JP2011513583A - Selective gold extraction method from copper anode slime with alcohol - Google Patents

Abstract

The present invention relates to a method for recovering gold from an acid digest of gold-containing copper anode slime. The acid lysate is selectively extracted with an alcohol having low miscibility with water. Gold is then recovered from the resulting alcoholic extract.

Description

  The present invention relates to the recovery of gold from copper anode slime.

BACKGROUND OF THE INVENTION Anode slime derived from electrolytic refining of anodic copper contains significant amounts of gold and silver. The treatment of the slime is complicated due to the presence of impurities such as Te, Se, Pb, As, and Bi. The methods employed in commercial operations to recover gold and silver from such feedstocks depend largely on the individual feedstock composition, but generally to remove copper and possibly tellurium. With leaching. Usually roasting and / or smelting is used to control lead and selenium. Next, silver is recovered by electrolysis, and finally gold is recovered by electrolytic refining.

  Oxidative chlorination of the decoppered anode slime provides an opportunity to separate silver and gold early in the process, thereby reducing gold lock-up time, and thus easier and more complete Is an attractive processing option in that it provides a hydrorefining flow sheet. The oxidative chloride leaching eliminates most of the silver to a residue to form a solution from which gold can be recovered by solvent extraction. This approach is based on the Kennecott chloride process (Hoffmann, JE, Sutliff, KE, Wells, BA and George, BD, Proceedings of COPPER 95 International Conference, Ed. WC Cooper, JE Dutrizac, H. Hein, G. Ugarte, The Metallurgical Society of CIM, vol III, pp 42 (Non-patent Document 1)) and MinataurTM process (Feather, A., Sole, KC and Bryson, LJ, The Journal of the South African Institute of Mining and Metallurgy, July / August 1997, pp 169 (Non-Patent Document 2); Feather, A., Sole, KC and Bryson, LJ, Randol Gold Forum '97, Monterey, California, USA, 1997 (Non-Patent Document 3)) Used in In the Kennecott process, chlorination is applied to the decoppered slime, and gold is extracted from the solution by dibutyl carbitol, which is a solvent with several significant disadvantages, one of which is Its solubility is high in the aqueous phase. The Minataur ™ process has been applied to gold mud but has not been tested in solutions containing higher concentrations of impurities resulting from direct treatment of decopperized slime. A typical hydrorefining approach uses oxidative chloride leaching of decopperized slime, which separates silver and gold in the early stages of processing and recovers gold from the leachate by solvent extraction. It becomes possible. A simplified flow sheet is shown in FIG. This type of hydrometallurgical approach to the treatment of anodic slime is practiced at various refineries around the world. These types of processes are claimed to have significant advantages over conventional processes.

As mentioned above, DBC has been used to extract gold from liquids derived from hydrochloric acid digestion of copper anode slime. DBC has a high selectivity for gold, but has the following drawbacks:
-Phase separation in DBC extraction is very slow and requires a very long sedimentation rate.
DBC has a high solubility in the aqueous phase (0.3% or 3000 mg / L). It is necessary to recover DBC from the residual liquid by steam distillation.
• It is recommended to filter the residue from the solvent extraction DBC circuit.
-Because the phase separation time is very long, the scrubbing of organic matter in the DBC circuit is carried out by the batch method. And
Gold can only be stripped from the solvent by reduction. In the reduction, solids are introduced into the back-extraction circuit, resulting in a residue, and three phase separation steps are required. Moreover, the recommended operating temperature for the reduction is 75-80 ° C.

  Thus, there are several incentives to develop more practical solvent extraction methods for extracting gold from liquids such as, for example, chloride solutions derived from leaching of decoppered anode slime.

Hoffmann, JE, Sutliff, KE, Wells, BA and George, BD, Proceedings of COPPER 95 International Conference, Ed.WC Cooper, JE Dutrizac, H. Hein, G. Ugarte, The Metallurgical Society of CIM, vol III, pp 42 Feather, A., Sole, K.C. and Bryson, L.J., The Journal of the South African Institute of Mining and Metallurgy, July / August 1997, pp 169 By Feather, A., Sole, K.C. and Bryson, L. J., Randol Gold Forum'97, Monterey, California, USA, 1997

The object of the present invention is to substantially overcome or at least ameliorate one or more of the above-mentioned drawbacks.

SUMMARY OF THE INVENTION In a first aspect of the invention, there is provided a method for recovering gold from an acid digest of a gold-containing copper anode slime, the method comprising:
(a) selectively extracting the acid lysate with an alcohol having low solubility in water to form an alcohol extract containing gold; and
(b) recovering gold from the alcohol extract, and the gold in the acid solution is in a form that can be extracted into the alcohol.

  The acid lysate can be an aqueous acid lysate. Gold in the acid lysate can be present as a denomination dissolved in the acid lysate. This denomination may be extractable in alcohol. The denomination may be capable of reacting with an alcohol to form a second denomination that can be extracted into the alcohol.

  The following options can be used in conjunction with the first aspect, either individually or in any appropriate combination.

  The alcohol may have a solubility of less than about 0.2 w / w%, v / v%, or w / v% in water at 20 ° C. The alcohol can be a primary alcohol. The alcohol can be a branched chain alcohol. The alcohol can be, for example, 2-ethyl-1-hexanol, 8-methyl-1-nonanol, or a mixture thereof. The alcohol may be capable of selectively extracting gold from the anodic slime acid lysate.

