Claims:We Claim,

[CLAIM 1]. A method for recovering cobalt and copper from White-alloy or Alliageblanc comprising:
(a) Pulverizing the white alloy granules to about 100 to 300 mesh;
(b) 1st stage leaching: treating the white alloywith sulphuric acid solution at pH 1-1.5 and temperature 70-800C, wherein Cobalt and Iron are leached in solution as cobalt sulphate and ferrous sulphate;
(c) 2nd stage leaching: treating residue form step (b) with sulfuric acid, reductant and oxidant at pH: 0.2-0.5;
(d) Leached solution from step (b) is further processed for removal of iron;
(e) The purified leach solution from step (d) is treated for recovery of cobalt;
(f) the residue remain after cobalt recovery further treated with sulfuric acid and reductant-oxidant (pH: 0.2-0.5) to get higher metal recoveries, sodium metabisulphite or potassium metabisulphite and one oxidant selected from the group consisting of sodium hypochlorite or hydrogen peroxide or nitric acid at 70-80 0 C temperature with a lesser dosage compared to 2nd stage cobalt leaching and higher acidity in copper leaching.
(g) The residue generated after copper leaching is recycled back to copper leaching for copper recovery.
(h) Copper spent electrolyte (CuSE) form copper electrowinning (CuEW) is recycled to Cobalt leaching for cobalt recovery;
(i) The iron cake generated from the iron removal step (c) is either sale or send to land filling site.

[CLAIM 2]. The method for recovering cobalt and copper as claimed in claim 1 wherein pulverizing the white alloy to powder using vibrating mill or melting and air or water atomized.

[CLAIM 3]. The method for recovering cobalt and copper as claimed in claim 1 wherein process for removal of iron is by atmospheric pressure or autoclave pressure.

[CLAIM 4]. The method for recovering cobalt and copper as claimed in claim 1 wherein oxidant selected from the group consisting of hypochlorite or hydrogen peroxide or nitric acid.

[CLAIM 5]. The method for recovering cobalt and copper as claimed in claim 1 wherein reductant selected from the group consisting of sodium metabisulphite or potassium metabisulphite.

[CLAIM 6]. The method for recovering cobalt and copper as claimed in claim 1 wherein recovery of cobalt comprises: 1st stage solvent extraction (SX) for impurities removal using phosphoric acid organic reagent followed by 2nd stage solvent extraction (SX) using phosphonic acid organic reagent to recover cobalt as high pure cobalt metal or cobalt salts or precipitate to convert as cobalt products.

[CLAIM 7]. The method for recovering cobalt and copper as claimed in claim 1 wherein two stage leaching process cobalt and iron metal are selectively leached from copper in soluble form. Selectivity of cobalt over copper is 99.5 %.

[CLAIM 8]. The method for recovering cobalt and copper as claimed in claim 1 wherein residue generated from two stage leaching is mainly copper

[CLAIM 9]. The method for recovering cobalt and copper as claimed in claim 1 wherein copper is recovered from residue in acidic medium using reductant (sodium metabisulphite or potassium metabisulphite) and oxidant (sodium hypochlorite or hydrogen peroxide or nitric acid) with using to convert copper to into soluble form followed by CuEW (copper electrowinning) to make copper metal/powder.

[CLAIM 10]. The method for recovering cobalt and copper as claimed in claim 1 wherein Copper spent electrolyte (CuSE) so generated from copper electrowinning (CuEW) is recycled back to copper leaching stage for utilizing free acid for leaching.

[CLAIM 11]. The method for recovering cobalt and copper as claimed in claim 1 wherein residue from copper leaching is very less in quantity and being recycled back to leaching.

[CLAIM 12]. The method for recovering cobalt and copper as claimed in claim 1 wherein recycling of Copper spent electrolyte (CuSE) is continue till cobalt concentrate reaches to approx. 10-15 g/l.

[CLAIM 13]. The method for recovering cobalt and copper as claimed in claim 1 wherein Copper spent electrolyte (CuSE)after reaching cobalt concentrate to 10-15 g/l CuSE is transferred to cobalt leaching for cobalt recovery.

[CLAIM 14]. The method for recovering cobalt and copper as claimed in claim 1 wherein selectivity of copper over cobalt is 99.99 %.

[CLAIM 15]. The method for recovering cobalt and copper as claimed in claim 1 wherein overall copper recovery is 98.76 %.

[CLAIM 16]. The method for recovering cobalt and copper as claimed in claim 1 wherein overall cobalt recovery is 99.42 %.
, Description:FIELD OF INVENTION:
A method for selectively recovering valuable metal such as cobalt, Iron and copper from white alloy or Alliageblanc or similar material containing substantial amounts of iron. The present invention relates to a method for recovering valuable metals such as cobalt and copper from white alloy or Alliageblanc or similar material containing substantial amounts of iron.

BACKGROUND OF INVENTION:
Substantial reserves are known to exist of ores, both of the oxidic and sulfidic types, as well as slags, which contain relatively small high to medium amounts of valuable metals such as cobalt, copper and/or nickel and relatively large amounts of iron. The first step in recovering valuable metals from such ores and/or slags is a pyro-metallurgical reduction process which converts oxides of metals in the ore or slag to metals having a zero-oxidation state. This reduction process is conducted at high temperature in a reduction furnace, and the material produced by the reduction is typically referred to as an "alloy" or "Alliageblanc".

