RU2025514C1 - Method to extract precious metals from ores and concentrates - Google Patents

Abstract

FIELD: gold and silver extraction from ores or concentrates. SUBSTANCE: precious metals are leached out from ores or concentrates with 1 to 10 wt. per cent of free of cyanides aqueous salt solution, of 6 to 8 pH, in the presence of oxidant. Then the pulp is filtered, cake is washed with water, solution produced is concentrated and directed to leaching of a new batch of ore or concentrate. Gold and silver are precipitated with amine agent from the solution produced from pulp concentration. Then the gold and silver are filtrated. The solution is then recovered and also directed to leach ore or concentrate. EFFECT: reuse of agents.

Description

 The invention relates to environmentally friendly, low-waste hydrometallurgy of precious metals (gold and silver).

 A known method of extracting precious metals from ores or concentrates, including leaching of gold and silver from ore or concentrate with a saline aqueous solution in the presence of an oxidizing agent, filtering the pulp, washing the cake with water and precipitating gold and silver from the clarified solution.

The disadvantages of this method are the low technological capabilities, as well as the low leaching rate of gold and silver from ore or concentrate with a solution of cyanide salts (90-95% of Au recovery is achieved in more than 10 hours);
the difficulty of extracting gold and silver from arsenic and antimony ores or concentrates due to the formation of waterproof films on the surface of Au and Ag due to the high values of the hydrogen index of the cyanide solution (pH = 9-11), as well as contamination of the latter As and Sb, which significantly complicates water - and gas cleaning;
chemical hazard of cyanide solutions (hazard class I).

 The aim of the invention is the expansion of technological capabilities.

This is achieved by the fact that the leaching of gold and silver from the ore or concentrate is carried out with 1-10 wt.% - aqueous salt solution, not containing cyanide, with a pH of pH 6-8 in the presence of an oxidizing agent for at least 60 minutes, formed after washing caking salt water solution is concentrated and directed to the leaching of ore or concentrate, simultaneously with this gold and silver is precipitated from the clarified solution of the amine reactant at a temperature of 20-60 ^{° C} is separated from the solution by filtration, and the latter is regenerated, and also eg leaching ore or concentrate.

 The proposed method is implemented as follows.

 The crushed ore or concentrate is poured into an apparatus filled with 1-10 wt.% Aqueous saline, not containing cyanide solution at pH = 6-8.

 As a saline aqueous solution, a solution of potassium triodide (sodium) and potassium iodide (sodium) or potassium bromide is usually used. In some cases, in addition to the above components, sulfate and / or chloride and / or potassium (sodium) nitrate are added to the saline aqueous solution.

 The composition of the solution depends on the mineral composition of the ore or concentrate and the content of precious metals in them. The duration of the leaching process is at least 60 minutes and is carried out in stages 1-2.

The prepared pulp is mixed in the presence of an oxidizing agent J ₂ , Br ₂ or an ozone-air mixture, and then filtered. The cake is washed with water, the resulting saline solution is concentrated by evaporation, electrodialysis or ion-exchange sorption and sent to leach a new portion of the crushed ore or concentrate. From the resulting slurry by filtration amine reagent solution, such as diethylhydroxylamine, at 20-60 ^{° C} precipitated gold and silver. The precipitate with precious metals is filtered off, the filtrate is regenerated (by electrochemical or reagent method) and sent to leach the crushed ore or concentrate. The degree of extraction of precious metals is 95-99%.

PRI me R 1. In the reactor pour 5 wt.% - aqueous salt solution with pH = 6, containing: 4.5 wt. % potassium triodide (sodium) and potassium iodide (sodium), 0.5 wt. % sulfate and / or sodium chloride (ratio [K (Na) I ₃ ] / [K (Na) I] = 10 ^-2 ). Then telluride-selenium ore is poured with a gold content of 14 g / t and silver 25 g / t in such an amount that the ratio T: W is 1: 1.5. The resulting pulp is intensively mixed for 80 min in the presence of an oxidizing agent J ₂ or Br ₂ with a concentration of 0.05 wt.%.