  The method may also include the step of dissolving the gold-containing copper anode slime using an acid to provide an acid lysate. The dissolving step may include combining anodic slime with a concentrated mineral acid, such as concentrated hydrochloric acid. The acid may be combined with anodic slime in a ratio sufficient to achieve an acid concentration of about 3N to about 5N (eg, about 4N) in the acid lysate. The method can include dissolving the gold-containing copper anode slime using an acid and an oxidizing agent to provide an acid lysate. The dissolving step may include combining anodic slime with a concentrated mineral acid such as concentrated hydrochloric acid and an oxidizing agent such as hydrogen peroxide. The acid may be combined with anodic slime in a ratio sufficient to achieve an acid concentration of about 3N to about 5N (eg, about 4N) in the acid lysate. An oxidizing agent is added to the anode slime in an amount sufficient to ensure that the gold in the slime is dissolved under the conditions used, or to ensure that at least about 90% of the gold in the anode slime is dissolved. obtain.

  The gold-containing copper anode slime can be a decoppered anode slime. Thus, the acid lysate can be a copper anodic slime acid lysate.

  The acid lysate can include a radioactive element (eg, a radioactive metal) and the radioactive element cannot be extracted into the alcohol. The radioactive element can be, for example, polonium. The radioactive element can be polonium-210 or lead-210 or bismuth-210. There may be more than one radioactive element. In some cases, no radioactive elements are extracted into the alcohol. The acidity of the acid lysate can be the acidity such that gold is extracted into the alcohol and no radioactive elements are extracted into the alcohol. Less than about 10% of the amount of radioactive elements present in the acid lysate can be extracted into the alcohol. The acidity of the acid lysate is such that at least about 90% of the gold present in the lysate is extracted into the alcohol, and less than about 10% of the amount of radioactive elements present in the acid lysate is in the alcohol. It can be as acidic as it can be extracted.

  The ratio of gold to total metals (or cations) in the acid solution prior to step (a) can be less than about 4% by weight or molar ratio. This proportion can be taken to refer to the proportion of metal atoms (or cations) in the acid lysate.

  Step (a) of the method may include continuous countercurrent extraction.

  The method can further include scrubbing the alcohol extract. The scrubbing can be aimed at removing impurities from the aforementioned extract. This step can be performed between steps (a) and (b). The scrubbing may include scrubbing with a dilute mineral acid. In this context, an impurity may mean one or more species including a non-gold metal, metalloid, or metalloid.

  Step (b) can include extracting the alcohol extract with an aqueous extraction solvent to provide a gold-containing aqueous extract. The aqueous extraction solvent can be neutral or acidic. Prior to the extraction step, the pH of the aqueous extraction solvent can be greater than about 1. Prior to the extraction step, the pH of the aqueous extraction solvent can be between about 5 and about 8.

Gold in the acid lysate can be present as Au (III). Gold in the acid lysate can exist as an Au (III) complex. This can exist as AuCl ₄ ⁻ (eg, HAuCl ₄ ).

  The method can include reducing gold in the aqueous extract to Au (0). The method can include reducing gold in the aqueous extract to Au (0) and separating gold metal (Au (0)) from the aqueous extract. The method may include the step of further refining Au (0).

  The method can also include recovering alcohol from the alcohol extract. The recovered alcohol can be reused in step (a). This can be reused as the extraction solvent in step (a).

In one aspect, a method for recovering gold is provided comprising the following steps:
Dissolving a copper anode slime using an acid and an oxidant to provide an acid lysate;
Selectively extracting an acid lysate with an alcohol having low miscibility with water to form an alcohol extract containing gold;
-Recovering gold from the alcohol extract.

In another embodiment, a method for recovering gold is provided comprising the following steps:
Dissolving copper anode slime using concentrated mineral acid and oxidant to provide an acid lysate;
Selectively extracting an acid lysate with an alcohol having low miscibility with water to form an alcohol extract containing gold;
Extracting gold from the alcohol extract into an aqueous extraction solvent having a pH above about 1.

In another embodiment, a method for recovering gold is provided comprising the following steps:
Dissolving copper anode slime using concentrated hydrochloric acid and hydrogen peroxide to provide an acid lysate having a hydrochloric acid concentration of about 3N to about 5N;
Selectively extracting an acid lysate with an alcohol to form a gold-containing alcohol extract, the alcohol comprising 2-ethyl-1-hexanol, 8-methyl-1-nonanol, and A process selected from the group consisting of mixtures thereof;
Extracting gold from the alcohol extract into an aqueous extraction solvent having a pH greater than about 1.

In another embodiment, a method for recovering gold is provided comprising the following steps:
Dissolving copper anode slime using concentrated hydrochloric acid and hydrogen peroxide to provide an acid lysate having a hydrochloric acid concentration of about 3N to about 5N;
Selectively extracting an acid lysate with an alcohol to form a gold-containing alcohol extract, the alcohol comprising 2-ethyl-1-hexanol, 8-methyl-1-nonanol, and A process selected from the group consisting of mixtures thereof;
Scrubbing the alcohol extract with dilute hydrochloric acid; and extracting gold from the alcohol extract into an aqueous extraction solvent having a pH greater than about 1.