Alloys typically contain about 35 to 70 percent iron, and less than about 10 to 60 percent of valuable metals such as cobalt, copper and/or nickel.

Metals are recovered from alloys by a hydrometallurgical process involving an acidic leach process conducted under oxidative conditions in which all the metals present in the matte or alloy are oxidized and dissolved in the form of soluble metal salts. After separation of the liquid fraction from the solid residue, iron is separated from the remaining metals in the liquid fraction by precipitation.

One disadvantage with conventional processes is that the hydrometallurgical leaching step involves dissolving all the metals to get valuable metals in to soluble form, which depends on the valuable metals associated with unwanted Fe/ any other metal. In such cases, load on purification of valuable metals leach solution increases and also loss some amount valuable metals occur. On the other hand, it is beneficial to manipulate leaching conditions to selectively leach valuable metals with higher recoveries. Clearly, it would be desirable from an economic standpoint to improve its recovery valuable metals as main usage of, corrosive chemicals, to fume generation during leaching, MOC benefits, cost of equipment, ease of handling of reagents, economically viable reagents/cheaper reagents.

CN 101818250B discloses a method for processing a cobalt-copper-iron alloy, which comprises the steps of pre-processing, first-stage leaching, second-stage leaching, and purifying and de-ironing with leaching solution by Water quenching autoclaving at high temperature & pressure to covert alloy into oxidic state followed by roasting at 1200 0 C , 10 hrs for activation. The method of the invention has a disadvantage as it is energy intensive operation- due to the usage of Autoclave reaction & rotary kiln. Further the Leach reside is subjected to magnetic separation and alloy is recycled to firing sequence in kiln. Cobalt recovery less it is about 90% only.

CN 101608258B discloses a method for industrially extracting cobalt, copper and iron by taking a cobalt-copper alloy as a raw material, which is characterized by comprising the following steps: (1) an oxidation leaching process, wherein water, concentrated sulfuric acid, concentrated nitric acid and a catalyst are prepared into mixed acid solution in a volume ratio of 10:0.5-6:0.5-6:0.1-10, and then a cobalt-copper alloy block is added to the mixed acid solution, so that the cobalt, the copper and the iron of the cobalt-copper alloy are leached into the solution; and (2) a solid-liquid separation process. Further the process covers mixed acid solution consisting water of Con. H2SO4, Conc. HNO3, Fluoride containing substance in the volume ratio of 10: 0.5 to 6:0.5 to 6:0.5 which is very corrosive in nature and difficult to handle in industries due to safety issues. The disclose process has a disadvantage wherein use of fluorine containing catalyst for catalytic action and an anti-passivation is used wherein Fluoride is hazardous and very corrosive.

US-3954448 describes a process for the recovery of cobalt from cobaltiferous materials. The process is mainly combining this process with copper smelting in order to treat intermediate products generated in hydro process. It is pyrometallurgic in nature, but the resulting alloy or matte is dissolved in the presence of copper sulfate. Copper cement precipitates, which is removed by means of filtration. The process disclosed in the patent includes Calcination at 600°C. The selective leaching of Iron, cobalt and/or copper from the alloy, and the recirculation of the cobalt sulfate to the leaching step, is not described. The method of the invention has a disadvantage as it is energy intensive operation- due to Calcination at 600°C and evaporation of mixed sulphate solution. Further Cobalt recovery less it is about 80% only.

CN 101086039 A describes a method for separating and recovering copper-cobalt alloy. It comprises the following steps: (1) milling and sieving copper-cobalt alloy; (2) leaching metal from alloy; (3) treatment for leach residue; (4) removing iron. CN 101086039 A describes a method wherein leaching metal from alloy is carried out by energy intensive step of pressure oxidation leaching. Further patent application CN 101086039 does not describe method for separating cobalt & copper and further their recovery process.

CN101463427B describes a method for recovering valuable metals from cobalt white alloy. The method comprises the following main steps: after the cobalt white alloy undergoes ball milling, chlorine and sulphuric acid solution are used for leaching; lixivium adopts N902 to extract copper, and bluestone is prepared after a copper-containing organic phase undergoes back extraction; extraction raffinate undergoes iron elimination by means of using amarillite, extraction and edulcoration by means of using P204, and then the separation of nickel and cobalt by means of using the N902; and cobalt chloride is prepared after a cobalt-containing organic phase undergoes back extraction. CN101463427Bdescribes a method for recovering valuable metals wherein process includes chlorine gas as an oxidizing agent in the process for leaching. The use of chlorine gas is hazardous, difficult in handling and corrosive. This makes the process difficulties at large scale for industrial use.

The present invention overcomes the above-mentioned problems of prior art processes for recovering valuable metals such as cobalt recovery from white alloy or alliageblanc or similar materials by two stage without pressure to convert cobalt & copper in to soluble form with a selective separation during leaching itself. Also process generates cobalt leached solution with very less amount of copper. This will help in avoiding extra processing step for removal of copper from cobalt solution.

