Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/02—Preparation of sulfur; Purification
  • C01B17/06—Preparation of sulfur; Purification from non-gaseous sulfides or materials containing such sulfides, e.g. ores

Definitions

• An electrolyte comprising a soluble metal chloride selected from the group consisting of soluble chlorides of aluminum, chromium, copper, iron, manganese, nickel, zinc and rare earth metals alone or mixed or in combina tion with alkali metal and/or alkaline earth metal chlorides, the electrolyte being at least .5 normal in chloride
• U.S. Pat. No. 2,839,461 discloses an electrolytic process for the recovery of nickel from nickel sulfide but it is dependent upon the formation of a highly conductive nickel sulfide matte anode and is not applicable to low grade concentrates.
• Such common sulfide minerals as galena, sphalerite, chalcopyrite, and chalcocite have resistivities many times that of the anode used in the processes of Pat. No. 2,839,461 and, therefore, that process cannot be used with these minerals.
• metal sulfide as used herein is inclusive of the complex as well as the simple sulfide minerals which contain economically recoverable quantities of the specified metals.
• the invention is a pollution-free process for the recovery of the metals of Groups IB, IIB, IVA, V-A, VI-A and VIII of the Periodic Table, from their sulfide and mixed sulfide ores or concentrates in which the sulfide is electrolytically dissociated in an acid aqueous media into elemental sulfur and metal ions which are then recovered from solution in the electrolyte media by conventional pollution-free techniques.
• the electrolysis process is characterized by certain critical process conditions which render it economically feasible, these being the use of:
• An electrolyte comprising: a soluble metal chloride selected from the group consisting of soluble chlorides of aluminum, chromium, copper, iron, manganese, nickel, zinc and rare earth metal chlorides either alone or mixed in combination with alkali metal and/or alkaline earth metal chlorides, said electrolyte being at least .5 normal in chloride ion,
• soluble halide salts including the bromides, iodides and fluorides, of aluminum, chromium, copper, iron, manganese, nickel, zinc, and rare earth metals, are operative for the purpose of the invention; however, they are not as economically attractive as the chlorides of these metals.
• Soluble halide metal salts in general are operative as electrolytes for recovering metals from their sulfides in accordance with the process of the invention.
• the process parameters which have been found to control the current requirements for the process are electrolyte composition, feed particle size, operating pH range, operation temperature, and anode current density. As the examples which follow show, these factors are mutually interacting and dependent as respects their effect on cur rent requirements.
• sulfide ores and concentrates of metals of Groups I-B, II-B, IV-A, V-A, VIA and VIII of the Periodic Table are characterized by certain similar properties related to the electrolytic dissociation to elemental sulfur and metal ions therefrom by the process of this invention. For example, their sulfides all have relatively low conductivities. While certain nickel sulfides are relatively good conductors, others are not.
• the metal ions of these sulfides are most favorably produced by electrolysis in aqueous acidic electrolytes of soluble chlorides of aluminum, chromium, copper, iron, manganese, nickel, zinc, rare earth metals, alkali metals, and alkaline earth metals, and mixtures thereof, at a pH range of up to about 3.9 using anode current densities above about 12 amperes/ft. with a sulfide feed particle size smaller than about 60 mesh US. Standard, and a temperature range between about 60 C.-l05 C. for the alkali and alkaline earth metal chlorides and between about 50 C.-l05 C. for the other electrolytes.
• the examples which follow illustrate that the power requirements for the process applied to recover the stated metals from their sulfides are well within the limits of commercial feasibility.
• the minerals containing the metals which can be recovered by the process often contain the metals in the form of complex or mixed sulfides.
• the electrolytic media for the process must be acidic as an alkaline electrolyte has proven unsatisfactory for recovery from their sulfides of the defined metals to which the invention is related. Elemental sulfur is not stable in an alkaline media because oxidation of the sulfur proceeds rapidly through thiosulfate, hydrosulfite, sulfide to sulfate. The presence of sulfate ions is undesirable because at high sulfate concentrations oxygen is rapidly evolved at the anode resulting in a decrease in current 4 efiiciency. Further, it was found that at high current densities in the presence of sulfate graphite anodes Were appreciably attacked and this type anode is the most satisfactory.
• Ferrous chloride is particularly effective as an electrolyte for dissociation of chalcopyrite as this compound is produced in quantity by the electrolytic dissociation of chalcopyrite in an acid medium.
• Aluminum chloride is particularly suited as an electrolyte for the dissociation of lead sulfide ores and concentrates, leadzinc and lead-silver concentrates, because of the high solubilities of lead and silver chloride in aluminum chloride. This discovery is highly unexpected in view of the insolubility of lead and silver chlorides in most solvents.
• Zinc chloride is preferred with zinc ores essentially free of lead.
• Concentrations of chloride ion in excess of .5 normal to saturation may be used for the process. Voltage across the cell is lower at higher salt concentrations and the latter are preferred except Where low grade feeds are used and where salt losses would therefore become significant.
• the particle size of the feed material is critical as it directly affects the conversion of sulfide sulfur to elemental sulfur.
• the elemental sulfur produced is extremely fine.
• the anode current attacks the metal sulfide preferentially to sulfur provided the sulfide has sutficient activity near the anode.
• the activity of the sulfide is a function of its concentration and its exposed surface area. Therefore, the presence of a high concentration of fine sulfide near the anode prevents the continuing oxidation of sulfur and results in higher efficiency and conseqeuntly lower current consumption.
• An average grain size for the feed sulfide smaller than about 60 mesh U.S. Standard is the operable range and is compatible with other critical parameters.
• a pH range for the electrolytic media up to about 3.9 is preferred. Current efiiciency is reduced at pHs above 3.9 and at very high acidities (low pH values) in the absence of substantial concentrations of the specified metal chlorides. In certain cases such as that of aluminum chloride which hydrolyzes at about pH 2.0, chromic chloride which hydrolyzes at about pH 3.0, and rare earth metal chlorides which hydrolyze at about pH 4.0, the acidity must be strong enough to prevent this hydiolysis.