In another embodiment, a method for recovering gold is provided comprising the following steps:
Dissolving the copper anode slime at a temperature above about 85 ° C. using concentrated hydrochloric acid and hydrogen peroxide to provide an acid lysate having a hydrochloric acid concentration of about 3N to about 5N;
Selectively extracting an acid lysate with an alcohol to form a gold-containing alcohol extract, the alcohol comprising 2-ethyl-1-hexanol, 8-methyl-1-nonanol, and A process selected from the group consisting of mixtures thereof;
Scrubbing the alcohol extract with dilute hydrochloric acid;
Extracting gold from the alcohol extract into an aqueous extraction solvent having a pH greater than about 1, and reducing the gold in the aqueous extraction solvent to gold (0).

  The present invention also provides gold in the form of Au (0) (gold metal) recovered by the method of the first aspect. The gold metal may have a purity greater than about 99.9% by weight.

  In a second aspect of the invention, the use of a primary alcohol to extract a denomination from an acid lysate of copper anode slime is provided. The primary alcohol can be a branched chain alcohol. The branched chain alcohol may comprise 2-ethyl-1-hexanol, 8-methyl-1-nonanol, or a mixture thereof.

The preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings.
Flow diagram for wet refining process for recovering gold from anode slime. Flow diagram for gold solvent extraction process for anode slime lysate. Flow diagram for wet process to recover various elements from anode slime.

  The present invention relates to a gold solvent extraction step of a gold recovery method. An example of a preferred overall process flow diagram is shown in FIG. One use of this method is to achieve effective control of radioactivity. This specification describes a solvent extraction process for recovering gold from copper anode slime liquor resulting from wet chlorination leaching. Steps prior to and subsequent to solvent extraction, such as copper removal, silver recovery, selenium recovery, and copper anode slime dissolution in hydrochloric acid in the presence of a suitable oxidizing agent are conventional and well known in the art. . These unit processes can be used in combination with the gold solvent extraction method of the present invention in various ways.

The filtrate from the oxidative chloride leaching test can be used as a feed to the solvent extraction process described herein. A flow diagram of the method according to the invention is schematically shown in FIG. Gold species are extracted from a chloride-containing acid lysate solution into a solvent phase containing an active reagent that selectively targets gold. Thus, the solvent can be considered an active reagent or an active solvent or a selective solvent. Alcohols can react with gold-containing species (eg, by solvation) to form gold complexes or gold species. An example of such a complex is HAuCl ₄ -alcohol. Alcohols can solvate species that can contain gold (which can be complex). The solvent can be selective for gold and can eliminate impurities commonly present in such liquids under the conditions used in extraction (acidity, alcohol). Importantly, the solvent can eliminate radioactive impurities such as polonium-210, or can eliminate most of the radioactive impurities such as polonium-210 present. Also, the solvent is more sensitive to the denomination in the acid solution than the selenium, tellurium, copper, zinc, lead, bismuth, antimony, tin, arsenic, nickel, palladium, and platinum species in the acid solution. May be at least partially selective. To further control / remove impurities from the solvent, scrubbing the solvent phase with a separate aqueous solution may be necessary. The loaded solvent is then transferred to a back-extraction circuit that re-extracts the gold into the aqueous solution. This gold-rich back extract can be processed by reductive precipitation in a separate step. The back-extracted solvent may be returned to the extraction circuit and reused. The inventors have shown that such a process can improve from a solution with a gold to impurity ratio of <2% to a gold product of> 99.9%, which can be in the form of a denomination or a gold complex. . Two main solvents / reagents are used for this purpose. They are 8-methyl-1-nonanol, commonly known as isodecanol, and 2-ethyl-1-hexanol, also known as isooctanol. These solvents have the following advantages:
Low solubility in aqueous phase Good phase separation properties Can be back extracted into aqueous solution and thus can separate solvent extraction step and gold precipitation / recovery step Back extraction into aqueous solution at room temperature Can be back-extracted with water. Selective for gold over all major impurities present in the liquid, such as Po-210, Bi-210, and Pb-210. is there.

  Other solvents exhibiting the above properties may be used in the present invention.

  Surprisingly, certain alcohols can selectively extract gold (denomination) from an acid lysate of copper anode slime, and in particular can eliminate radioactive elements such as Po-210, Found by the inventor. Suitable alcohols are those that have a relatively low solubility / miscibility with respect to the acid lysate. This can be characterized by a relatively low solubility or miscibility in water or acid lysates. Preferably, its solubility in water (or acid lysate) is less than about 0.2 w / w%, v / v%, or w / v%, or about 0.15, 0.1, 0.09, or 0.08% at 20 ° C. Can be less. Its solubility in water can be, for example, about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, or 0.2%. The alcohol may have at least about 7 carbon atoms, or at least about 8, 9, or 10 carbon atoms, alternatively from about 7 to about 14 carbon atoms, or from about 7 to 12, 7 to 10, 8-12, 10-12, 10-14, or 8-10 carbon atoms, for example, about 7, 8, 9, 10, 11, 12, 13, or 14 carbon atoms Can have. This can be a linear alcohol. This can be a branched chain alcohol. This can have an alicyclic group. This can include one or more double bonds. The alcohol may contain one or more triple bonds. The alcohol may be liquid at 20 ° C. A mixture of alcohols may be used. The mixture of alcohols can be liquid at 20 ° C. Each alcohol in the mixture can independently be as described above. Suitable alcohols include 2-ethyl-1-hexanol and 8-methyl-1-nonanol. Tridecyl alcohol or a mixture containing tridecyl alcohol can also be used. These alcohols have the advantage of being relatively inexpensive and relatively freely available.