SUMMARY OF INVENTION:
The main aspect of the present invention is a process of recovering of valuable metals such as cobalt and/or copper from white alloy/Alliageblanc comprises two stage leaching process in which the valuable metal is selectively leached such as cobalt and iron are leached in 1st and 2nd stage leaching process as soluble form. Residue generated from two stage cobalt leaching is mainly copper / copper cement. This copper cement is either sale directly to copper smelter or further leached for copper recovery. The residue from cobalt leaching is leached in acidic medium to convert copper to into soluble form followed by CuEW (copper electrowinning) to make copper metal/powder. Copper spent electrolyte (CuSE) so generated from CuEW is recycled back to copper leaching stage for utilizing free acid for leaching. The residue from copper leaching is very less quantity and being recycled back to leaching. Hence there is no residue generation from copper leaching. Recycling of CuSE is continuing till cobalt concentration reaches to approx. 10-15 gpl. After reaching cobalt concentration to 10-15 gpl, CuSE is transferred to cobalt leaching for cobalt recovery. Therefore, overall recovery of cobalt is 99.42 % & Copper is 98.76 % without residual material.

In one of the aspects of the present invention process of two stage leaching white alloy/Alliageblanc comprises leaching by treatment of white alloy/Alliageblanc with an aqueous, acidic solution under atmospheric pressure containing sulfate ion to form a soluble sulfate of the valuable metal contained in the white alloy/Alliageblanc. This leaching process in which the Cobalt and Iron contained in the white alloy/Alliageblanc is transiently forms soluble sulphates i.e CoSO4 and FeSO4. Leached solution is further processed for removal of iron either by atmospheric pressure or autoclave pressure. Further, the purified leach solution is either processed through solvent extraction followed by electrowinning steps to recover cobalt metal or precipitated out as a cobalt carbonate/cobalt hydroxide using lime, magnesium hydroxide, alkali by conventional process/methods etc. In second stage leaching cobalt is recovered by treating residue with sulphuric acid in presence of sodium metabisulphite, conc. nitric acid further followed by solid liquid separation. The filtrate generated is recycled to 1st stage cobalt leaching.

In another aspect, of the present invention provides a process for selectively extracting a valuable metal from white alloy/Alliageblanc.The process comprises the steps of: - pretreatment by powdering the alloy to particle size of less than 150µm; two stage leaching (cobalt leaching) of pretreated white alloy/Alliageblanc with sulfuric acid and oxidant addition in a mixed tank reactor equipped with means for feeding H2SO4, First stage thereby obtaining a sulfate of cobalt and iron as soluble sulphates [CoSO4 and FeSO4]. Leached solution is further processed for removal of iron either by atmospheric pressure or autoclave pressure. Cobalt metal is recovered from the purified leach solution by conventional process like solvent extraction followed by electrowinning or precipitating out as a cobalt carbonate/hydroxide using lime, magnesium hydroxide, alkali etc. Cobalt metal was recovered from the purified leach solution by solvent extraction by reacting purified leach solution with phosphoric acid organic reagent followed by phosphonic acid organic reagent to recover cobalt as cobalt metal or cobalt salts or precipitate to convert as cobalt products. The residue remains after 1st stage leaching was further treated with sulfuric acid, one reductant selected from the group consisting sodium metabisulphite or potassium metabisulphite and one oxidant selected from the group consisting of sodium hypochlorite or hydrogen peroxide or nitric acid in 2nd stage leaching. Further the solid residue obtained was treated again with sulphuric acid, one reductant selected from the group consisting sodium metabisulphite or potassium metabisulphite and one oxidant selected from the group consisting of sodium hypochlorite or hydrogen peroxide or nitric acid with a lesser dosage compared to 2nd stage cobalt leaching and higher acidity for recovery of copper and separation of copper metal containing in solid fraction.

According to another aspect of the present invention provides a process for selectively extracting a valuable metal from white alloy/Alliageblanc comprising:
(a) Pulverizing the alloy/Alliageblanc granules to about 100 to 300 mesh using vibrating mill/ melting and air or water atomized,
(b) Cobalt leaching:
1st stage: sulfuric acid with minimal free acid (pH: 1-1.5) for selective leaching of cobalt at 70-80 0 C
2nd stage: sulfuric acid with sodium metabisulphite or potassium metabisulphite and one oxidant selected from the group consisting of sodium hypochlorite or hydrogen peroxide or nitric acid at pH: 0.2-0.5
(c) Leached solution is further processed for removal of iron by atmospheric pressure or autoclave pressure,
(d) The purified leach solution from step (c) is treated for recovery of cobalt by 1st stage solvent extraction (SX) for impurities removal using phosphoric acid organic reagent followed by 2nd stage SX using phosphonic acid organic reagent to recover cobalt as high pure cobalt metal or cobalt salts or precipitate to convert as cobalt products in a conventional manner.
(e) the residue remain after cobalt recovery further treat with sulfuric acid (pH :0.2-0.5) to get higher metal recoveries at 70- 80 0 C, sodium metabisulphite or potassium metabisulphite and one oxidant selected from the group consisting of sodium hypochlorite or hydrogen peroxide or nitric acid at 70-80 0Ctemperature with a lesser dosage compared to 2nd stage cobalt leaching and higher acidity in copper leaching.
(f) The residue generated from copper leaching is recycled back in next batch of copper recovery.
(g) Copper spent electrolyte (CuSE) was recycled back to copper leaching till cobalt concentration reached to approximately 10-15 g/l, then transferred to cobalt leaching for production of cobalt recovery.
(h) The iron cakes generated from the iron removal step (c) is either sale or send to land filling site.

