FI117708B - Procedure for the extraction of gold in connection with the manufacture of copper - Google Patents

Description

11 - 08 METHOD FOR RECOVERY OF GOLD IN THE COPPER MAKING

FIELD OF THE INVENTION

The present invention relates to a process for the recovery of gold from the sulfur and iron-containing intermediate or waste resulting from the leaching of the copper raw material during the hydro-metallurgical production of copper. Both copper and gold are recovered in the chloride environment. The gold in the intermediate or in the waste is dissolved in divalent copper and chlorine in copper (II) chloride-sodium chloride solution under conditions of oxidation-reduction potential in the range of 650-750 mV and pH in the range of 1- 1.6. The acid produced by the chlorine supply is neutralized by the copper (II) oxychloride formed in the process. Neutralization prevents costly iron dissolution.

BACKGROUND OF THE INVENTION

U.S. Patent No. 6,007,600 describes a process for the hydrometallurgical production of copper from a copper-containing raw material, such as copper sulphide concentrate. According to the method, raw materials »·; is solubilized by countercurrent leaching with sodium chloride-copper chloride solution in several ** ·: ** '· mass steps to form a monovalent copper (I) chloride solution.

a ··: - ·: · Since the solution always contains both divalent cupric chloride and impurities of other metals, the solution is subjected to reduction and purification of divalent copper * * · 25. The pure cupric chloride solution is precipitated with sodium hydroxide into copper oxides and the oxide gas is further reduced to elemental copper. During the precipitation of copper oxide i. the resulting sodium chloride solution is further processed by chlor-alkali electrolysis, using chlorine gas and / or chloride solution as raw material. • dissolution of 30 substances, sodium hydroxide produced by electrolysis, · · · precipitation of hydrogen, and hydrogen produced for the reduction of elemental copper. The recovery of gold from the leaching residue is not specifically described in the method * *.

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Some methods have been known in the art that have been used to dissolve gold from sulfur and iron-containing materials in the copper chloride-based recovery process.

U.S. Patent 4,551,213 discloses a method according to which gold can be dissolved from sulfur-containing materials, particularly from waste from hydrometallurgical processes. The preferred starting material for the process is waste from the CLEAR process. The CLEAR process is a hydrometallurgical copper recovery process that takes place in a chloride environment and under elevated pressure. The gold-containing waste is slurried in water and the chloride content of the suspension obtained is adjusted to contain 12 to 38% by weight of chloride. The oxidation-reduction potential is adjusted to 650-750 mV and the pH is less than 0. Copper (II) chloride or iron (III) chloride is added to the suspension to oxidize the gold in the raw materials, whereupon it dissolves.

EP 646185 relates to the recovery of copper from sulfide concentrates by chloride leaching under atmospheric conditions. Dissolve from leaching waste. : gold in an electrolyte containing at least two halides, such as I · · · · 20 sodium chloride and sodium bromide. The purpose is to store copper electricity. lode the anode to oxidize the bromine complex and use it to dissolve • * ♦; ***: gold in the waste.

• · · • · ··· «

The above methods have some disadvantages. In the process of U.S. Patent 4,551,213, the dissolution conditions are very stringent. The patent states that sulfur is not soluble under patent conditions but is not * φ · universal, since the solubility properties of elemental sulfur and the iron compounds mentioned in the patent depend on the nature of the sulfur and the compounds in question.

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♦ * "; In our experiments, it has been found that when solubilizing residues formed in atmospheric conditions are treated under the conditions of the said patent, the dissolution of sulfur and iron is remarkable. They do not dissolve, nor does it mention how they are recovered from the solution. By contrast, the gold leaching method using the bromine complex in EP 646185 is not advantageous from the point of view of environmental hygiene, since harmful leaching may occur during concentrate leaching steps.