  The solubility of 2-ethyl-1-hexanol in water is reported to be 0.07% at 20 ° C. This is advantageously comparable (ie, substantially lower) to dibutyl carbitol, which has been reported to have a solubility of 0.3% at 20 ° C.

  The extraction solvent used in step (a) of the first aspect of the invention (i.e., the liquid used to selectively extract the acid lysate to form the alcohol extract) is as described above. May comprise an alcohol or a mixture of alcohols. This may consist essentially of the alcohol or mixture of alcohols. This may consist of said alcohol or a mixture of alcohols. The extraction solvent can include a diluent. The alcohol or mixture of alcohols can be soluble or miscible with the diluent. Thus, the extraction solvent may consist of or consist essentially of a mixture of alcohol (or a mixture of alcohols) and a diluent. The mixture of alcohol (or mixture of alcohols) and diluent can be liquid at 20 ° C. The diluent can be an inert diluent. The diluent may not be capable of selectively extracting gold from the acid lysate in the absence of an active or selective extraction solvent such as the alcohols described above. This may be a hydrocarbon diluent. This may be an aromatic hydrocarbon diluent. This may be an aliphatic hydrocarbon diluent. This may be a mixture of aromatics and aromatic hydrocarbons. This may be a kerosene based diluent. The kerosene-based diluent can have various aromatic content, paraffin content, and naphthene content. The diluent may be (or may include) any other type of inert diluent. The diluent may represent between about 10 to about 95% of the extraction solvent, or about 10-50, 10-20, 20-95, 50-95, 70-95, 90 by weight or volume. May correspond to ~ 95, 20-80, 30-70, 40-60, 20-50, 25-95, or 50-80%, e.g., about 10, 15, 20, 25, 30, 35, It may correspond to 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 80, or 95%.

  In step (a), the volume ratio of extraction solvent to acid lysate can be between about 0.1 and about 10, or about 0.1-5, 0.1-2, 0.1-1, 0.1-0.5, 0.1-0.2, Between 0.3-0.5, 0.5-10, 1-10, 2-10, 5-10, 0.5-5, 0.5-2, 0.5-1, 1-5, or 1-2, for example, about 0.1, 0.2, Can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, or 10, or some Other suitable ratios may be used. Generally, gold is concentrated in the solvent phase. Accordingly, the ratio of extraction solvent to acid lysate is preferably less than about 1, for example about 0.1 to about 1. The extraction solvent includes an amount of alcohol sufficient to complex substantially all of the gold present in the acid lysate (eg, at least about 80, 85, 90, 95, or 99%). It can be used in sufficient quantity. The alcohol in the extraction solvent is at least about 1, or at least about 1.1, 1.2, 1.3, 1.4, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 10, 20 to gold in the acid lysate. , 50, or 100 molar ratios. The methods described herein include at least about 80% of the gold present in the acid lysate, or at least about 85, 90, 95, 96, 97, 98, or 99% thereof, or about 80 to about 99 thereof. %, Or about 80-95, 80-90, 85-99, 90-99, 90-95, or 95-99% thereof may be recoverable. This may be able to recover about 80% of the gold present in the acid lysate, or about 85, 90, 95, 96, 97, 98, or 99% thereof. For example, it may be possible to recover at least about 90% of the gold in the acid lysate in a form of at least about 99% purity on a weight or molar basis. The reagent concentration and / or solvent to water ratio can be adjusted to extract the desired proportion of gold (described above).

  Therefore, the method of the present invention includes a first step of selectively extracting the acid lysate of copper anode slime with the above-described extraction solvent. Gold is then recovered from the resulting alcohol extract. The recovered gold may be metallic gold, or a gold compound or complex. The acid lysate may be an aqueous acid lysate.

  The acid solution can be obtained by dissolving the gold-containing copper anode slime using an acid. A concentrated mineral acid can be used for the dissolution. A preferred acid is hydrochloric acid. The acid concentration can be at least about 5N, or at least about 6, 7, 8, 9, or 10N. This can be, for example, 5, 6, 7, 8, 9, 10, 11, or 12N. The acid has a final acid concentration between about 3-6N, or about 3-5N, 3-4N, or 4-5N, such as about 3, 3.5, 4, 4.5, 5, 5.5, or 6N. It may be combined with the liquid in a ratio sufficient to achieve. The dissolution can be viewed as gold extraction or leaching from the copper anode slime. The acid used for this can be regarded as a leachate or a digesting mixture. The gold-containing copper anode slime can include gold in an oxidation state of less than 3, for example, oxidation state 0 or 1. This can include more than one denomination. This may include one or more Au (0) species and one or more Au (I) species. This may include gold in a form that can be oxidized to Au (III). This may include gold in the oxidation state 3 (ie, Au (III)) in addition to or instead of gold in the oxidation state 3.