DETAILED DESCRIPTION OF FIGURE:
The invention will be better understood and the above objects as well as objects other than those set forth above will become more apparent after a study of the following detailed description thereof.

Figure 1: is a block flow diagram of a selective recovery of valuable metals from white alloy/Alliageblanc.

DETAILED DESCRIPTION OF THE INVENTION:
As used herein, the terms below have the meanings indicated.

The singular forms "a," "an," and "the" may refer to plural articles unless specifically stated otherwise.

The term "about," as used herein, is intended to qualify the numerical valuables which it modifies, denoting such a valuable as variable within a margin of error. When no particular margin of error, such as a standard deviation to a mean valuable given in a chart or table of data, is recited, the term "about" should be understood to mean that range which would encompass the recited valuable and the range which would be included by rounding up or down to that figure as well, taking into account significant figures.

As discussed above, the present invention is useful for extracting valuable metals from white alloys, Alliageblanc and similar raw material, which is produced by reduction of iron-rich oxidic ores operating at high temperature and in the presence of fluxes. These alloys typically contain for example about 30 to 75 percent by weight iron (Fe), about 10 to 40percent Cobalt (Co), about 10 to 50 percent Copper (Cu), about 1 to 10percent Silica (asSiO2), and about 1 to 10 percent phosphorous (P). Alloys typically contain little or no sulfur. These materials are sometimes referred to as "Alliageblanc" or “white alloy”.

In a particularly preferred embodiment, the process of the present invention is to recover cobalt and copper from a material which contains about 55 percent iron, 8 to 25 percent cobalt and about 20 to 30 percent copper.

Most of the metals in the white alloy or Alliageblanc, including iron and valuable metals, as cobalt and/or copper, having being reduced in the previous ore processing step. The first step in the preferred process of the present invention comprises selective two stage leaching cobalt from the alloy by an acidic leaching step conducted under oxidative conditions. In a preferred embodiment, acid is charged over a period of time into a reactor containing alloy slurry without applying pressure.

According to one of the embodiments of the present invention a method for selectively extracting a valuable metal from white alloy or Alliageblanc by two stage leaching metals using sulfuric acid with oxidant addition.

A preferred process for extracting valuable metals from a white alloy or alliageblanc or similar raw material will now be described below with reference to the flow diagrams shown in Figures 1.

According to one of the embodiments of the present invention provides a process for selectively extracting a valuable metal from white alloy/Alliageblanccomprising:
(a) Pulverizing the alloy/Alliageblanc granules to about 100 to 300 mesh using vibrating mill/ melting and air or water atomized,
(b) Co leaching:
1st stage: sulfuric acid with minimal free acid (pH: 1-1.5) for selective leaching of cobalt at 70-80 0 C. It reduces cost of chemicals for post processing (due to less acid)
2nd stage: sulfuric acid with one reductant selected from the group of sodium metabisulphite or potassium metabisulphite and one oxidant selected from the group consisting of sodium hypochlorite or hydrogen peroxide or nitric acid at pH: 0.2-0.5
(c) Leached solution is further processed for removal of iron by atmospheric pressure or autoclave pressure,
(d) The purified leach solution from step (c) is treated for recovery of cobalt by 1st stage solvent extraction (SX) for impurities removal using phosphoric acid organic reagent followed by 2nd stage SX using phosphonic acid organic reagent to recover cobalt as high pure cobalt metal or cobalt salts or precipitate to convert as cobalt products.
(e) the residue remain after cobalt recovery further treat with sulfuric acid (pH: 0.2-0.5) to get higher metal recoveries at 70- 80 0 C, one reductant selected from the group of sodium metabisulphite or potassium metabisulphite and one oxidant selected from the group consisting of sodium hypochlorite or hydrogen peroxide or nitric acid at 70-80 0 C temperature with a lesser dosage compared to 2nd stage cobalt leaching and higher acidity in copper leaching.
(f) The residue generated from copper leaching is recycled back in next batch of copper recovery.
(g) CuSE recycled back to copper leaching till cobalt concentration reached to approximately 10-15 g/l. After which CuSE is transferred to Cobalt leaching for production of cobalt recovery.
(h) The iron cake generated from the iron removal step (c) is either sale or send to land filling site.

In step (a) of the present invention white alloy or Alliageblancis pulverized /atomized less than 100 mesh to 300mesh (100µm to 200µm) size reducing it substantially to powdered form. The first step comprising powdering the alloy to particle size of about 100µm to 200µm by pulverizing the white alloy or Alliageblanc using vibrating mill/ melting and air/ or water atomized. Most preferably the white alloy is pulverized /atomized less 150 µm. The white alloy many also bepulverized /atomized in various other ways.