• the preferred pH range is 0.3-0.8.
• the pH of the electrolyte is conveniently adjusted with hydrochloric acid.
• the reaction temperature of the electrolyte is critical and high process efficiency is not obtainable at low temperature.
• the preferential attack on the sulfide over elemental sulfur is accentuated at high temperatures and, indeed, at temperatures below 50 C. a substantial portion of the sulfide is converted to undesirable sulfate.
• the operable range is about 50 C.l05 C. when used in conjunction with the other critical factors. A temperature of C. is most preferred.
• the anode current density is also critical as used with the other critical parameters with a preferred range being above about 12 amperes/ft. anode current density.
• anode current density In contrast to the earlier prior art teaching (U.S. Pat. No. 2,761,829) it was found that high copper dissociation in copper sulfide concentrate in the presence of iron sulfide (pyrite) was attained at current densities of 240 .amperes/ft.
• a preferred current density range is 120-240 amperes/ft. Where pyrite predominates current densities of between 60-120 'amperes/ft? are preferred.
• current anode density may 6 in the process of the invention as operated within the critical parameter ranges of temperature, current density, pH and particle size.
• anode current density between 40-120 amperes/ft. may be used.
• anode current density between 40-120 amperes/ft.
• the necessities of cell geometry will dictate the anode current density.
• current densities 100-200 amperes/ft. are preferred at the cathode and this range of current density is suitable for high grade copper concentrates.
• plating lead or zinc at the cathode a current density range of 20-30 amperes/ft. is preferred at the cathode and is suitable for the anode.
• the following examples with results are illustrative of the process of the invention but not limiting thereof.
• the process is not limited to a specific electrolytic cell design or type of cell.
• the cells used in the examples comprised an anode section containing a suitable anode such as graphite or coated titanium, provided with means for agitation and heating, and separated from the cathode section by a diaphragm.
• the cathode section consisted of a suitable cathode of stainless steel, copper, lead or aluminum depending upon the metal being plated or the cathode reaction desired and was provided with means for liquid circulation and heating.
• ACD is given in amperes/ft. current requirement is 55
• the percent sulfur converted to elemental sulfur is computed by dividing the amount converted to elemental sulfur by the total amount of sulfur converted from sulfide sulfur and is expressed in percent.
• the metal dissolved in the electrolyte can be finally recovered by conventional methods such as, electrolysis, precipitation, cementation, etc., depending on the metal being recovered. In certain cases the metal can be plated out on the cathode during the dissociation process and recovered in this manner.
• Elemental sulfur is readily recovered from the electrolyte media by the process disclosed in co-pending application Ser. No. 233,352, filed in the U.S. Patent Office on Mar. 9, 1972, William G. Kazel, entitled Sulfur Recovery Process.
• EXAMPLE 1 The following tests were selected to illustrate the operativeness of aluminum chloride and ferrous chloride alone and with an alkali metal chloride as electrolytes of sulfide sulfur to elemental sulfur with low current consumption demonstrates the effectiveness of the electrolytes under the conditions for a representative metal sulfide.
• cupric chloride and chromic chloride the copper was recovered essentially as cuprous copper resulting in very high electrical efliciency.
• the copper recovered using cupric chloride and chromic chloride electrolytes was essentially cupric copper, this accounting for the somewhat higher current consumptions.
• the higher valent forms of copper and chromium are preferred because the lower valent forms have limited solubility.
• cuprous chloride may be used as the electrolyte instead of cupric chloride.
• the example illustrates that lead, zinc, and silver can For each test 400 grams of a 60 mesh particle size be recovered from their sulfides by the process of the low grade sulfide ore concentrate assaying by weight invention using a representative chloride electrolyte for 8.33% nickel, 0.337% colbalt, 5.16% copper and 37.8% the process of this invention and that the process is pariron were slurried in 2 liters of electrolyte and subjected ticularly effective for these metals with an aluminum to 60 amp'ere hours of current under the conditions shown. chloride electrolyte.
• ACD (amps/ft!) 12o 12o- 12 Amp-hrs/lb. Cu re- 1,566 463 558.
• EXAMPLE 10 The following tests were performed to demonstrate the effectiveness of zinc chloride as an electrolyte.
• the process is effective for the electrolyte recovery of the metals arsenic, cadmium, antimony and selenium from their sulfide ores.
• the process is equally effective for the recovery of bismuth and tellurium from their sulfides.
• the invention provides a process for recovery of the metals from their sulfide and mixed sulfide ores which has the advantages of being commercially feasible and pollution free.
• a process for the recovery of metals of Groups I-B, IIB, IV-A, V-A, VI-A and VIII of the Periodic Table from their sulfides and mixed sulfides, and mixtures thereof, by electrolysis with the formation of elemental sulfur and metal ions which process comprises:
• Test No 1 2 3 4 Electrolyte 3 M ZnCl 1.5 M ZnClr 3 M ZnCh 3 M ZnOlz.
• ACD amps/IL
• test No. 4 was performed at a 3.5 pH which than about 60 mesh US. Standard; is near the top of the critical pH range of 3.9 and this (0) maintaining the temperature of the electrolyte test shows the adverse efiect of low acidity on conversion media at about 50 C. to C., and the pH of of sulfide sulfur to elemental sulfur.
• the electrolyte media below about 3.9 while intro- 1 1 ducing electric curernt into the electrolytic cell to provide an anode current density above about 12 amperes per square foot to dissociate the metal sulfide into metal ions and elemental sulfur;
• metals are selected from the group consisting of antimony, arsenic, cadmium, copper, cobalt, iron, lead, nickel, selenium, silver and zinc.
• a process for the recovery of metals of Groups I-B, II-B, IV-A, V-A, VI-A and VHI of the Periodic Table from their sulfides and mixed sulfides, and mixtures thereof, by electrolysis with the formation of elemental sulfur and metal ions which process comprises:
• an electrolyte in an electrolytic cell including at least an anode and a cathode, the elect-rolyte comprising an acidic aqueous solution of at least one soluble halide salt selected from the group consisting of soluble halide salts of aluminum, chromium, copper, iron, manganese, nickel, zinc, and rare earth metals, and mixtures thereof, the solution having a concentration from about .5 N to saturation;