WO patent application 03/091463 describes a process for dissolving gold from iron and sulfur-containing leaching waste or an intermediate obtained by atmospheric chloride leaching of a copper sulphide concentrate. It is stated in the publication that it is possible to dissolve gold from an iron and sulfur-containing material in an aqueous solution of copper (II) chloride-sodium chloride, with bivalent copper and oxygen under conditions of oxidation-reduction potential less than 650 mV and pH 1-3. Under these conditions, the iron is not yet soluble and the sulfur is largely insoluble. This avoids the cost of removing iron and sulfur from the solution. The recovery of gold from the solution is accomplished by any of the known methods, such as electrolysis or activated carbon. This method is quite good in itself, but in practice it is somewhat slow.

: WO patent application 03/035916 describes a method in which * * *. .

. ·. : Divalent Copper Chloride Dissolved in 20 Copper Raw Materials • · · * ·. (CuCl2) is removed from the solution by doping copper with a suitable reagent. basic copper (II) chloride or copper (II) oxychloride. Copper (II) oxychloride ··· ·: · is dissolved in hydrochloric acid and the resulting copper (II) chloride solution is recycled to dissolve the copper sulfide concentrate.

• ♦ · 25

PURPOSE OF THE INVENTION

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A process has now been developed for the recovery of gold from sulfur-iron-containing intermediate or waste from copper hydrometallic ···· '.

in the case of lurgical manufacturing of copper sulphide raw material • · · • I. 30 in solution. The leaching of the raw material is carried out with concentrated aqueous alkali chloride, copper (II) chloride solution under atmospheric conditions.

* ·

The leaching results in a solution of copper having a predominantly monovalent CuCI of 4,117,708 copper chloride, but also a portion of divalent CuCl2. Bivalent copper is precipitated as basic copper (II) chloride. When oxygen or oxygen-containing gas is supplied to the leaching steps of the copper concentrate, the iron is oxidized and precipitated as an oxide or hydroxide and the precious metals dissolve except gold. The leaching of gold from the remaining precipitate is carried out with an aqueous solution of alkali chloride-copper (II) chloride and chlorine under atmospheric conditions. With the help of chlorine, the oxidation-reduction potential of the leaching step is raised to 650-750 mV. The high oxidation-reduction potential causes the precipitation of the elemental sulfur in the precipitate and results in acid formation in the step. Alkaline copper (II) chloride formed during the precipitation of at least divalent copper is preferably used to neutralize the acid. By simultaneous neutralization of the acid, the pH is maintained at 1.0 to 1.6, thereby preventing the dissolution of iron. The dissolved gold is recovered by any method known per se.

The essential features of the invention will be apparent from the appended claims.

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SUMMARY OF THE INVENTION

* ·: The gold-containing intermediate or waste is slurried in copper (II) chloride-containing sodium chloride solution for suspension and the oxidation potential for gold dissolution is achieved precisely by bivalent copper and chlorine gas. If the feed for gold leaching still contains 25 insoluble copper sulfides, an oxygen-containing gas may be introduced at the beginning of the leaching step to dissolve the copper. Chlorine gas is preferably obtained from chlorine alkali electrolysis associated with hydrometallurgical recovery of copper concentrate. The oxidation-reduction potential is measured with Pt and Ag / AgCl electrodes and kept at 650-750 mV. Bivalent ···. The amount of 30 copper, Cu 2+, in the solution is preferably 20 to 80 g / l and sodium chloride * ·· is in the range of 200 to 330 g / l. Gold dissolves as a chloro complex according to the reaction • ·: 5 117708

Au + 3 Cu2 + + 6 Cl "-> AuCl4 '+ 3 Cu ++ 2 Cl' (1)

The dissolution takes place under atmospheric conditions at a temperature ranging from room temperature to the boiling point of the suspension, preferably at 80 ° C to the boiling point of the suspension.

Thus, it has now been found in experiments that the so-called reactive sludge with chlorine gas increasing the redox potential will accelerate the dissolution of gold. However, acceleration has its downsides. Increasing the redox potential increases the dissolution of the element (S °) in the solute, which is likely to occur according to the following reaction (2).

