WO2012151028A1

WO2012151028A1 - Process for recovery of base metals

Info

Publication number: WO2012151028A1
Application number: PCT/US2012/032687
Authority: WO
Inventors: Joseph L. Thomas
Original assignee: METALS RECOVERY TECHNOLOGY Inc A DELAWARE Corp
Current assignee: METALS RECOVERY TECHNOLOGY Inc A DELAWARE Corp
Priority date: 2011-05-03
Filing date: 2012-04-09
Publication date: 2012-11-08
Anticipated expiration: 2013-11-03

Abstract

A process for the recovery of selected base metals from a solution includes selectively precipitating metals from the solution using substituted quaternary ammonium salts (SQAS). SQAS is generally represented by the formula H0-3 R4-1 NX where H = hydrogen, R = organic group, N = nitrogen and X = halide. Selective precipitation for separation employs variation in organic solvents, heating, cooling, oxidation, pH, and reduction of SQAS complexes.

Description

TITLE

PROCESS FOR RECOVERY OF BASE METALS

BACKGROUND OF THE INVENTION

The field of the present invention is processes for the separation of base metals.

Recovery, separation and purification of many metals are typically tedious processes requiring repeated application of pyrometallurgical, hydrometallurgical or electrowinning processes to achieve acceptable metal recovery and metal purity. Most source materials such as ores, spent catalysts, plating solutions, sludges, ore concentrates and smelter mattes are chemically complex, not only because of the diversity of metal elements but also because of the presence of large quantities of non-targeted metals in the source materials. Recovery, purification and separation of metals from these source materials can be difficult, time consuming, expensive, and unsatisfactory with respect to some elements.

Solvent extraction and/or ion exchange are regularly used for such separations. Other chemical processes of precipitation and volatilization may be used in conjunction with solvent extraction and/or ion exchange. Typically, these processes are used to remove selected elements from the mother liquid or to purify metals of insufficient purity.

To meet the demand for valuable metals, the industry is in need of a simpler, lower cost and cleaner alternative to current practices that is capable of recovering metals from chemically diverse primary and secondary sources.

SUMMARY OF THE INVENTION

The present invention is directed to a process for the recovery and purification of selected base metals, the term "base metals" as used herein excludes precious and noble metals as those terms are used in the field of chemistry. "Base metals" specifically includes but is not limited to Co, Cu, Fe, Ni, Pb, Se, Te, and Zn. In the process, substituted quaternary ammonium salts (SQAS) are employed to separate base metal(s) through selective precipitation in aqueous and non aqueous solutions. Although not to be bound to any particular hypothesis, it appears that most metals that form anionic complexes can be precipitated with SQAS. The stage at which various of the base metals are recovered through precipitation or retention in solution depends on conditions in the solution and the solvent.

Thus, a process for the recovery of base metals comprises selectively separating at least one of a plurality of metals in a solution by precipitating the at least one metal using SQAS and removing the precipitate from the solution. The SQAS may be defined as H₀-₃ R₄-i NX where H = hydrogen, R = organic group, N = nitrogen and X = halide. The metal(s) selectively separated may be capable of forming an anionic complex.

[0001] In a first application, the at least one metal includes one or both of Pb+4, Fe+3 and one or more of lower valent metals Ni, Se, Zn, separation being in a solution in 6N HCI and SQAS.

In a second application, the at least one metal includes Te and Se, separation being in a solution in 6N HCI and SQAS.

In a third application, the at least one metal includes Ni and Co, separation being in a solution with SQAS with increasing acid concentration.

In a fourth application, the at least one metal includes Cu+2, Zn+2, Co+2 forming anionic complexes, separation being in methanol with SQAS.

In a fifth application, the at least one metal includes Co+2 forming anionic complexes, separation from Ni being in methanol with SQAS.

Thus, it is an object of the present invention to provide improved processes for the recovery of certain base metals. Other and further objects and advantages will appear hereinafter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Substituted quaternary ammonium salts (hereinafter SQAS, singular and plural) can be made to precipitate certain metals from aqueous or organic solvents. This property can be used to effect separations of one metal from another. Although not to be bound to any particular hypothesis, it appears that most metals that form anionic complexes can be precipitated with SQAS.

The recovery of precious metals, as that term is used in the field of chemistry, using SQAS is disclosed in U.S. Patent No. 7,935, 173, the disclosure of which is incorporated herein by reference. In the recovery of precious metals, precious metals precipitated while base metals generally remained soluble under the conditions employed. It was not expected, therefore, that base metals might also be recovered using SQAS. As will be shown below, utilization of different solvents and acid strengths do allow separation of selected base metals and provides a route for their purification. Normally difficult separations of Co/Ni and Se/Te are of particular note.

In a preferred embodiment, metals are precipitated with SQAS. The SQAS are described by a general formula: H₀-₃ R₄-i NX where H = hydrogen, R = organic group, N = nitrogen and X = halide.

Numerous SQAS of metals have been synthesized and characterized, see J. W. Mellor, a Comprehensive Treatise on inorganic and Theoretical Chemistry, Vol. XV (Longmans, London 1936), the disclosure of which is incorporated herein by reference. In the preferred processes, complexes of dimethylammonium chloride, trimethylammonium chloride, tetramethylammonium chloride, and tetraethylammonium bromide have been investigated. Other SQAS conforming to the general formula with desired characteristics are likely to form suitable metal- SQAS complexes. Tetramethylammonium chloride is preferred because it meets desirable characteristics, is widely available, is of low cost and does not result in mixed halides in solution when added to metal liquors that are typically in hydrochloric acid.

