Cross Reference to Related Applications

[0001] The present application claims the benefit of U.S. Application No. 63,408,533 filed September 21 , 2022, being incorporated herein by reference in its entirety for all purposes.

Technical Field

[0002] The present invention relates to a process for using a mixture of CO and H2 to reduce and precipitate copper in primary copper refining.

Background

[0003] Copper powder was produced using reduction gases in back end purification processes. There have been some industrial applications of the gas based reduction approaches to produce copper powder from ammoniacal and sulfate leaching media.

[0004] Below are some examples of methods have been used to reduce and precipitate copper in primary copper extraction industry using CO and/or H2.

[0005] Evans et al. disclose (Evans et al. "Production of copper powder by hydrogen reduction techniques", Can Min Metal Bull 54.591 (1961 ): 530-538) a pilot scale production of copper powder. The process started off with air and ammonia assisted leaching of copper concentrates at 100 psig total pressure and 200°F, then extended to precursor mixtures containing 0.5% Cu, 29.7% S and 31.2% Fe: Pentalindite (Fe, Ni, S), chalcopyrite (CuFeS2). The produced copper powder was dried in the hydrogen atmosphere before packaging.

[0006] Joe O’Connor (Joe O’Connor, Chemical Engineering, 1952, p164-168) discloses chemical refining of metals extending the process to recover copper from copper and brass copper to extract metallic copper from sulfidic float concentrates, in which high pressures and high temperatures have been harnessed.

[0007] Yurko, W. J. discloses ("Refining copper by acid leaching and hydrometallurgy." Chem. Eng 73.18 (1966): 64-66) refining copper by acid leaching and hydrometallurgy. More specifically, Yurko discloses hydrogen reduction of acidic copper sulfate solutions from impure precipitates yields high-purity copper while regenerating sulfuric acid.

[0008] Peters et al. disclose ("A carbonyl-hydrometallurgy method for refining copper." mmij-aime papers, May 24-27, 1972, Tokyo) a use of CO in the refining of copper. Carbonyl assisted refining is suitable for copper precursors in the form of powder, tailings or granulated.

Extraction: CuSO4<aq) + Cu (impure) + 2CO<g) = (Cu(CO))2SO4<aq) (1 ) Depressurization: (Cu(CO))2SO4<aq) = Cu ₂ SO4(aq) + 2CO< _g ) (2) Disproportionation: CU2SO4 (aq) = Cu (pure) + CuSO4<aq) (3)

[0009] Stenhouse discloses (Stenhouse, Joanne Helen, “Reduction of aqueous cupric sulfate by hydrogen, carbon monoxide, and their mixtures”, A thesis for the degree of master of science, University of British Columbia, 1982) reduction of aqueous cupric sulfate by hydrogen, carbon monoxide, and their mixtures. The effect of increasing the copper sulfate concentration was to enhance the rate of reduction in both the hydrogen and carbon monoxide systems. The rate of reduction was increased by increasing pressure, temperature, and the concentration of ammonium sulfate buffer. Under mixtures of H ₂ and CO the rate of the reduction was intermediate between the rate under pure H ₂ and pure CO.

[0010] Chemical Construction Corporation was a builder of natural gas plants for government and defense contracts and has many granted patents regarding the use of Hydrogen, Carbon Monoxide and Ammonia for the precipitation of copper in sulfate and ammonia media.

[0011] GB 691 ,1 15 discloses copper bearing and iron bearing minerals are treated to convert copper into copper sulfate. A challenge in the production of copper included the production of a very high purity of copper (> 99.9%). The process claims to treat copper and iron bearing materials not limited to sulfides and oxides with the addition of sulfuric acid with some copper content. Ferrous sulfate is separated in the filtrate and copper is precipitated as copper sulfide. The copper sulfide residue is enriched to convert it into a soluble copper salt. The process claim is also extended to an oxidative treatment of slurry with air/Oxygen. The copper sulfide precipitate cake is subjected to an exothermic reaction with Oxygen to convert insoluble sulfides to soluble sulfates at a temperature less than 325°C. The cupric ions are reduced to cuprous with the help of CO gas flowing in. The leached solution saturated with CO is then passed through a continuous autoclave at 100 to 150 psig CO pressure at a temperature regime of 200°C to 275°C. The authors suggest operating at 60 to 70% theoretical precipitation throughput to obtain a 99.9% pure copper precipitate.