  The acid used to dissolve the gold-containing anode slime can include an oxidizing agent. Suitable oxidizing agents include hydrogen peroxide and chlorine. The oxidizing agent can be, for example, about 5 to about 27M, or about 5 to 20, 5 to 10, 10 to 20, 20 to 27, or 10 to 15, for example about 5, 6, 7, 8, 9, 10 , 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, or 27M can be added to the acid (or anode slime) as a concentrate . The oxidant can be an oxidant that is strong enough to allow any gold present in the slime to be oxidized to Au (III) in an oxidation state of less than +3. The oxidant is in a molar excess (eg, 10%, 20%, 50%, or 100%) than the amount required to oxidize any gold present in an oxidation state of less than +3 to Au (III). % Excess). The amount of oxidant used may need to take into account the oxidation of other elements present in the slime as well. The dissolving step can include heating the anode slime, optionally with an acid containing an oxidizing agent. The heating can be performed to a temperature suitable for dissolving the gold in the anode slime in the acid and for a suitable period of time. At least about 90% of the gold may be dissolved in the acid, or at least about 91, 92, 93, 94, 95, 96, 97, 98, or 99% of the gold may be dissolved in the acid. The temperature may be the reflux temperature of the acid. This may exceed about 70 ° C, or may exceed about 75, 80, 85, 90, or 95 ° C. This is between about 70 and about 110 ° C., or about 70 to 100, 70 to 90, 80 to 110, 90 to 110, or 90 to 100 ° C., for example, about 70, 75, 80, 85, 90, 95 , 100, 105, or 110 ° C. A suitable temperature is about 96 ° C. Suitable times for lysis are at least about 1 hour, alternatively at least about 2, 3, or 4 hours, alternatively about 1-10, 1-5, 1-2, 2-10, 4-10, 3-8 , Or 3-5 hours, for example, about 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 hours.

  If both acid and oxidant are used in the dissolution of the copper anode slime, it is readily understood that these may be added separately to the slime or may be combined and then added to the slime. Will.

  The resulting acid lysate is at least about 1 g / L, alternatively at least about 2, 3, 4, or 5 g / L, alternatively between about 1 and about 40 g / L, alternatively about 1-20, 1-10, 1-5, 5-40, 10-40, 20-40, 5-20, or 5-10 g / L, e.g. about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, It can have a gold concentration of 15, 20, 25, 30, 35, or 40 g / L.

  Prior to extraction with alcohol, the acid lysate may be diluted to achieve the desired acid concentration. As noted elsewhere, the desired acid concentration can be from about 3N to about 6N.

  Thus, the step of dissolving the gold-containing copper anode slime using acid to provide an acid solution can include dissolving the anode slime in the dissolving mixture, the dissolving mixture being concentrated. Acid (eg, hydrochloric acid) and an oxidizing agent (eg, hydrogen peroxide). This may include heating the anode slime in the dissolving mixture. This can include heating the anode slime in the dissolution mixture at a temperature and for a period sufficient to dissolve at least about 90% of the gold in the anode slime. This additionally adds the resulting acid lysate between about 3N and about 6N (alternatively about 3-5N, 3-4N, 4-6N, 5-6N, or 4-5N, e.g. about 3 , 4, 5 or 6N).

  The method is suitable for selectively extracting gold from copper anode slime or decoppered anode slime, but also for extracting gold from other liquids or aqueous solutions with a low gold to total metal ratio. Can be used. In particular, the method may be able to separate gold from the acid lysate of radioactive anodic slime and thus be able to separate gold from the radioactive. Radioactivity may be present in the acid lysate in the form of one or more radioisotopes, eg, polonium-210, lead-210, bismuth-210, and the like. The method extracts less than about 10% or less than about 5, 2, 1, 0.5, 0.2, or 0.1% of the radioisotopes present in the acid lysate (or each radioisotope independently) Can do. The method includes a small percentage of gold to metal, metalloid, and / or metalloid in the acid lysate, i.e. less than about 50% by weight or mole, or about 40, 40, 20, 10, 5, Or is particularly suitable for selective extraction of gold from an acid lysate that is 2%. Gold is about 0.01 to about 50% or about 0.01 to about 20% of metal, metalloid, and / or metalloid, or about 0.01 to 10, 0.01 to 5, 0.01 to 2, 0.01 to 1, 0.1 to 20, 0.5 Equivalent to ~ 20, 1-20, 5-20, 10-20, 1-20, 5-20, 10-20, 1-10, 1-5, 1-2, 2-5, or 5-10% Can do. This is about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4 of metals, metalloids, and / or metalloids in acid lysates. , 4.5, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, or 50%. Other elements that may be present in the acid solution include selenium, tellurium, silver, copper, zinc, lead, bismuth, antimony, tin, arsenic, nickel, palladium, and platinum. They can be present in the acid lysate in a form that cannot be extracted into alcohol or in a form that can only be extracted to a limited extent. An analysis of a typical copper smelting slime is shown below.

(Table 1) Typical copper refining slime composition range {(according to Hoffmann, JE, The World's Most Complex Metallurgy-Revisited. Proceedings of European Metallurgical Conference EMC 2007, Vol. 2, pp. 555-570}

  There are a wide variety of chemical forms of these and other elements present in the slime obtained by electrolysis of copper.