Metal recovery and refining includes processes of heating, cooling, precipitation, dissolution, oxidation and reduction of SQAS complexes. Metal- SQAS precipitation is accomplished in all cases discussed, typically after cooling of a solution. Precipitates are physically separated from filtrates by filtration, centrifugation, evaporation or other suitable method. Many separable metals can remain in the filtrate in certain of the processes. In specific instances, metal- SQAS precipitates form in organic solvents such as alcohols, while they do not form in aqueous solvent.

In dilute acid such as 6N HCI, lower valent metals such as Pb+2, Fe+2, Ni+2, Se+3, Zn+2, and Cu+2 are soluble in the presence of SQAS. However, Pb+4, Fe+3 readily precipitate. Therefore Pb and Fe can be separated from Ni, Se, and Zn by oxidation with chorine.

Historically, clean separations of Se and Te are difficult. However, in 6N HCI, Te precipitates quantitatively in the presence of SQAS while Se is totally soluble. This excellent separation is simple and yields Te with a purity exceeding 99.9%.

Nickel-Cobalt separations are likewise very difficult. However, since nickel does not form anionic complexes, it is not precipitated by SQAS. Cobalt is precipitated by SQAS and solubility decreases as acid concentration increases.

Cu+2, Zn+2, Co+2 and other metals usually soluble in the presence of SQAS, do form anionic complexes. These complexes can be made to precipitate by dissolving the metals in organic solvents and adding SQAS. For example, Cu, Zn, and Co chlorides are readily soluble in methanol. If SQAS is added to these soluble salts, yellow Cu, blue Co, and white Zn complexes precipitate.

In addition, similar to chlorides, successful SQAS precipitates with anionic base metal nitrite complexes in aqueous or methanol solution can be formed. Thus it appears that application to a wide variety of anions is possible.

SQAS is contemplated to separate many types of metals as shown by the examples below. Although we cannot attest to any particular theorem, recovery and purification of metals utilizing SQAS appears to reduce inherent constraints imposed by thermodynamic and kinetic properties of metal in solution that have long defied resolution.

The following examples illustrate the described process:

RECOVERY AND PURIFICATION FROM HYDROCHLORIC ACID

Example 1

Selenium and

Tellurium

Dissolve 1 gram each of Se and Te in 6N HCI to yield a

chloride solution of metals

Add 8 grams of tetramentylammonium chloride

and heat to boiling

Cool solution and

filter ppm Se ppm Te Purity

Filtrate after

precipitation 18, 1 19 53 99.7%

Sample of residue

in water 3 224 98.7%

Recrystallization of residue in 6N

HCI 1 14,229 99.996%

Example 2

Nickel and Cobalt

Saturated 1 2N HCI with 1 gram NiCI2

gram CoCI2.6H20

Added 8 grams

tetramethylammoniumchloride

Immediate blue

precipitate

mq Ni mq Co

Original solution 143 434

Filtrate after

precipitation 143 182

% Co ppm Ni ppm Co Co Purity Recovered

Sample of residue

in water 5 18,000 99.97% 58%

RECOVERY AND PURIFICATION FROM ORGANIC SOLVENTS

Example 3

Nickel and Cobalt

Dissolved 1 gram of NiCI2 and 3 grams of CoCI2 in 20 ml of

methanol

Added 2 ml 12N HCI

Added 3 grams tetramethylammoniumchloride and immediate blue precipitate obtained

Filtered solution

ppm Ni ppm Co

Original solution 3,875 12,000

Filtrate after

precipitation 3,250 140

Purity % Co Recovered

Sample of residue in

water 11 12,000 99.91 % 99% Example 4

Copper and Zinc

Saturated methanol solution of metal

as: CuCI2 ZnCI2

ml methanol 5 5

ml 12N HCI

Grams tetramethylammonium chloride

added

Color of precipitate yellow white

Residual ppm metal in solution after

filtration 766 89

Thus, a process for the recovery, separation and purification of base metals is disclosed. While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein. The invention, therefore is not to be restricted except in the spirit of the appended claims.

Claims

Claims:

1 . A process for the recovery of base metals, comprising

separating at least one base metal in a solution by precipitating the at least one metal using substituted quaternary ammonium salt (SQAS).

2. The process of claim 1 , (SQAS) being H₀-₃ R₄-i NX where H = hydrogen, R = organic group, N = nitrogen and X = halide.

3. The process of claim 1 , the at least one metal being capable of forming an anionic complex.

4. The process of claim 1 , the at least one metal including one or both of Pb+4, Fe+3 and one or more of lower valent metals Ni, Se, Zn, separating being in a solution in 6N HCI and SQAS.

5. The process of claim 1 , the at least one metal including Te and Se, separating being in a solution in 6N HCI and SQAS.

6. The process of claim 1 , the at least one metal including Ni and Co, separating being in a solution with SQAS and increasing acid concentration.

7. The process of claim 1 , the at least one metal including one of Cu+2, Zn+2, Co+2 forming anionic complexes, separating being in methanol with SQAS.

8. The process of claim 1 , the at least one metal including both Co+2 and Ni, separating being in methanol with SQAS.

9. The process of claim 1 , the at least one metal being in an anionic nitrite complex