[0012] GB691 ,113 discloses a process of precipitating the copper to produce very high purity. Precipitation is carried out on copper solutions constituting copper mine waters, ammoniacal or carbonate leaching of ore or secondary scrap materials, acid leaching of oxide, carbonate or sulfide ores. Copper of electrolytic grade (99.9%) pure can be formed. The leached solution is saturated with CO at 110°C- 150°C if ammoniacal solution is used for leaching, 150°C-300°C if sulfuric acid is used as a leaching media. The saturated solution is precipitated in an autoclave at temperatures between 200°C - 250°C at a pressure of 300 - 700 psig for sufficient time to precipitate 99.9% pure copper recovered at 60 - 75% recovery.

[0013] GB 699,303 discloses an extraction of copper from copper bearing scrap with the addition of ammoniacal copper carbonate. Residual copper content after precipitating the copper powder is recycled. The solution to be treated will be containing a maximum of 110 g/L Cu. The reducing gas used for the study is not limited to CO and contains H ₂ at a temperature regime of 350°F- 500°F. Partial pressure ratios of CO and H ₂ were not provided.

[0014] GB 770, 112 discloses a precursor liquid to be used forthe reduction process extends to leaching of ores containing copper and at least one non-ferrous metal, usually nickel and or cobalt. Reduction is carried out in a pH regime less than 6.5 preferably between 3-4 by adjusting the free acid content to less than 20% and a buffer of ammonium sulfate to initiate selective leaching of copperv/s nickel or cobalt. Copper solutions containing less than 10 g/l copper are not used. Temperature of reduction was around 275°F at a finite pressure of reducing gas and a total pressure preventing boiling (600 - 900 psi). Reducing gas is selected from a group consisting of hydrogen, carbon monoxide and mixtures thereof.

[0015] GB 269,164 discloses the use of reducing gases CO and H ₂ for the reduction of heavy metals from ammoniacal leach liquors at elevated temperatures and pressures. Reduction time, operating pressure and temperature dictate the purity of obtained precipitate. The patent claims to expand to heavy metals especially copper, use of CO and H ₂ and corresponding mixtures for reduction. No ranges of temperatures, pressure and reduction times were provided.

[0016] GB 1252065 discloses extracting copper powders from ammoniacal leach solutions, a process extended to sulfate leach solutions from ores. Copper concentration in aqueous solution can range from 1 g/L to 30 g/L, Nickel is 1 to 150 g/L. CO can be used is pure CO or producer gas (CO+H2); H2 is not claimed for. The total pressure of CO used is 200 psig to 1200 psig at temperatures from 100°C to 250°C. The patent also claims the use of finely divided copper as seed material (0.01 - 0.1 g/l).

Summary

[0017] There is disclosed a process for reducing and precipitating copper in primary copper extraction, the process comprising: adding a gas mixture of CO and H2 to a solution of CuSO4 forming a copper carbonyl (Cu(CO))2SO4; depressurizing the solution to decompose the copper carbonyl (Cu(CO))2SO4 to CU2SO4 and CO; disproportioning Cuprous sulfate to form Copper powder and Cupric sulfate; and precipitating the copper as a copper powder, wherein CO in the mixture of CO and H ₂ ranges from 50% to 90%(v/v).

[0018] In some embodiments, CO is 75% in the mixture of CO and H2.

[0019] In some embodiments, a reaction temperature ranges from 150 to 240°C.

[0020] In some embodiments, a reaction temperature ranges from 180 to 190°C.

[0021] In some embodiments, a reaction temperature is 185°C.

[0022] In some embodiments, a reaction pressure ranges from 400 to 1000 psig.

[0023] In some embodiments, a reaction pressure ranges from 500 psig to 700 psig.

[0024] In some embodiments, a reaction pressure is 600 psig.

[0025] In some embodiments, a copper content in the solution ranges from 40 to

50 g/L.

[0026] In some embodiments, H2SO4 ranges 120-240 g/L in the solution.

[0027] In some embodiments, H2SO4 is 150 g/L in the solution.

[0028] In some embodiments, FeSC ranges from 1 to 10 g/L in the solution.

[0029] In some embodiments, FeSC is free in the solution.

[0030] In some embodiments, a purity of the copper powder is 99.9%.