Only a small amount of gold and silver released during the copper electrorefining process appears in the residue as very small metal particles. Gold has a strong affinity for selenium and nucleates on Ag-Se selenide inclusions. Another part of the gold dissolves in the sulfate solution during the refining process and later precipitates with the silver as a minor component of the oxidate phase. Most of the gold appears in a discontinuous Ag—Au—Cu selenide phase (eg, Ag _2−x Au _x Se, which is in the form of intermetallic AgAuSe).

Silver derived from the copper anode is somewhat soluble in acidic electrolyte solutions. Some of this dissolved silver reacts with copper selenide, Cu ₂ Se, and separate and intermetallic Ag—Cu and Ag—Au selenide species (eg, silver selenide Ag ₂ Se and silver copper). (I) AgCuSe) which is a selenide is formed.

Like Se, tellurium binds preferentially to Au and Ag and is primarily in the Cu-Ag selenide-telluride phase, as well as other individual and intermetallics such as Ag ₂ Te, Au ₂ Te, etc. In the form of tellurides.

In addition, during the electrolysis process, arsenic, antimony, and bismuth dissolve and a very small amount of metal precipitates as Pb-Sb-As-Bi oxide. Lead is also detected in the form of lead sulfate PbSO ₄ .

Precipitated copper exists in many forms, and mainly as an intermetallic compound chalcogenide, for example, AgCuSe, which is a copper silver selenide, Cu _2-x Se _x, which is a copper selenide (wherein x ≦ x 1), Cu ₂ Te, which is a copper telluride, and Cu ₂ S, which is a copper sulfide. Copper also appears in the oxidation product phase and is found in the sulfate or arsenate form.

  The extraction of step (a) of the method may include batch extraction, such as repeated batch extraction. This may include continuous extraction, for example continuous countercurrent extraction. There may be one countercurrent extractor. There may be more than one countercurrent extractor, eg, 2, 3, 4, 5, or 6 or more countercurrent extractors. For two or more countercurrent extractors, in some operating modes, fresh extraction solvent used in the final extractor may be included, and the extraction solvent passes through a series of extractors in the opposite direction to the acid lysate. This is passed through from the last to the second extractor and then to the first extractor.

The extraction solvent used in the present invention is selective for the denomination in the acid lysate. Gold can be present in the acid lysate as a gold complex prior to extraction. The gold complex can be a gold (III) complex. This can be a gold halide complex. This can exist as AuX ₄ ⁻ , where the halogen is, for example, chlorine, bromine, or iodine (or a mixture of two or more thereof). This can exist as AuCl ₄ ⁻ . The extraction solvent can be selective for the gold complex. Gold is at least about 70%, or at least about 75, 80, 85, 90, or 95%, eg, about 75, 80, 80, on a weight or molar basis, based on the total amount of metals, metalloids, and metalloids in the extract , 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, or 99% present in the alcohol extract may be sufficiently selective.

  However, it will be appreciated that in some cases, a higher purity may be required than provided in the extraction process. In this case, the method may include scrubbing the extract with a scrubbing agent to remove impurities from the extract. A suitable scrubbing agent is a dilute mineral acid. The dilute mineral acid may comprise the same mineral acid used to dissolve the anodic slime or may comprise a different mineral acid. This may include a mixture of mineral acids. This can be, for example, dilute hydrochloric acid. The dilute mineral acid may be about 0.01-4N mineral acid, or about 0.01-3, 0.01-2, 0.01-1, 1-4, 1-4, 1-3, 0.5-2, 0.05. ~ 1, 0.1-1, 0.5-1, 0.01-0.5, 0.01-0.1, 0.01-0.05, 0.05-0.5, or 0.05-0.2, for example, about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, or 4N It may be an acid. Scrubbing can include extraction of an alcohol extract with a scrubbing agent. This can be carried out in a continuous countercurrent manner or in a batch manner. By the scrubbing, the percentage of gold in the alcohol extract is at least about 90%, or at least about 95 or 99%, for example about 90, 91, 92, 93, as a percentage of total metals, metalloids and metalloids. 94, 95, 96, 97, 98, or 99%. The scrubbing agent may be at least partially selective for metals other than gold.

  Gold can be obtained from an alcohol extract, optionally from a scrubbed alcohol extract, by extraction with an aqueous extraction solvent. The aqueous extraction solvent can have a pH greater than about 1. This can be near neutral pH. The pH of the aqueous extraction solvent can be a pH greater than about 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, or 7. This is about 1-8, 1-7, 1-5, 1-3, 1-2, 2-8, 4-8, 6-8, 7-8, 2-3, 3-4, 4- May be 5, 5-7, or 6-7, for example about 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, or 8 . The aqueous extraction solvent can be a dilute acid, such as dilute hydrochloric acid. The dilute acid is between about 0.01 and about 0.1 N, or between about 0.01 and 0.5, 0.5 to 0.1, 0.02 to 0.08, 0.03 to 0.07, or 0.04 to 0.06, such as about 0.01, 0.02, 0.03, 0.04, It can be 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1N. The aqueous extraction solvent can be water. The water can be at least about 99% pure, or at least about 99.5 or 99.9% pure.

  Any or all of the extraction steps described above can be independently performed at room temperature or some other convenient temperature. The temperature can be, for example, about 10 to about 30 ° C., or about 10-20, 20-30, or 15-25 ° C., such as about 10, 15, 20, 25, or 30 ° C., or in some cases It can be carried out at some other temperature, for example 35, 40, 45, 50, 55, or 60 ° C.