S0 + 3 Cl2 + 4 H2O H2SO4 + 6 HCl (2) The reaction (2) shows that a large amount of acid is formed (8 mol H + / mol SQ). However, the acid generated in the solution must be neutralized because below pH 1 the iron in the solids begins to dissolve. The dissolution of iron causes costs in the process as the dissolved iron circulates and precipitates Cu2 + -. precipitation and consumes reagents. A preferred pH range for retaining iron in the precipitate is still 1.0 to 1.6.

• ·· • · • · · · · · **. ···. According to our invention, · · · the bases produced by the precipitation of divalent copper are used to at least neutralize the hydrochloric acid formed ····: ** ·. copper (II) chloride with the mineral name acacamite and the chemical formula ··· 25 Cu2 (OH) 3Cl. This procedure generates significant cost savings: compared to the conventional procedure. The basic copper (II) chloride is soluble and: ["m: the resulting copper (II) chloride can be used to leach the raw material. If. ·. Copper (II) oxychloride is not passed to this step, however, its solubilization requires * · *. * ** .the acid which must then be otherwise produced Neutralization of the hydrochloric acid and dissolution of the · · · · m. 30 copper (II) oxychloride is carried out according to the following reaction: • 3 · Cu (OH) 2 -CuCl 2 + 6 HCl-> 4 CuCl 2 + 6 H 2 O (3) 6 117708

The sulfuric acid produced can be neutralized, for example, with lime: H2SO4 + CaCO3 -> CaSO4 2H2O + CO2 (4) 5

Of course, another base such as sodium or potassium hydroxide may be used instead of lime. The gold is recovered from the solution in some manner known per se, such as activated carbon, electrolysis, or chemical precipitation.

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LIST OF FIGURES

The process of the invention is further illustrated in the flow chart of Fig. 1, where gold recovery is combined with copper hydrometallurgical recovery.

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DETAILED DESCRIPTION OF THE INVENTION

According to Figure 1, copper sulfide feedstock such as copper sulfide concentrate 2 is fed to the first leaching step 1 and recycled to the step, ·. j also the solution 3 from the later process step, which is · · ·, ·. · 20 Copper (II) aqueous solution of chloride-sodium chloride. Thicker arrows represent • * · • ·. ·, Solids and thinner arrows flow through the solution. The phase always contains one k · k. * ··. or more reactors and thickening. Copper concentrate copper dissolves • months ··· mainly in process solution and solution 4 contains copper chloride with • · * * · '**: approximately 70 g / l copper, mainly monovalent. The divalent copper · · * 25 solution is alloyed in a precipitation step 5 with a suitable alkali or alkaline earth such as t4 µ, for example, caustic NaOH or CaCO3 lime. The solution in which all the copper is now monovalent is led to solution purification 6 and then to the copper oxide precipitation step 7. The ···· sodium chloride solution from the copper oxide precipitation is passed to chlor-alkali electrolysis 8 where k k k 30 of chlorine and hydrogen gas are used. as reagents in the process. Hydrogen can be used, for example, in the * 9 reduction of copper oxide 9 and, if necessary, in the preparation of 117708 7 hydrochloric acid together with chlorine according to the following reaction: H2 + Cl2 = 2 HCl (5) 5

Dissolution of the solid 10 from the first leaching step is continued in the second leaching step 11 with the solution 12 obtained from the subsequent process step. In order to enhance the leaching of this step, air is supplied to the reactors. At the end of the step is thickening.

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Solution 3 from the second leaching step is led to the first leaching step 1 to dissolve the concentrate. The leaching of the solid 13 from the second leaching step is continued in the third step 14 to leach the remaining copper and gold. In the third leaching step, i.e. the leaching of gold 15, the precipitate is leached with copper (II) chloride-sodium chloride solution 15 having a Cu 2+ content of 20 to 80 g / l and a sodium chloride concentration of 200 to 330 g / l. If the precipitate entering this leaching step still contains undissolved copper sulfide, it may be introduced into the first reactor at the beginning of the step. : also oxygen most preferably in the form of air. Copper sulphide must be dissolved out of the precipitate before the gold dissolves. To increase Redox potential * ·; in the range of 650-750 mV, the reactor is also fed with chlorine gas 16 from process-related chlor-alkali electrolysis 8. Because of its high potential, the sulfur begins to dissolve and, as a result, the acid is formed in step. In order to ensure that the pH of the step does not fall below 1.0, 25 bases formed from the precipitation of divalent copper are fed there. * J * copper (II) chloride 17. In addition, * * · other bases can be added if necessary.