[0031] In some embodiments, no ammonium sulfate is added. Brief Description of the Drawing

[0032] For a further understanding of the nature and objects of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

FIG. 1 is cuprous concentration and total copper concentration in pregnant leach solution with calibration experiments; 0.7 M copper sulfate, 0.6 M ammonium sulfate and 0.1 M sulfuric acid. Conditions used were 150°C, 4 h of leaching time, pCO/pH ₂ = 2/1 ;

FIG. 2 is free acid concentrations (g/L) in pregnant leach solution with calibration experiments; 0.7 M copper sulfate, 0.6 M ammonium sulfate and 0.1 M sulfuric acid. Conditions used were 150°C, 4 h of leaching time, pCO/pH2= 2/1 ;

FIG. 3 is ORP (mv) of reduced solutions collected from autoclave with calibration experiments;

FIG. 4 is cuprous in solution High acid experiments, 150°C;

FIG. 5 is off gas analysis of gases extracted from autoclave in solution High acid experiments, 150°C;

FIG. 6a is cuprous (g/l) in experiments with high acid at 170°C;

FIG. 6b is cuprous (g/l) in experiments with high acid at 170°C;

FIG. 7a is gas analysis of off gas, atmosphere of autoclave with high acid at 170°C;

FIG. 7b is another gas analysis of off gas, atmosphere of autoclave with high acid at 170°C;

FIG. 8 is cuprous concentration in pregnant leach solution with high acid at high temperature 180°C and 190°C;

FIG. 9 is free acid concentration (g/L) in pregnant leach solution with high acid at high temperature 180°C and 190°C;

FIG. 10 is ORP (mv) of reduced solutions collected from autoclave with high acid at high temperature 180°C and 190°C;

FIG. 11 is cuprous in solution in experiments with varying CO% in feed: 73% CO, 27% H ₂ ;

FIG. 12 is free acid in solution in experiments with varying CO% in feed' 73% CO, 27% H ₂ ; FIG. 13 is cuprous (g/l) in experiments with varying CO% in feed: higher% CO (75%, 80%) in feed syngas;

FIG. 14 is free acid (g/l) in experiments with varying C0% in feed: higher% CO (75%, 80%) in feed syngas;

FIG. 15 is ORP (mv) in the experiments v/s time with varying C0% in feed: higher% CO (75%, 80%) in feed syngas;

FIG. 16 is cuprous (g/l) in experiments with two different rich electrolyte solutions: Acid Variation;

FIG. 17 is free acid (g/l) in experiments with two different rich electrolyte solutions: Acid Variation;

FIG. 18 is ORP (mv) in the experiments v/s time with two different rich electrolyte solutions: Acid Variation;

FIG. 19 is cuprous (g/l) in experiments with two different rich electrolyte solutions: Acid Variation with Ferrous;

FIG. 20 is free acid (g/l) in experiments with two different rich electrolyte solutions: Acid Variation with Ferrous;

FIG. 21 is ORP (mv) in the experiments v/s time with two different rich electrolyte solutions: Acid Variation with Ferrous; and

FIG. 22 is a flowchart of an exemplary embodiment of a process for carbonyl based refining of copper according to the disclosed method.

Description of Preferred Embodiments

[0033] Disclosed are method of gas based reduction of copper in primary copper refining. More specifically, the disclosed methods relate to a process for using a mixture of CO + H2 syngas to reduce and precipitate copper in primary copper extractions, which relates to carbonyl based refining of copper. The disclosed methods may be implemented on rich electrolytes exiting a solvent extraction circuit in primary copper hydrometallurgy operations. The benefits of using the mixed gas (i.e., CO + H2) for precipitation of copper include a better control of parameters that affect the process, such as temperature, reaction time, total pressure, partial pressure ratio of CO and H ₂ (pCO/pH2). The disclosed method may achieve a total 80% of theoretical copper recovery that is close to the theoretical copper recovery, at a high purity > 99% of copper powder, such as, 99.9% purity. Here the theoretical copper recovery is 50% according to Equations (4) and (6) below. A total 80% of theoretical copper recovery is 80% x 50%.

[0034] It has been known primary extraction of copper dominates a copper value supply chain. Pyrometallurgical and hydrometallurgical processes account for 80% and 20%, respectively, of the primary copper share. The final refining step for copper extraction (primary and secondary recycling) processes utilize electricity: electrorefining for pyrometallurgy (primary and secondary) and electrowinning for hydrometallurgy. Very low current densities (300 A/m ² - 500 A/m ² ) leading to large capital cost for electrochemical cells and energy costs experienced in electrowinning operations account for increased production costs. The CAPEX (30% total CAPEX) and OPEX intensive electrowinning operations have been a bottleneck for expansive implementation of hydrometallurgy based primary copper extraction processes.