In step (b) of the present invention powdered white alloy is leached by two stage leaching. In the first stage leaching step wherein, valuable metals such as cobalt is leached to form soluble sulfates, CoSO4. The metallic iron present in the alloy is reacts with sulfuric acid in the leaching solution to form the soluble iron sulfates FeSO4. The pulverized /atomized white alloy or Alliageblanc having particle size less than 200 mesh size contains about by weight, 10 to 30% Cobalt (Co), 20 to 40 % Copper (Cu) and 30 to 50 % Iron (Fe). The pulverized /atomized white alloy or Alliageblanc is suspended and mixed in water. The slurry of suspended white alloy or Alliageblanc is heated to 30 - 1000C, and then treated with concentrated sulphuric acid by addition of sulphuric acid drop by drop and maintaining the pH between 1.0pH to 1.5 pH & temperature maintained between 50-1000C. The reaction mixture is also continuously monitored and as the cobalt & iron are leached into the solution the colour of solution becomes red, which indicates the dissolution of cobalt & iron into solution. The obtained slurry is filtered. The leached filtrate (382 mL) contains cobalt & iron as sulphates i.e. CoSO4 and FeSO4. The residue mainly contains copper and some parts of cobalt. The residue is transferred for 2nd stage leaching of cobalt.

In step (b) of the present invention for 2nd stage leaching of cobalt, the residue remain after cobalt recovery of 1st stage is treated with sulfuric acid (pH: 0.2-0.5) to get higher dissolution of metal at 70- 80 0 C and one oxidant selected from the group consisting of sodium hypochlorite or hydrogen peroxide or nitric acid as well as one reductant selected from group consisting ofsodium metabisulphite or potassium metabisulphite.

In step (c) of the present invention leached solution of step (b) is further processed for removal of iron by atmospheric pressure or autoclave pressure.
The iron sulfates in the leached solution immediately undergo disproportionation near to its hydrolysis pH in a single step, primarily forming hydrated iron oxide compound, iron hydroxide FeO (OH) and iron hydroxy sulfate Fe (OH)SO4, both of which are insoluble and further threated for the recovery of Iron. Loss of cobalt during iron removal step is very less (about <1%) in the present process. The iron is transiently dissolved during the first stage leaching step, but is immediately recovered on purification of the leached solution by atmospheric pressure or autoclave pressure.

The leached solution from first stage leaching for the recovery of iron by atmospheric pressure, Initial pH of the solution was 1.00 pH to 1.5pHandRedox potential is Eh +325 mv. The pH was adjusted & maintained to 2.5pH to 2.8pH by using calcium carbonate slurry (calcium carbonate to water ratio 1:1). The Redox potential Eh was maintained between +470 mv to +490 mv by adding hydrogen peroxide (50 % w/w) and pH maintained using calcium carbonate (slurry). The iron sulfates in the Leached solution immediately undergo disproportionation near to its hydrolysis pH forming hydrated iron oxide compound, iron hydroxide FeO (OH) and iron hydroxysulfate Fe (OH)SO4, which are insoluble and further treated for the recovery of iron. Solid and liquid are separated by filtration after completion of reaction time. The purified filtrate contains cobalt (Co) and iron (Fe)in very less quantity. The solid residue contains iron, and some amount of cobalt and Moisture.

In step (d) of the present invention the purified leach solution from step (c) is treated for recovery of cobalt by 1st stage solvent extraction (SX) for impurities removal using acids (such as phosphoric acid) in presences of organic reagent followed by 2nd stage solvent extraction using phosphonic acid organic reagent to recover cobalt as high pure cobalt metal or cobalt salts or precipitate to convert as cobalt products.

In step (e) of the present invention the residue remain in step (b) is transferred for 2nd stage leaching for recovery of cobalt. In 2nd stage leaching cobalt metal recovery further treat with sulfuric acid, sodium metabisulphite &oxidant selected from oxidant group i.e. hypochlorite or hydrogen peroxide or nitric acid or combination of two at 70-80 0 C temperature. The 1st stage leached residue was added in water, the slurry was heated to 50 to 60°C, in presence of reducing agent selected from the group consisting of sodium bisulfite and sodium metabisulfite, oxidant selected from the group consisting of hypochlorite or hydrogen peroxide or nitric acidwere added and pH maintained between 0.2pH to 0.5pH by adding conc. sulphuric acid drop by drop & temperature maintained between 70-800C. After the completion of reaction no more H2SO4 was consumed, indicating that the reaction has come to an end. The reaction mixture was filtered and solids and liquid were separated. The residue contains 2 to 6 % cobalt (Co), 60 to 80 % copper (Cu), 15 to 20 % iron(Fe) directly transfers for recovery of copper in 3rd stage or direct sale as cement copper or can be recycle back to smelting process for copper recovery, while the filtrate contains 5g/L to 10 g/LCopper (Cu), 8 g/L to 15 g/L Cobalt (Co) and 12 g/L to 20 g/L Iron (Fe).

The filtrate generated from 2nd stage leaching step is transferred to step (b) for separation and recovery of cobalt, iron, and copper. 2nd stage leach solution and water were added to pulverized /atomized less than 200 mesh size white alloy (solid to liquid ratio was 10 %). The alloy contains, by weight about 10 to 30% Cobalt (Co), 20 to 40 % Copper (Cu) and 30 to 50 % Iron (Fe). An overhead stirrer is used for suspending and mixing the alloy particles. As described in stage-1 as described in step (b) cobalt leaching same procedure followed for above recycle stage. Solids and liquid are separated by filtration. The leached filtrate contains 15 to 30g/L Co and 20 to 40 g/l Fe. The residue transferred for 2nd stage leaching of cobalt. The combined recovery after recycling 2nd stage solution obtained were 90 to 96 % Co, 0.1 to 0.2 % Cu &80 to 85% Fe. The separation of Cobalt and copper was achieved in this step. The cobalt recovery is increased to about 99.42 % after recycling of spent electrolyte generated from copper electrowinning (copper recovery). Thereby overall reagent consumption is reduced and therefore the process is economically viable. The process generated cobalt solution with negligible amount of copper, therefore separate copper removal processing step is not required before cobalt recovery.