The gold chloride complex solution from the leaching step 18 is either: ···. 30 as such or filtered for gold recovery, which in this exemplary case occurs on a carbon column 19 with activated carbon. The columns yield a gold product 20. The solution leaving column 19 is a gold-free solution 21,817,708 which is recycled to the second stage 11 of leaching and, if necessary, a sodium chloride solution is introduced therein to obtain a suitable concentration of copper (II) chloride. The gold recovery step precipitate, after normal post-treatment such as filtration and washing (not more specifically in the figure), is the final leaching residue 22 which contains almost all the sulfur and iron in the concentrate. The precipitate filtrate and washings are returned to the concentrate leaching process, for example.

The flow chart of Figure 1 illustrates the gold leaching process in connection with the leaching of the copper-bearing raw material, but the method of the invention is not specifically bound to the leaching process of the copper-bearing raw material. It is central to our process that the leaching of the gold-containing material is carried out with divalent copper and chlorine under conditions which increase the solution's redox potential to 650-750 mV and neutralize the acid formed during sulfur dissolution to a pH of at least 1, preferably at least 1. , 0 to 1.6.

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. ·. : EXAMPLES

• t · * ·. ·. The invention will be further described by the following examples, of which example 1 is • · · 4 • *. prior art and Example 2 illustrates a process according to the invention.

• * · * * · · · · · *

Example 1 • · · 25 Gold was leached from the leaching residue of chalcopyrite concentrate in a one-liter reactor equipped with a stirrer. The waste was generated *** '' '

by dissolving conventional chalcopyrite copper concentrate in U.S. Pat

* ··· In a laboratory-scale three-stage countercurrent leaching of 6,007,600, the waste contained 3.7% Cu, 28.9% Fe, 32.4% S and 5.8 ppm Au.

* · ·. ···. A synthetic solution containing about 40 g of Cu2 + as chloride and • · v was used for dissolution. 300 g NaCl / L. The test temperature was 40 ° C and the redox potential was maintained at 690-700 mV (AgCl / Ag vs. Pt) with chlorine gas. The experiment lasted 12 hours and the yield of 9 117708 gold was about 83%. During the test, the pH and solution analyzes of the solution changed as follows:

Time (h) pH Fe (g / L) S (g / L) Au (mg / L) Ö TT96 ÖÖ m 0.00 ”2 0.60 5 ^ 8 1 ^ 42 Ö58 4 Ö47 Ϊ05 2 ^ 26 Oil 8 0, 08 3Λ0 8 ^ 54 M6 12 07Ϊ3 42 ^ 6 9 ^ 33 1 ^ 28 5 The results show a strong acid formation which resulted in abundant iron dissolution.

Example 2

A laboratory-scale continuous three-phase countercurrent leaching, including the Cu2 + removal step, according to US Patent No. 6,007,600 was run. In the removal step, divalent copper was precipitated from the product solution as basic copper (II) chloride, and additionally precipitated: µ Fe completely and SO42 quite fairly.

The leaching reactors were 5 L. The third stage of leaching, where gold was leached, consisted of two reactors R4 and R5. Their operating temperature was 90 ° C and their redox potential (AgCl / Ag vs. Pt) was adjusted with chlorine gas and the pH was adjusted by precipitation of Cu 2+ precipitation. A synthetic solution containing 40 g of Cu2 + chloride and 280 g of NaCl / L was used as solvent. The solution delay of step 20 was of the order of 10 h. The input of the step was the precipitate of the preceding reactor R3 · · 1. The solids analyzes for one week were as follows: • · · ** 1 ...