[0035] The disclosed methods explore the possibility of using CO + H2 to reduce copper in solvent extraction (SX) rich electrolytes to Copper powder. The disclosed methods is believed to reduce the cost of copper by 20% comparing to the cost of copper produced by electrowinning owing to high energy requirements in electrowinning.

[0036] The disclosed methods of gas based reduction of copper/carbonyl refining of copper is able to treat rich electrolytes emanating from a solvent extraction circuit using the syngas CO + H2.

[0037] The advantages of the disclosed methods include: i) the disclosed methods are able to treat high copper in solution with high acid content Cu (> 40 g/L) as cuprous sulfate and sulfuric acid (> 120 g/L) in a rich electrolyte, and ii) the disclosed methods are able to tolerate high amounts of Fe (from 1 to 10 g/L) as ferrous sulfate in solution.

[0038] FIG. 22 is a flowchart of an exemplary embodiment of a process for carbonyl based refining of copper according to the disclosed method. At step 102, the syngas, CO + H2, is synthesized from a syngas mixing station. First, CO and H2 gas lines are prepared and both lines are under 1000 psig pressure on delivery gauges. A mass flow meter is connected to each of the two gas lines and when switching on the mass flow meters, the two gases, CO and H2, are mixed in the syngas mixing station. Here, CO and H2 gases each has a purity of 99.99% from a gas cylinder. At step 104, a desired quantity of cupric, iron salts and sulfuric acid solution is loaded into a pressure autoclave and the syngas CO and H2 from the syngas mixing station is also fed into the pressure autoclave. Cupric sulfate CUSO4 is formed in the cupric, iron salts and sulfuric acid solution. Copper reduction reaction occurs in the pressure autoclave once the cupric, iron salts and sulfuric acid solution and the syngas CO and FF are loaded into the pressure autoclave. Equations (4) - (6) below represent the possible reaction mechanism involved in the pressure autoclave. The copper reduction reaction is usually conducted in the pressure autoclaves, to form a stable cuprous carbonyl complex (Cu(CO))2SO4. At step 106, The cuprous carbonyl (Cu(CO))2SO4 is then depressurized to form cuprous sulfate CU2SO4 which later disproportionates (step 108) to form copper metal powder and cupric sulfate in an atmospheric reactor. Simultaneously, CO is generated. The cuprous sulfate CU2SO4 is recycled back to the pressure autoclave for reduction and CO is recycled back to the syngas mixing station as CO feed. H2SO4 generated from the reduction reaction is also recycled back to the pressure autoclave. Stoichiometry theoretical maximum of copper recovery or precipitated is 50% of cupric sulfate (Cu ⁺² ) input according to reaction Equations (4) to (6), that is, 2 moles of copper as cupric sulfate in solution produce a maximum of 1 mole of copper as powder by reduction with CO and H2.

Reduction: 2CuSO4(aq) + 2CO(g)+ H2 (g) - (Cu(CO))2SO4(aq) + H2SO4(aq) (4)

Depressurization: (Cu(CO))2SO4(aq) = Cu ₂ SO4(aq) + 200® (5)

Disproportionation: CU2SO4 (aq) = Cu (pure) + CuSO4<aq) (6)

[0039] Afterward, liquid samples from the pressure autoclave are collected with a liquid sample vial in a period, such as 30 minute time intervals. This process may be accomplished using a 10 ml bomb sampler. The liquid sample vial is flushed with N2 prior to sample collection. The collected liquid sample is then filtered and collected. The liquids and solids from the liquid sample are stored. Repeat this process of the sample collection for kinetic samples at certain time intervals, for example, at 30 min intervals. After that, gas sample is collected and analyzed. Gas from the pressure autoclave headspace is used to analyze the gas composition right after the liquid sample is collected. At the end of the experiment, the remainder of the solution in the autoclave is collected under vacuum and ejected into a 2 L glass reactor to conduct the controlled precipitation of copper under N2/steam sparging. A total 80% of theoretical copper recovery that is close to the theoretical copper recovery, at a high purity > 99% of copper powder, such as, 99.9% purity may be achieved.