In step (f) of the present invention is the 3rdstage leaching of the residue generated from 2nd stage leaching of resides of step (e) for recovery of copper. The 3rd leaching step is conducted under conditions in order to facilitate the copper leaching and generate soluble copper sulphate from the copper present in the solid phase. The 3rd leaching step is conducted on the residue remain after cobalt metal recovery. It is further treated with sulfuric acid(pH :0.2-0.5), one reductant from group consisting of sodium metabisulphite or potassium metabisulphite and one oxidant selected from the group consisting of sodium hypochlorite or hydrogen peroxide or nitric acid at 70-80 0 C temperature with a lesser dosage compared to 2nd stage cobalt leaching and higher acidity for copper recovery.

The 2nd stage leached residue is added to water/spent electrolyte (solid to liquid ratio was 10 %) and heated up to temperature of about 50-60 0 C and further conc. sulphuric acid was added drop wise till pH reaches to 0.2-0.5,
in presence of one reductant selected from the group consisting of sodium bisulphite and sodium metabisulfite and one oxidant selected from the group consisting of hypochlorite or hydrogen peroxide or nitric acid, pH is controlled between 0.2pH -0.5pH & temperature maintained 70-80 0 C. After completion of reaction no more sulphuric acid was consumed, indicating that the reaction has come to end. Further solid and liquids were separated by filtration.

The residue contains 1.4 % Co, 1.34 % Cu & 4.81 % Fe while the filtrate contains 62.29 g/l Cu, 1.51 g/l Co and 14.92 g/l Fe. The filtrate sent for recovering copper by electrowinning process & the spent electrolyte so generated contains cobalt (1.51 g/l) in the solution. Recycling this solution to copper leaching stage till it reaches to cobalt concentration (10-15 gpl). After recycling 10-15 gpl Co, CuSE is sent to cobalt leaching for cobalt recovery. Therefore, over all cobalt recovery was 99.42 % & copper recovery was 98.76 %.

In step (g) of the present invention the iron cakes generated from the iron removal step (c) is either sale or send to land filling site.

According to one of the embodiments of the present invention the powdered alloy is preferred for first leaching step wherein, valuable metals such as cobalt are oxidized and form soluble sulfates, CoSO4. The metallic iron present in the alloy is oxidized and reacts with sulfuric acid in the leaching solution to form the soluble iron sulphate, FeSO4.

This leached solution is further treated with oxidant and alkali to precipitate out iron by conventional process, Loss of cobalt during iron removal step is very less (about <1%) in the present process. The iron is transiently dissolved during the first leaching step, but is removed in purification of the leached solution by atmospheric pressure or autoclave pressure.

Under the leaching conditions used in the first leaching step of cobalt recovery, copper which is present in the alloy mostly in the form of copper metal is substantially unoxidized and unleached and remains in the solid phase. Therefore, the first leach effectively separates valuable metals such as cobalt and copper. The preferred conditions for the first leach are now discussed below.

The solution which forms the liquid fraction of the first leach is acidic, preferably containing sulfuric acid and having an initial pH no greater than about 1.5. More preferably, the leaching solution processed for removal of iron either by atmospheric pressure or autoclave pressure. The purified leach solution was treated for recovery of cobalt as mentioned below.

The liquid fraction is treated by direct solvent extraction using phosphoric acid organic reagent for impurities removal followed by extraction with phosphonic acid organic reagent to recover cobalt as cobalt metal or cobalt salts or precipitate to convert as cobalt products.

The inventors have found that performing a leaching step in two stages according to the preferred method described above results in substantially all the copper remaining in the solid phase with from about 70 % to about 95% of the valuable metals such as cobalt being extracted into the liquid phase. After completion of the leach, a solid/liquid separation is conducted to separate valuable metal-containing stream from the solid residue.

The leached solution from the process of the present invention provides a predominantly comprised of soluble salts, primarily sulfates, of valuable metals such as cobalt after recovery of iron. This purified leached solution is for Solvent extraction using phosphoric acid organic reagent, for recovery of cobalt from the purified leached solution, recovered cobalt as cobalt metal or cobalt salts or precipitate to convert as cobalt.

The second leaching step is conducted under reductive -oxidative conditions in order to facilitate dissolution of all of cobalt metal and some iron present in the residue of first stage leaching. It is further treated with sulfuric acid, one reductant selected from group of sodium metabisulphite or potassium metabisulphite and one oxidant selected from the group consisting of sodium hypochlorite or hydrogen peroxide or nitric acid at pH: 0.2-0.5 and temperature between 70-80 0 C.

The residue generated from the 2nd stage leaching contains significant amount of copper and is further processed to recover copper.