• · · · • · • * * · · · 25 • * · · 10 117708

Solid Cu (%) Fe (%) S (%) Au (ppm)

Concentrate 28fi 3Ö / 7 34 ^ 0 5 ^ 5 _____ - _ - - _R4-pk 2? I 30 ^ 5 3Ö4 T _ i _R5-pk ÖJ 28 ^ 2 3Ϊ7 0.7

Cuz + precipitate 32 ^ 2 iJj 3.1 "It is seen that good dissolution yields of Cu and Au were obtained, which were in the order of 98 and 87%, respectively. The solution analyzes and the pH and redox values were as follows: 5

Soluble Cu (g / L) Fe (g / L) S (g /) pH Redox (mV)

Feed 4 4 0.0 0.0 2 ^ 0 R4 solution 55 5.0 VS T |5 66Ö R5 solution 55 M 1 ^ 3 M 7ÖÖ It is seen that, despite the high redox potentials, the Fe of the solution leaving the previous leaching step and S concentrations were · ·; quite reasonable. Thus, a precipitate containing alkaline copper (II) chloride performed its · · 10 function and dissolved quite well.

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Claims (15)

A process for recovering gold from an iron or sulfur-containing intermediate or leaching residue from atmospheric chloride leaching of a copper sulphide feedstock, wherein the gold is leached from the intermediate or waste in an aqueous solution of copper (II) chloride and the oxidation-reduction potential of the formed suspension is maintained at 650-750 µM, characterized in that the acid formed during the sulfur dissolution is neutralized with at least copper (II) oxychloride and thus the pH is maintained at 1-1.6, leaving the iron essentially insoluble; the dissolved gold is recovered in some manner known per se. Process according to Claim 1, characterized in that the amount of divalent copper in the solution is 20 to 80 g / l. Method according to claim 1 or 2, characterized in that. the amount of sodium chloride in the solution is 200 to 330 g / l. * · 1; 20 • · · • · ·. . ·! Method according to one of Claims 1 to 3, characterized in that * · · * 1 ·. · 1 ·. keeping the temperature within the range of 80 ° C - the boiling point of the suspension. • · · «M 5. Förfarande enligt verge av patentkraven 1-4, kännetecknat av att vid • · • · *** den atmospheric chlorideslakningen av det sulphidiska rämaterialet för 14 1 1 7708 bucket and bagpipe bag loser sig i stort sett som envärd och den bildade tvävärda kopparn falls ut ur lösningen med alkali eller jordalkalii form av koppar (ll) oxychloride som leds till neutralization av syran som pictures vid lakningen av guld. 5 The process according to any one of claims 1 to 4, characterized in that in the atmospheric chloride solvent solvent of the copper sulphide raw material, the copper in the raw material is essentially soluble and the resulting divalent copper is precipitated from the solution by alkali or alkaline earth. . ·. with copper (II) as oxychloride, which is conducted in gold leaching ··· .1 ··. to neutralize the resulting acid. • · ♦ 30 • · · • · · · «1 · • · · 1 12 1 1 7708 6. Förfarande enligt face av patent kraven 1-4, kangnetecknat av att vid neutralizingen av den syra som bildas vid lösningen av svavel anchovy lime, sodium elleric potassium hydroxides. 7. Förfarande enligt face av patent kraven 1-6, kännetecknat av att chloro erhälls frän chlor-alkali electrolysis i samband med förfarandet för lakning av detulfidiska lämteret for bucket. Process according to one of Claims 1 to 4, characterized in that lime, sodium or potassium hydroxide are used to neutralize the acid formed during the dissolution of the sulfur. Process according to one of Claims 1 to 6, characterized in that the chlorine is obtained from the chlor-alkali electrolysis associated with the process for dissolving the copper sulphidic raw material. 