[0040] The disclosed methods may be conducted at a temperature greater than 150°C. Preferably, the temperature ranges from 150°C to 190°C, more preferably, the temperature being about 185°C. [0041] The disclosed methods may be conducted at a pressure ranging from 400 psig to 1000 psig, preferably, the pressure ranging from 500 psig to 700 psig, more preferably, the pressure being around 600 psig.

[0042] Synthetic rich electrolytes of the disclosed methods are prepared at specific concentrations of cupric or copper (source copper sulfate) and sulfuric acid. For example, cupric concentration may range from 30 g/L to 80 g/L (i.e., Cu content in cupric); H2SO4 concentration may range from 120 g/L to 240 g/L; FeSC>4 concentration may range from 1 to 10 g/L (Fe content in FeSO4); ammonium sulfate concentration may range from 0.2 to 1 M if any. Here a hastealloy based autoclave may be used as the pressure autoclave owing to intactness during reducing conditions. The disclosed methods consist of an autoclave to conduct reduction and a gas cleaning and scrubbing. A syngas station may be used to supply a specific composition of syngas, such as CO and H2, at a required pressure. Periodic sampling, e.g., periodic liquid sample collection, may be conducted in a triple vacuum plus N2 purged bomb sampler, the contents of the bomb sampler are taken to a glovebox for further analysis. Here the triple vacuum plus N2 means 3 cycles of vacuum plus N2 purging. That is, the bomb sampler is purged with N2 and then vacuumed in a cycle. This cycle is conducted 3 times.

[0043] In some embodiments, the disclosed methods include various chemical assays that may be performed on liquid, solid and gas samples generated in the experiments. The liquid samples collected from the autoclave are sparged in N2 to hasten the disproportionation process.

[0044] In some embodiments, the disclosed methods include Cuprous Titration performed on unsparged sample from autoclave. Solution may be mixed with Ferric solution. The resulting ferrous solution mixture is titrated with Cerric solution. The amount of cuprous is then calculated.

[0045] In some embodiments, the disclosed methods include Free Acid titration performed on sparged samples. The samples may be buffered with CioHi2MgN2Na20s (Mg-EDTA) and MgCh. The buffered solution is titrated with 0.1 M NaOH to give the free acid concentration.

[0046] In some embodiments, the disclosed methods include gas analysis analyzed in a period, such as, every 60 mins in an Infrared (I R)/ Thermal Conductivity detector (I R/TCD).

[0047] In some embodiments, the disclosed methods include Copper concentration (mg/l) analysis. Microwave Plasma - Atomic Emission Spectroscopy (MP-AES) is used to analyze the concentration of copper in the solution.

[0048] In some embodiments, the disclosed methods include copper purity analysis. That is, solid analysis compared with pure copper metal.

[0049] The advantages of the disclosed methods include, but are not limited to,

• Gas based reduction of copper and/or carbonyl refining of copper capable of treating rich electrolytes emanating from a solvent extraction circuit by using a syngas of CO and H2;

• The disclosed methods are capable of treating high copper (i.e., copper concentration ranging from 20 g/L to 80 g/L) in solution with high acid content (i.e., sulfuric acid concentration ranging from 100 g/L to 220 g/L);

• The disclosed methods are able to tolerate high amounts of Fe (e.g., 1 to 10 g/L) as Ferrous sulfate in solution;

• The disclosed methods do not require a specific free acid concentration to precipitate copper from rich electrolytes/cuprous sulfate; also don't need ammonium ions as part of the solution to speed up kinetics.

• The disclosed methods disclose the optimal CO/H2 ratio needed for the reduction; and

• The disclosed methods are capable of producing copper powder having a purity of 99.9%.

Examples

[0050] The following non-limiting examples are provided to further illustrate embodiments of the invention. However, the examples are not intended to be all inclusive and are not intended to limit the scope of the inventions described herein.

Experimental Setups:

[0051] Reduction and syngas production: The experiment was conducted at high temperatures (i.e., > 150°C) and high pressures (i.e., 400 psig - 800 psig). Synthetic rich electrolytes were prepared in the laboratory at a specific concentration of Copper (source copper sulfate) and sulfuric acid. Haste alloy based autoclave was used owing to intactness during reducing conditions. The experimental set up consists of autoclave to conduct reduction and a gas cleaning and scrubbing set up. Syngas station was used to supply a specific composition of syngas (e.g., CO/H2) at a required pressure. Periodic sampling was conducted in a triple Vacuum and N2 purged bomb sampler, the contents of the bomb sampler were taken to a glovebox located forfurther analysis.