The object of the second stage leaching is to extract the remaining cobalt un-extracted in the first leach. As in the two-stage leaching process, the white alloy or Alliageblanc is treated with an acidic leaching liquid which contains sulfuric acid. The initial pH of the leaching liquid is typically less than about 2.0 pH, more typically about 1.4 pH, reflecting the sulfuric acid content of the leaching liquid. After addition of the solid residue to the leaching liquid, the pH may increase to about 2.5 pH to 5.0 pH, but decreases during the second leach to about 1.4 pH to 1.6 pH, reflecting the liberation of H2SO4 during the formation of insoluble iron compounds.

The liquid phase or filtrate from the 2nd stage leaching is recycled to the first stage leaching for the recovery of cobalt. The cobalt leached solution is treated to remove iron into the solid phase and cobalt is remains in liquid phase as cobalt sulphate. The purified leached solution is treated for recovery of cobalt by solvent extraction (SX) for impurities removal using phosphoric acid organic reagent followed by 2nd stage SX using phosphonic acid organic reagent to recover cobalt as high pure cobalt metal or cobalt salts or precipitate to convert as cobalt products.

The 3rd leaching step is also conducted under reductive-oxidative conditions in order to facilitate oxidation of the all of copper metal present in the solid phase from the 2nd stage leaching. It is further treated with sulfuric acid, one oxidant selected for the group consisting of hypochlorite or hydrogen peroxide or nitric acid as well with reducing agent selected for the group consisting of sodium metabisulphite or potassium bisulphite at pH is controlled between 0.2-0.5 and temperature between 70-80°C.

In addition to extraction of copper from the solid phase, the 3rd leaching step also is useful for removing any residual valuable metals remaining in the solid residue after the first and second leach. These valuable metals may be entrained in the solid residue in the form of soluble sulfates, or in the form of insoluble compounds such as hydroxysulfates or metallics. These compounds are converted in the 3rd leaching step to soluble sulfates, such as copper sulfate, and are extracted into the liquid phase during the 3rd leaching step.

After the completion of the all stage leaching process, a solid/liquid separation is conducted in order to separate the cobalt containing in liquid phase, which may also contain some other valuable metals and solid residue. As in the leaching process, the selective leaching of the metals for the separation is preferably accomplished. In order to remove soluble Iron and cobalt compounds from the solid residue as completely as possible, the solid residue is preferably separated from the first and second stage leaching process.

In preferred embodiments after the complication of the first and second stage of leaching, the solid residue contains copper is leached to recover copper as soluble copper sulfates. Further the liquid spent electrolyte from copper electrowinning is recycled to use free acid of copper spent electrolyte. The liquid spent is collected as recycled bleed of solution which contain about 10-15 g/l cobalt from different batch of copper leaching process. The bleed liquid spent form copper leaching process after leaching the solid residue is recycled back to cobalt leaching stage for further cobalt recovery. Therefore, there is no residue generated/left from the process. Further all cobalt is ultimately recycled to cobalt leaching stage for cobalt recovery.

The temperature of the acidic leaching solution is preferably maintained at an average temperature of less than about 100°C during the leach in order to avoid oxidizing copper cement to soluble copper sulfates. More preferably, the temperature is maintained in a range of from about 65 to about 100°C, and even more preferably from about 75 to 85°C.

The present invention is further illustrated by the following examples.

EXAMPLE 1
A white alloy 200 g was pulverized into a particle size ranging of less than 200 mesh size by using vibrating mill/ air or water atomizer.
A. Co leaching

Stage-1
Take 600 ml glass beaker, add 400 ml water & add 40 g of pulverized /atomized less than 200 mesh size white alloy (liquid to solid ratio was 10 :1). The alloy contains, by weight, 23.36 % Co, 29.23 % Cu and 36.36 % Iron. An overhead stirrer is used for suspending and mixing the alloy particles. The slurry is heated to 50-600C, then concentrated sulphuric acid was added slowly drop by drop for maintaining the pH kept between 1.0 - 1.5 & temperature maintained between 70-800C. The reaction mixture is also continuously monitored. The colour of solution becomes red, which indicates the dissolution of cobalt & iron into solution. After 3 hrs, the leaching comes to an end, as indicated by the constant pH 1.0-1.5. The obtained slurry is filtered. The leached filtrate (382 mL) contains 18.61 g/L Co and 23.84 g/l Fe, 0.042 g/l Cu. The residue (21.0 g) transferred for 2nd stage leaching of cobalt.