  As an alternative to obtaining gold from the alcohol extract by extraction, gold may be obtained from the alcohol extract by direct reduction. This can be achieved, for example, by treating the gold-containing alcohol extract with a reducing agent such as oxalic acid.

  The method can include reducing gold in the aqueous extract to Au (0). Au (0) can be in the form of metallic gold. Such reduction is well known in the art. The reduction can include reacting gold in the aqueous extract with a reducing agent. Suitable reducing agents include sulfur dioxide, sulfite, oxalate, and oxalic acid. The method may further comprise the step of refining Au (0). Such methods are also well known in the art and include, for example, the Miller process (passing chlorine gas through molten gold) and electrolytic purification. The step of reducing gold to Au (0) may provide further purification (ie, removal of impurities such as non-gold metals, metalloids, and / or metalloids). Thereby, the purity of the gold is greater than about 99% on a weight or molar basis, or at least up to about 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, 99.8, or 99.9%, for example, about 99, 99.1, 99.2, It can be up to 99.3, 99.4, 99.5, 99.6, 99.7, 99.8, 99.9, 99.91, 99.92, 99.93, 99.94, 99.95, 99.96, 99.97, 99.98, 99.99, 99.995, or 99.999%.

  The denomination in the aqueous extract may be further purified prior to reduction and (optional) further refining. This can include, for example, acidification of an aqueous extract (as described above for anodic slime) and extraction of gold into an organic extraction solvent. The organic extraction solvent should be selective for gold. Suitable organic extraction solvents for this purpose are alcohols used as extraction solvents for the original acidic liquid. The resulting organic extract can then be re-extracted into an aqueous extraction solvent (optionally the same as described above for the extraction of the alcoholic extract of the acid lysate) and the resulting Gold can be recovered from the aqueous gold solution.

  The methods described herein can reduce the gold residence time over conventional methods. The residence period is defined as the period necessary for the gold-containing feedstock introduced into the process to become a product. In continuous extraction processes such as those described herein where gold is dissolved at the beginning of the process and then continuously fed to the extraction circuit, the residence time of the gold is much longer than other processes. The residence time of gold in the method of the present invention can be between about 1 and about 10 days, but can be longer or shorter than this range. The residence time of gold is about 1-7, 1-5, 1-3, 3-10, 5-10, or 5-8 days, for example, about 1, 2, 3, 4, 5, 6, 7, It can be 8, 9, or 10 days.

  The gold metal provided by the methods described herein is greater than about 99% by weight or molar basis, or at least about 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, 99.8, or 99.9% purity, For example, having a purity of about 99, 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, 99.8, 99.9, 99.91, 99.92, 99.93, 99.94, 99.95, 99.96, 99.97, 99.98, 99.99, 99.995, or 99.999% Can do.

The overall process suitable for gold recovery is shown in FIG. The method of the present invention mainly relates to the right part of FIG. Advantages of the recovery process using oxidative chlorination of decopperized slime as illustrated in FIG. 3 over the conventional recovery process include the following:
・ Simple, compact and efficient;
・ Reduction of labor costs;
• Usually cheaper and more productive than conventional purification methods;
-Recover metal in high yield;
Better separation of elements extracted from anode slime and thus
-Producing metals with significantly reduced impurity concentration;
-Avoid unwanted circulation of residues from the process;
Avoiding high-temperature treatments (e.g. smelting) that lead to the release of harmful substances (e.g. selenium and lead) into the atmosphere and thus
-Avoid costly reuse of secondary slag and revert;
-Significantly increase occupational safety and working conditions;
-Better for the environment;
-Significantly reduce gold and silver (residence) period;
・ In-process inventory is greatly reduced.

  The following are specific examples demonstrating the application of a gold solvent extraction process to recover and purify gold from copper anode slime. The SX process is incorporated into a flow sheet that uses oxidative chloride leaching of decopperized slime. A simplified flow sheet is shown in Figure 1.

Pretreatment of anode slime The copper anode slime contains Cu, Au, Ag, Pb, Se, Te, Sb, Ni, As, and Bi as main components. The composition of the copper anode slime can vary substantially for various plant operations, but is usually within the range shown in Table 2. Note that the Au concentration in the copper anode slime is up to 2%. Many other impurities are also present at low concentrations, including the presence of radionuclides such as Po-210. In making the solutions for the tests outlined below, copper anode slime with a composition within the range of typical copper anode slime but with a low Sb concentration was used.

Table 2 Typical composition of anode slime

The decoppered anode slime was treated by oxidative chloride leaching. This was typically done by adding concentrated HCl (12M) and H ₂ O ₂ (12.6M) to the decoppered slime. A temperature of 96 ° C. was maintained for 4 hours under reflux conditions. Very high dissolution of Au (> 98%) was achieved. Ag and Pb were eliminated to the residue and only <0.05% Ag and 6.7% Pb were entrained in the solution. The solubility of Se and Te was very high (> 98%). Significant dissolution of As, Bi, and remaining Cu also occurred. The resulting liquid contained 5-10 g / L Au.