[0052] Chemical Assays: Various chemical assays were performed on the liquids, solids and gas samples generated in the experiments. The liquid samples collected from the autoclave were sparged in N2 to hasten the disproportionation process.

• Cuprous Titration: Performed on unsparged sample from autoclave. Solution mixed with Ferric solution, the resulting ferrous solution was titrated with Cerric solution. The amount of cuprous was then back calculated.

• Free Acid titration: Performed on spareged sample. Sample was buffered with Mg-EDTA and MgCl2. The buffered solution was titrated with 0.1 M NaOH to give the free acid concentration.

• Gas analysis: Analyzed every 60 mins in an IR/TCD detector.

• Copper (mg/l) analysis: MP-AES was used to analyze the concentration of Copper in the solution.

• Copper purity analysis: Solid analysis Compared with pure Copper metal. Work in progress to quantify the impurities present in the sample.

[0053] Five compositions of rich electrolytes were experimented with varying temperature, pCO/pH2, time.

Example 1 . Calibration experiments

[0054] Calibration experiments (i.e., CC 11 , CC 12, CC 13 and CC 14) were performed on 0.7 M copper sulfate, 0.6 M ammonium sulfate and 0.1 M sulfuric acid. Conditions used were 150°C, 4 h of leaching time, pCO/pH2= 2/1 and agitation used was 1100 rpm. Results are shown in FIG. 1 to FIG. 3. The calibration experiments were successful in the extraction of copper powder & hinting at the mechanism of the formation of cuprous carbonyl. The data was replicable and the analysis was able to cite the direction of the reaction. A gradual increase in the free acid concentration concurrent to the stoichiometry presented in Equation (4) was obtained. Cuprous concentration, copper powder (g) also followed stoichiometry shown in Equations (4) - (6). Copper recovery of 75% of theoretical recovery was obtained. Total gas composition dip is at around 60 minutes of the reaction as shown in FIG. 3. Example 2. Experiments with high acid at 150°C

[0055] Experiments (i.e., CC 15 and CC 16) were performed at 150°C at pCO/pH2= 2/1 , 4 h reaction time 4 h on a solution containing 40 g/L (gram per liter) Cu and 120 g/L sulfuric acid. Results of assays are presented in FIG. 4 to FIG. 5. Only 7 g/L of cuprous was formed upon reduction under the conditions where low acid calibration experiments were performed (FIG. 4). Gas analysis curves showed a similar dip to the calibration experiment, which was tasked to re-calibrate the analyzer and check for the residual gas type and content if any (FIG. 5). Purities for all the copper precipitates were analyzed in the Atomic Absorption Spectroscopy (AAS) and compared to pure Cu analyzed under the same conditions. Purity of copper obtained was > 99.2%. Table 1 shows a purity of 99.2% obtained from CC9, CC13 and CC14, three experiments.

Table 1 : Purity of recovered copper

Example 3. Experiments with high acid at 170°C

[0056] Experiments (i.e., CC 19, CC20, CC 21 and CC 22) were performed at 170°C at pCO/pH2= 2/1 , on a solution containing 40 g/L Cu and 120 g/L sulfuric acid. Total pressure was varied 800 psig, 600 psig, 400 psig and time of reaction was also varied 4 h and 6 h. Results of assays are presented in FIG. 6a to FIG. 7b. At 170°C a maximum of copper recovery extracted from CC19 is 47% of theoretical recovery. The temperature increasing from 150°C to 170°C had a drastic effect on the kinetics of cuprous formation (FIG. 6a and FIG. 6b). Gas analyzer was recalibrated. The feed gas reads close to the syngas composition. The dip in 60 mins of total gas was ascertained to be a foreign gas in the headspace mostly N2 after the leak test of the autoclave after every experiment (FIG. 7a and FIG. 7b). It was suggested that a syngas purge be performed at the beginning of experiment to expel remnant N2 in the headspace off the autoclave. Example 4. Experiments with high acid at high temperature 180°C and 190°C

[0057] Experiments (i.e., CC23 and CC24) were performed at 180°C and 190°C at pCO/pH2= 2/1 , time 4 h, total pressure 600 psig, on a solution containing 40 g/L Cu and 120 g/L sulfuric acid. The purpose was to conduct higher temperature experiments to ascertain a high limit of temperature to carry out further optimizations. Results of assays are presented in FIG. 8 to FIG. 10.