8. Förfarande enligt patentkrav 7, kännetecknat av att den 15 copepod (l) chloride-alkali chloride solution in water atmosphere atmospheric chloride acid in sulphidic waste material, copper oxide-copolymerizer, varifran e en alkali chloride chloride solution, och vätgas samt. alkali hydroxide pictures for att användas i processens olika steg. * * * '20 • · · • · The process according to claim 7, characterized in that the copper (I) chloride-alkali chloride solution formed by atmospheric chloride leaching of the sulfide raw material of copper is passed to a copper oxide purchase which is further passed to a chlor-alkali electrolysis to produce chlorine and hydrogen at different stages of the process. 9. Förfarande enligt nägot av patentkraven 1-8, kännetecknat av att • · ·. · * · '. lakningen av copar sulfide ur mellanprodukten eller äterstoden utförs • · lit .:. med hjälp av en vattenlösning av koppar (ll) chloride-sodium chloride och en • · · ·. ···. syrehaltig gas fore lakningen av guld. * * * 25 •: *: 10. Förfarande enligt patentkrav 9, kännetecknat av att den syrehaltiga • * · gasen är luft. • · * • · * * · • · ...!: 11. Förfarande enligt patentkrav 9, kännetecknat av att den syrehaltiga. *. 30 gasen är sirreanrikad luft. • · · • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 117 117 Process according to one of Claims 1 to 8, characterized in that the dissolution of the copper sulphide from the intermediate or the waste is carried out with the aid of an aqueous solution of copper (II) chloride and sodium chloride before dissolving the gold. • · ·. ·. : 20 ♦ · · • ·. . *. A process according to claim 9, characterized in that the oxygen-containing gas is air. • · 9 • · · · · · · The process according to claim 9, characterized in that the oxygen-containing gas is oxygen-enriched air. The process according to claim 9, characterized in that the oxygen-containing gas is oxygen. * * · • * »• · • · ··· 12. Förfarande enligt patentkrav 9, kännetecknat av att den syrehaltiga gasen är syre. 13. Förfarande enligt face av patentkraven 1-12, calligraphy av att 5 det cavity bed utvinns med hjälp av active moth. A method according to any one of claims 1 to 12, characterized by:. of recovering dissolved gold with activated carbon. • · • · · 1 1 7708 Process according to one of Claims 1 to 12, characterized in that the dissolved gold is recovered by electrolysis. Process according to one of Claims 1 to 12, characterized in that the dissolved gold is recovered by chemical precipitation. io 1. Förfarande för utvinning av guld ur en mellanproduct eller en lösningsäterstod innehällande järn och svavel som bildas vid atmospheric chlorides lakning av sulfidiskt ramaterial för koper, colors gül lacs ur mellanproducten eller Atterstoden i en vattenlösl med is hjälp av tvärärd bucket i lösningen och chlorine, color den bildade suspensionens oxidationreduktionspotential variations 650-750 mV, kangnetecknat av att syran som bildas vid lakningen av svavel neutraliser med ätminstone bucket (ll) oxychlorides och. vid dumplings 1-1.6, colors of the stern i stort sett förblir olö; det urlakade I M \ 20 guldet utvinns pä Face i och för sig stump setting. • · * * · • · · • · ·,, ···. 2. Förfarande enligt patentkrav 1, kännetecknat av att toyden tvävärd • * koppar i lösningen är 20 - 80 g / l. 3. Förfarande enligt patentkrav 1 eller 2, kännetecknat av att toyden: sodium chloride 200 g to 330 g / l. * · · * · * · • * • · ·. ···. 4. Förfarande enligt nagot av patentkraven 1-3, kännetecknat av att • temperature temperature inom omrädet 80 ° C - suspensionens cocktail. • · 30 • · · 14. Förfarande enligt face av patent kraven 1-12, kanknetecknat av att det cavity bed utvinns genome electrolysis. io 15. Förfarande enligt face av patentkraven 1-12, kännetecknat av att det urlakade guldet utvinns genom chemisk utfällning. • • ♦ • · · # # * «« «« «« «« »» »» »» » * • * • «· • • • * 9 * · # * * * * • • · · · · · · · · · · · · · · · · · · · · · · · · · · • · · • • e · 1 ···. ·· ♦ • · ♦ ·