was washed and decomposed to determine gold content. The percent gold was 0.11%.

Example 2 A weighed sample of commercial ion exchange media Duolite A7 was treated with a drag out solution containing gold cyanide, potassium citrate, and citric acid at pH4. After 24 hours the ion exchange media was removed from the liquid and washed with DI water. The ion exchange media was than decomposed to recover the gold contained. The percent of gold was 35.5%.

Example 3 A weighed sample of commercial ion exchange media Duolite A7, placed in a column was treated with the same type of solution used in example 2 at pH4.

After the gold was adsorbed by the ion exchange media the gold was removed with NaOH. The process of loading and removal was performed 10 times. A weighed sample of that material was then subjected to the process of Example 2 to determine gold capacity. The gold capacity had increased to 44+ percent gold contained.

The following three examples demonstrate treating the ion exchange media according to the invention prior to gold adsorption.

Example 4 A weighed sample of commercial ion exchange media Duolite A7 was treated with a solution of potassium citrate, adjusted with citric acid to pHlO. The ion exchange media was allowed to be in contact with the solution for 24 hours, then removed from the liquid. Potassium gold cyanide was added to that liquid and the pH again adjusted with citric acid to a pH4. All concentration of components were the same as in Examples 1,2, and 3 and the ion exchange media placed in contact with the liquid for 24 hours. After 24 hours the ion exchange media was removed from the liquid, washed with DI water, and decomposed to recover the gold. The percent gold removed was 67.47%.

Example 5 As in Example 1, a treated sample of commercial ion exchange media Duolite A7 was treated with a solution of potassium gold cyanide adjusted to pHlO. The weighed sample was washed and decomposed to determine gold content. The gold content percent was 0.07%.

Example 6 Example 4 was repeated, but instead the liquid was adjusted to pHlO. The gold content percent was 7.5%.

For those skilled in the art, this process can also be used for manufacturing directly into the high capacity ion exchanger described in this invention. For, example, by substituting the amine salt of the polyvalent acid for the free amine (amine salt) during the condensation process or amination process.

To illustrate the features of my invention the following examples of the preparation of ion exchange media are given. It is understood that the invention is not limited to the details of procedures contained in these examples.

Example 7 An ion exchange media similar to Duolite A7 is manufactured by reacting tetraethylenepentamine, formaldehyde and phenol under acidic condensation conditions using phosphoric acid at a pH between 1 and 2. The tough solid which results is allowed to stand overnight then ground and dried at 70 degrees C for 12 hours, screened at 20 to 60 mesh, washed and regenerated with dilute sodium hydroxide. The above ion exchange media was treated as in Example 1.

It adsorbed 67 percent gold by weight.

Example 8 An ion exchange media of a urea formaldehyde type is produced by reacting a mixture of urea, formaldehyde and guanidine citrate under alkaline conditions between pH 9 and 10, for about 4 hours under reflux. The pH is reduced to 7 with citric acid and then cooled, thereby gelling the material. The material is allowed to stand for 24 hours, then ground and dried at 70 C for 12 hours, screened at 20 to 60 mesh, washed and regenerated with dilute sodium hydroxide. Treated as in Example 1, it had high gold adsorbing capacity as experienced in Example 7.

Example 9 An ion exchange media of an acrylic divinylbenzene type consisting of copolymers of acrylonitrile and divinylbenzene (AN-DVB) were polymerised by suspension polymerization. Amenolysis with amino guanidine phosphate is carried out using its solution in butanol in the presence of sodium carbonate water mixtures, refluxing polymer for desired time. The ion exchange media had a high adsorbing capacity for gold as experienced in the prior two examples.

Example 10 A commercial ion exchange media Amberlite IRA400CL was treated with monosodium, NTA (nitrilotriacetic acid). A solution containing 100 ml of 200 ppm Ni++ buffered with acetate to pH4 is contacted with 50 grams of the treated Amberlite IRA400CL for one half hour. Measured by AA (atomic adsorption) the Ni concentration in solution was 0.8 ppm.

Example 11 50 grams of Amberlite IRA400CL was placed in a solution containing 100 ml of 200 ppm Ni++ buffered with acetate to pH4 for one half hour. The Amberlite IRA400CL was removed and analyzed the liquid by atomic adsorption for Ni concentration. The concentration was 200 ppm.

Example 12 A substituted guanadine containing two phenol groups was prepared and dissolved in butanol and impregnated into a porous organic support. The solvent was removed by evaporation. A portion of the impregnated material was treated with a solution of potassium gold cyanide, adjusted to pH 10. The sample was treated as in example 5. The gold content percent was 0.1%.

Example 13 Another weighed sample of the impregnated material was treated with phosphoric acid phosphate solution, pH 10 for 24 hours. Potassium gold cyanide was added, the pH was adjusted to 10 for 24 hours. The gold content was analyzed to be 22.83%.

The examples do not limit the scope of the invention. The process can be used on any of the known manufactured ion exchangers. The matrix of the resin does not affect the ion exchange capacity, but is more affected by the condition at which the exchange is expected to adsorb, pH, ionic strength or other physical properties. The operating conditions can be altered by utilizing the different poly acids (buffering shift) the basicity of the amine (pKa), the character of the matrix, porosity, hardness, which are well understood by those skilled in the art. Thus, a resin can be manufactured which has all the ideal characteristics such as pH, density, hardness and high adsorption capacity. Until this invention it has not been able to be produced (manufactured) meeting these conditions with prior art.

Conclusions, Ramifications, and Scope Accordingly, it can be seen that with this invention it is possible not only to manufacture a new weak-base ion exchange media that has all the ideal characteristics, but it is also possible to alter current existing ion exchange media enabling them to have the same ideal characteristics. Those ideal characteristics such as, effectively operating in higher pH range, excellent density and hardness, and very high adsorption.

Although the description above contains many specificity, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention.

Various other embodiments and ramifications are possible within its scope.

Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.