Table 2: Cuprous Concentration in high temperature experiments

Table 3: Total copper produced against cuprous content

Table 4: Total gas composition 180°C experiments

Table 5: Total gas composition 190°C experiments

[0058] Results with high acid at high temperature 180°C and 190°C are presented in Table 2 to Table 6. 82% of theoretical copper recovery was obtained at 190°C experiment (CC23), 67% of theoretical copper recovery was obtained at 180°C (CC24). Copper powder was formed inside the autoclave at 190°C, hence the cuprous concentration at 190°C experiment was constant around 24 g/L. Gas analysis does not show a dip and accounts for 100% of gas. This concludes the presence of remnant N2 in the headspace of the autoclave in the first 60 min of the reaction.

[0059] The following are some of the key findings from Examplel to Example 4.

• Replicable results were obtained in the calibration experiments with low acid and ammonium sulfate;

• Temperature limits the kinetics of cuprous carbonyl. The optimal temperature may be > 170°C;

• N2 build up in the headspace for the first hour after the leak test at t = 0. Triple purge of feed syngas performed at t = 0 before pressure adjustment;

• 40 g/L Cu as CuSC and 120 g/L H2SO4 were attained;

• Stability of cuprous carbonyl (without disproportionating into Copper powder) depended on CO% in the headspace. Cuprous carbonyl was unstable at 50% CO/50% H2 & 66.6% CO, 33.3% H2 starting atmospheres; and

• Kinetics of reduction of cuprous carbonyl highly dependent on temperature: 180°C - 190°C.

Example 5. Experiments varying CO% in feed: 66.6% CO, 33.3% H2

[0060] In this set of experiments (i.e. , CC24, CC26, CC27 and CC30) the starting solution used was 40 g/L Cu as CuSO4, 120 g/L H2SO4; the syngas used was 66.6% CO, 33.3% H2; total pressure 600 psig and reaction time of 4h. Results are shown FIGs. 8, 11 and 12. Reduction of copper was quicker at higher temperatures. The formed cuprous carbonyl is not stable at 240 min (disproportionates in bomb sampler) at 190°C as seen on cuprous plot in FIG. 8, 80.5% conversion of theoretical recoverable of copper could be recovered at 190°C. Higher CO% in the feed gas was recommended to be used to improve the stability of the cuprous carbonyl.

Example 6. Experiments varying C0% in feed: 73% CO, 27% H2

[0061] In this set of experiments (i.e., CC25 and CC26) the starting solution used was 40 g/L Cu as CUSO4, 120 g/L H2SO4; the syngas used was 66.6% CO, 33.3% H2; total pressure 600 psig and reaction time of 4h. Temperature was varied 175°C and 185°C. Results are shown FIG. 11 and FIG. 12.

[0062] The higher CO% in syngas feed at 73% compared to 66% in Example 5 is better in stabilizing the cuprous carbonyl at high temperatures 185°C. Copper yield of 74.7% was obtained at 185°C. Next steps proposed were to investigate higher CO% in syngas and also to experiment different rich electrolyte compositions (high acid and addition of Ferrous in rich electrolyte) at 185°C.

Example 7. Experiments varying CO% in feed: higher% CO (75%, 80%) in feed syngas

[0063] In this set of experiments (i.e., CC27 and CC32) the starting solution used was 40 g/L Cu as CuSO4, 120 g/L H2SO4; the syngas used was at a total pressure 600 psig and reaction time of 4h, temperature of 185°C. CO% in syngas was varied at 75% and 80% respectively. Results are shown FIG. 13 to FIG. 15.

[0064] The increase in% CO was beneficial in stabilizing the cuprous carbonyl over the period of 4 h. Around 66.3% theoretical recovery of copper was achieved at 75% CO, 71 % of copper recovered at 80% CO (rest H2).

Example 8. Experiments with two different rich electrolyte solutions: Acid Variation [0065] In this set of experiments (i.e., CC28 and CC29), the syngas used was at a total pressure 600 psig containing 75% CO 25% H2, temperature of 185°C and reaction time of 4h. 50 g/L of copper was contained in the rich electrolyte solution. Free acid content was varied in the rich electrolyte solution 150 g/L and 180 g/L. Results are presented as FIG. 16 to FIG. 18.