Stage-2
In 400 ml glass beaker, 200 ml fresh water added (liquid to solid ratio was 10 :1) & 1st stage leached residue was added, the slurry heated to 50 to 60°C, 4 gm sodium metabisulphite, 3 ml con. nitric acid was added and pH maintained between 0.2-0.5 by adding conc. sulphuric acid drop by drop & temperature maintained between 70-800C. After 3 hrs, no more H2SO4 was consumed, indicating that the reaction has come to an end. Solids and liquid are separated by filtration. The residue (13.3 grams) contains 4.02 % Co, 75.64 % Cu, 17.98 % Fe directly transfers for recovery of copper in 3rd stage or direct sale as cement copper or can be recycle back to smelting process for copper recovery, while the filtrate (190 mL) contains 8.32 g/L Cu, 10.21 g/L Co and 15.88 g/L Fe.
Stage-1 Recycle
Take 600 ml glass beaker, add 2nd stage leach solution (190ml) and water (210ml) & add 40 g of pulverized /atomized less than 200 mesh size white alloy (liquid to solid ratio was 10 :1). The alloy contains, by weight, 23.36 % Co, 29.23 % Cu and 36.36 % Iron. An overhead stirrer is used for suspending and mixing the alloy particles. As described in stage-1 cobalt leaching same procedure followed for above recycle stage. Solids and liquid are separated by filtration. The leached filtrate (382 mL) contains 18.61 g/L Co and 23.84 g/l Fe, 0.042 g/l Cu. The residue (21.5 g) transferred for 2nd stage leaching of cobalt. The combined recovery after recycling 2nd stage solution obtained were96.84 % Co, 0.14 % Cu &83.36% Fe. Excellent separation of cobalt and copper was achieved in this step. Also, while recovering cobalt iron leaching is only 83.36 % which is less compared to convention vigorous leaching process. However overall cobalt recovery increased to 99.42% after recycling of spent electrolyte generated from copper electrowinning (copper recovery). Overall reagent consumed is very less and therefore the process is economically viable. This will help also to minimise hydrogen gas evolution during leaching.

Iron Purification
The leached solution from recycle step (250 mL) was processed for removal of iron by atmospheric pressure, Initial pH of the solution was 1.01 & Eh +325 mv, so pH adjusted & maintained to 2.5-2.8 by using calcium carbonate slurry (calcium carbonate to water ratio 1:1) for 1 hr. Then Eh maintained between + 470 mv to + 490 mv by adding hydrogen peroxide (50 % w/w) and pH maintained using calcium carbonate (slurry) for 2 hrs. Solid and liquid are separated by filtration after completion of reaction time. The solid residue repulped in water (ratio of cake to water as 1:1.5). The purified filtrate (352 mL) contains 13.15 g/L Co and 0.021 g/l Fe. The solid residue (202 g) contains 4.96 % Fe, 0.019% Co, and 65% Moisture. The cobalt loss is very less.

B. Cu leaching
Stage-3
Take 150 ml fresh water/spent electrolyte in a 400 ml glass beaker (solid to liquid ratio was 10 %) & 2nd stage leached residue is added, the slurry was heated to 50-600C, conc. sulphuric added drop by drop, sodium metabisulphite (2 g), conc. Nitric acid (1.5ml) are added and pH is controlled between 0.2-0.5 & temperature maintained 70-80 0 C. After 3 hrs, no more sulphuric acid was consumed, indicating that the reaction has come to end. Solid & liquid are separated by filtration. The residue (3.10 g) contains 1.4 % Co, 1.34 % Cu & 4.81 % Fe while the filtrate (160 ml) contains 62.29 g/l Cu, 1.51 g/l Co and 14.92 g/l Fe. The filtrate sent for recovering copper by electrowinning process (CuEW)& the spent electrolyte (CuSE) so generated contains cobalt (1.51 g/l) in the solution. Recycling this solution to copper leaching stage till it reaches to cobalt concentration (10-15 gpl). After that it is sent to cobalt leaching for recovery cobalt.

Therefore, over all cobalt recovery was 99.42% and copper recovery was 98.76%.

The residue (3.10grams) contains 1.4 % Co, 1.34 % Cu and 4.81 % Fe, while the filtrate (160mL) contains 62.29 g/L Cu, 1.51 g/L Co and 14.92 g/L Fe.Residue can be recycled again to copper leaching for further recovering valuable metals. Hence there is no leftover residue generation in the process.

Recovery Table 1

EXAMPLE 2
Alliage Composition
Elements Cobalt, % Copper, % Iron, %
Alliage -1 23.36 29.23 36.36
Alliage -2 19.67 29.87 42.21

Leaching Conditions-1st stage (Cobalt leaching)
1 Input RM, g 40gm
2 PD, % 10%
3 pH 1.1-1.5
4 Temperature, °C 70-80°C
5 Reaction time, hrs 3hrs
6 Conc. Sulfuric acid as per conditions

Leaching Conditions-2nd stage (Cobalt leaching)
1 1st stage Cake, g 20gm
2 PD, % 10%
3 pH 0.2-0.5
4 Temperature, °C 70-80°C
5 Reaction time, hrs 3hrs
6 Conc. Sulfuric acid as per conditions
7 Sodium metabisulphite,g 4gm
8 Con. Nitric acid, ml 3ml

Leaching Conditions-3rd stage (copper leaching)
1 Cemented copper 20gm
2 PD, % 10%
3 pH 0.2-0.5
4 Temperature, °C 70-80°C
5 Reaction time, hrs 3hrs
6 Conc. Sulfuric acid as per conditions
7 Sodium metabisulphite,g 2gm
8 Con. Nitric acid, ml 1.5ml

Leaching Recovery - 1st stage & 2nd stage (Cobalt leaching)
TEST NO Co Recovery, % Fe Recovery, %
Example-1 96.84 83.36
Example-2 96.59 81.18
Example-3 94.59 90.00

Leaching Recovery -3rd stage (Copper Leaching)
TEST NO Cu Recovery, % Fe Recovery, % Co Recovery, %
Example-1 98.76 16.41 2.586
Example-2 98.47 16.06 2.609
Example-3 98.08 9.90 4.472