Example 1 Selectivity of Reagent over Au over Po-210 In the following test, a leachate made from the oxidative chlorination of decopperized slime as described above was used. The leachate was diluted to about 160 mg / L Au in a series of solutions with various hydrochloric acid concentrations (1-8 M HCl). The solution was then contacted with the same volume of organic solution in a separation test. Two types of solutions were tested:
(i) 50% by volume of isodecanol (Exxal® 10) in Escaid 500 (hydrocarbon diluent with low aromatic content)
(ii) 50% by volume of 2-ethylhexanol in Escaid 500.
The extraction ratio of Au and Po-210 according to HCl concentration is shown in Table 3, but when the HCl concentration is adjusted between 3 and 5M, the proportion of Po-210 eliminated to the residue increases and Au extraction It can be seen that the rate is high.

Table 3 Typical composition of anode slime

Example 2 Au Recovery and Purification by Solvent Extraction A leachate obtained from the oxidative chlorination of decoppered anode slime containing 4.1% Au to cation in solution was tested as follows. The leachate was contacted in an organic solution containing 50% by volume of isodecanol in Escaid 300 diluent in a four-stage extraction in batch countercurrent mode. Five cycles were performed to ensure that equilibrium was reached. An A: O ratio of 4.5 (ie leachate to organic solution) was used. The feed to the solvent extraction process contained 6.5 g / L Au and the resulting gold rich organics contained 30.3 g / L Au. > 96% gold was extracted. Analysis of gold-rich organics is shown in Table 4, which shows that Au has improved from 4.1% to 82% over the main impurities, Se, Te, As, and Sb. The gold-rich solvent was subjected to an additional 7-step counter-current scrubbing with hydrochloric acid solution, which further improved Au to 93%. The scrubbed solvent was back extracted with dilute hydrochloric acid solution (0.05N) to produce a gold rich back extract. Au was precipitated directly by adding sodium oxalate to the gold rich back extract, resulting in a 99.9% pure Au product.

Table 4 Purification of Au using solvent extraction

Claims (29)

A method of recovering gold from an acid digest of gold-containing copper anode slime,
(a) selectively extracting the acid lysate with an alcohol having low miscibility with water to form an alcohol extract containing gold;
(b) recovering gold from the alcohol extract, wherein the gold in the acid lysate is in a form that can be extracted into the alcohol.   The method of claim 1, wherein the alcohol has a solubility of less than about 0.2 w / w%, v / v%, or w / v% in water at 20 ° C.   The method according to claim 1 or 2, wherein the alcohol is a primary alcohol.   4. The method of claim 3, wherein the primary alcohol is a branched chain alcohol.   5. The method of claim 4, wherein the branched chain alcohol is selected from the group consisting of 2-ethyl-1-hexanol, 8-methyl-1-nonanol, and mixtures thereof.   6. The method of any one of claims 1-5, comprising dissolving the gold-containing copper anode slime using an acid to provide an acid lysate.   The method of claim 6, wherein the dissolving step comprises combining anode slime and concentrated hydrochloric acid.   The method according to claim 6 or 7, wherein an oxidizing agent is used together with an acid in the step of dissolving the gold-containing copper anode slime.   The acid lysate contains a radioactive element, and the acidity of the acid lysate is such that at least about 90% of the gold present in the lysate is extracted into the alcohol and the radioactive element present in the acid lysate. 9. The method of any one of claims 1-8, wherein the acidity is such that less than about 10% of the amount is extracted into the alcohol.   10. The method according to claim 9, wherein the radioactive element is polonium.   11. The method according to any one of claims 1 to 10, wherein the ratio of gold to total metals in the acid solution prior to step (a) is about 4% or less per weight or mole.   12. A method according to any one of the preceding claims, wherein step (a) comprises continuous countercurrent extraction. 13. A method according to any one of claims 1 to 12, additionally comprising the following steps:
Scrubbing the extract to remove impurities from the alcohol extract, the step being performed between steps (a) and (b).   14. The method of claim 13, wherein the scrubbing step comprises scrubbing with dilute mineral acid.   15. A method according to any one of claims 1-14, wherein step (b) comprises extracting the alcohol extract with an aqueous extraction solvent to provide a gold-containing aqueous extract.   16. The method of claim 15, wherein the pH of the aqueous extraction solvent is greater than about 5.   17. A process according to claim 16, wherein the pH of the aqueous extraction solvent is approximately neutral.   18. A method according to any one of claims 15 to 17, comprising the step of reducing gold in the aqueous extract to Au (0).   19. The method of claim 18, further comprising refining Au (0).   20. A method according to any one of claims 1 to 19, wherein the gold in the acid lysate is present as Au (III). Gold acid lysate is AuCl ₄ ^- is present as a method of claim 20, wherein.   The method according to any one of claims 1 to 21, comprising the step of recovering alcohol from the alcohol extract.   23. The method of claim 22, wherein the recovered alcohol is reused in step (a).   24. Gold recovered by the method of any one of claims 1-23.   25. The gold of claim 24, having a purity greater than about 99.9% by weight.   Use of a primary alcohol to extract gold from an acid solution of copper anode slime.   27. Use according to claim 26, wherein the primary alcohol is a branched chain alcohol.   28. The use of claim 27, wherein the branched chain alcohol is selected from the group consisting of 2-ethyl-1-hexanol, 8-methyl-1-nonanol, and mixtures thereof.   9. The method of claim 8, wherein the oxidant is hydrogen peroxide or chlorine.

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