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Cited By (17)

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• 1972
  • 1972-04-21 US US00246435A patent/US3736238A/en not_active Expired - Lifetime
  • 1972-07-21 CA CA147,684A patent/CA1006843A/en not_active Expired
  • 1972-12-29 IT IT9833/72A patent/IT970635B/it active
• 1973
  • 1973-02-02 GB GB522573A patent/GB1362943A/en not_active Expired
  • 1973-02-15 ZM ZM19/73A patent/ZM1973A1/xx unknown
  • 1973-02-16 PH PH14353*UA patent/PH9597A/en unknown
  • 1973-02-22 FR FR7306816A patent/FR2180661A1/fr not_active Withdrawn
  • 1973-03-27 DE DE2315284A patent/DE2315284A1/de active Pending
  • 1973-04-18 AU AU54656/73A patent/AU466261B2/en not_active Expired
  • 1973-04-18 ES ES413885A patent/ES413885A1/es not_active Expired
  • 1973-04-19 LU LU67459A patent/LU67459A1/xx unknown
  • 1973-04-19 IE IE631/73A patent/IE37552B1/xx unknown
  • 1973-04-19 ZA ZA732705A patent/ZA732705B/xx unknown
  • 1973-04-20 BE BE130239A patent/BE798509A/xx unknown
  • 1973-04-20 NL NL7305656A patent/NL7305656A/xx unknown
  • 1973-04-20 JP JP48044992A patent/JPS4921301A/ja active Pending

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