Example 9. Experiments with two different rich electrolyte solutions: Acid Variation with Ferrous

[0066] In this set of experiments (i.e. , CC30 and CC31), the syngas used was at a total pressure 600 psig containing 75% CO 25% H2, temperature of 185°C and reaction time of 4h. 50 g/L of Copper was contained in the rich electrolyte solution along with 1 g/L Ferrous. Free acid content was varied in the rich electrolyte solution 150 g/L and 180 g/L. Results are presented as FIG. 19 to FIG. 21.

[0067] Two new rich electrolyte solutions containing Ferrous yielded 60% and 66% of theoretical copper recovery at 150 g/L and 180 g/L sulfuric acid respectively. Cuprous content in CC30 experiment was affected by fine copper (< 0.02 micron) passing through the filter and participating in the cuprous titrations.

[0068] Table 6 is a summary of Examples 2-8.

Table 6

[0069] In summary, the purpose of Examples 1-8 is to prove the concept of the reaction mechanism presented in Equations (4)-(6) to refine copper in rich electrolytes from solvent extraction circuits as pure copper powder precipitate. Key features are to demonstrate a 60% theoretical copper recovery (i.e., 60% x 50% = 30% total) at a 99.9% purity of copper on 2-3 synthetic rich electrolytes. The following are the key conclusions from Examples 1-8:

• A copper recovery 60% of theoretical copper recovery was achieved in 5 rich electrolyte solutions. A purity of > 99.9% of copper was achieved;

• Autoclave would be operated continuously with a small vent stream;

• Depressurization and disproportionation unit operation in the reaction mechanism may be carried outside the autoclave. After the stipulated reaction time, the contents in the autoclave may be collected in a separate vessel, copper may then be precipitated in a globe box under controlled conditions, such as in N2 atmosphere;

• The disclosed method provides a better control of disproportionation reaction and morphology of precipitated copper powder;

• CO2 analysis of off gas stream helps check if direction reduction of cupric to cuprous is taking place with CO; and

• reaction time of reduction is < 2 hrs by employing high temperature.

[0070] Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “some embodiments” or “implementation.”

[0071] As used herein, the indefinite article “a” or “an” s used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form.

[0072] As used herein, “about” or “around” or “approximately” in the text or in a claim means ±10% of the value stated.

[0073] As used herein, “high acid” refers to a sulfuric acid concentration ranging from 100 g/L to 220 g/L in a solution according to the disclosed method.

[0074] As used herein, “high ammonium” refers to an ammonium sulfate concentration ranging from 0.2 M to 1 M in a solution according to the disclosed method.

[0075] As used herein, “high copper” refers to a copper concentration ranging from 20 g/L to 80 g/L in a solution according to the disclosed method.

[0076] As used herein, “high amounts of Fe” refers to FeSC>4 concentration ranges from 1 to 10 g/L in a solution according to the disclosed method.

[0077] As used herein, “theoretical recovery” or “theoretical copper recovery” refers to a maximum recovery of copper as copper power, i.e. , 50% according to Equations (4) and (6). That is, 2 moles of copper as cupric sulfate in solution produce a maximum of 1 mole of copper as powder by reduction with CO and H2. All of the copper recoveries mentioned hereforth are based on the maximum recovery of copper as copper powder (i.e. , theoretical recovery 50%). All of the copper recoveries mentioned hereforth are based on the definition of the theoretical recovery. For example, a 65% of theoretical copper recovery means a recovery of 65% multiplying the theoretical recovery (50%), which is 65% x 50%.

[0078] The standard abbreviations of the elements from the periodic table of elements are used herein. It should be understood that elements may be referred to by these abbreviations (e.g., Cu refers to copper, etc.).

[0079] Additionally, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or”. That is, unless specified otherwise, or clear from context, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then “X employs A or B” is satisfied under any of the foregoing instances.

[0080] "Comprising" in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of “comprising.” “Comprising” is defined herein as necessarily encompassing the more limited transitional terms "consisting essentially of' and “consisting of”; “comprising” may therefore be replaced by "consisting essentially of" or “consisting of’ and remain within the expressly defined scope of “comprising”.

[0081] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

[0082] As used in this application, the word “exemplary” is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word exemplary is intended to present concepts in a concrete fashion.

[0083] Although the subject matter described herein may be described in the context of illustrative implementations to process one or more computing application features/operations for a computing application having user-interactive components the subject matter is not limited to these particular embodiments. Rather, the techniques described herein can be applied to any suitable type of user-interactive component execution management methods, systems, platforms, and/or apparatus. [0084] It will be understood that many additional changes in the details, materials, steps, and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above and/or the attached drawings.