 After leaching, the pulp is filtered, the cake is washed with water, the resulting saline solution is concentrated and sent again to leach the crushed ore, and the washed cake is dumped.

A solution formed during filtration, is heated to 20-60 ^{° C,} was added amine reactant therein, e.g. diethylhydroxylamine, until the solution concentration of 0.01 mol / L and at pH 9-11 for about 60-80 minutes and the precipitated gold silver.

 Then the silver-silver precipitate is separated from the solution by filtration, and the solution is regenerated and fed to the leaching of a new portion of the crushed ore or concentrate.

 The degree of extraction was 95-99%.

PRI me R 2. In the reactor, the pulp is prepared from a 10 wt.% Saline aqueous solution with pH = 7 and crushed quartz low sulfide ore with a gold content of 25 g / t and silver 100 g / t (T: W = 1: 1). The saline solution contains potassium (sodium) triiodide, potassium (sodium) iodide (ratio [K (Na) I ₃ ] / [K (Na) I] = 10 ^-2 ) and 2 wt.% Sodium nitrate.

 The resulting pulp is stirred for about 150 minutes while simultaneously bubbling an ozone-air mixture through it with an ozone content of ≈ 3 vol.%.

 Then the pulp is filtered and the cake is washed with water. The washings thus formed are concentrated, regenerated and reused in the leaching of the starting material. The washed cake is sent to the dump.

Concurrently the clarified solution obtained by filtering the slurry heated to 40-60 ^{° C,} was added amine reactant therein, e.g. diethylhydroxylamine, to a concentration in the solution 0.1 mole / L at pH = 9-14 deposited gold and silver, the precipitate of which is then filtered. The de-malted solution is regenerated and sent to ore leaching.

 The degree of extraction of gold and silver is 95-98%.

PRI me R 3. In the apparatus pour 10 wt.% - aqueous salt solution containing potassium triiodide and potassium iodide (with the ratio [KJ ₃ ] / [KJ] = 10 ^-3 ), as well as 2 wt.% sodium sulfate (pH = 6-8). Then, concentrate is poured into the apparatus (the gold content is approximately 400 g / t, and silver 50 g / t) in such an amount that the T: W ratio is 1: 2.

The prepared pulp is stirred for 180-200 min, in the presence of J ₂ or Br ₂ with a concentration of 1 wt.%. After leaching, the pulp is filtered, the cake is washed with water from the salt components of the leachate, and the resulting diluted aqueous solution is concentrated, regenerated and reused in the processing of the starting material (concentrate).

 Gold and silver from the clarified solution are recovered in the same way as in example 2.

 The degree of extraction of gold and silver is 95-99.8%.

Experimental studies have shown that
the rate of leaching of precious metals from ore or concentrate by the proposed leach is an order of magnitude higher than the cyanide process, therefore, when extracting precious metals from ores or concentrates, the proposed method requires significantly lower capital costs;
during leaching of arsenic and antimony ores, the formation of water-soluble compounds of As and Sb is not observed, which greatly simplifies the subsequent measures for water and gas purification;
chemical hazard class of reagents III-IV used in the process, therefore, the risk of personnel work during maintenance of this process is reduced and its environmental hazard is reduced;
the regeneration of a saline aqueous solution allows the low-waste process of the proposed process.

 Thus, the proposed method is simpler, efficient, technologically advanced, as well as environmentally friendly and low-waste.

Claims (1)

METHOD FOR REMOVING PRECIOUS METALS FROM ORES AND CONCENTRATES, including leaching of gold and silver from ore or concentrate with a saline aqueous solution in the presence of an oxidizing agent, filtering the pulp, washing the cake with water and precipitating gold and silver from solutions, characterized in that the leaching of gold and silver from ore or the concentrate is carried out with a 1-10% iodine-containing saline aqueous solution at pH 6-8 for at least 60 minutes; the saline solution obtained after washing the cake is concentrated and sent to the ore leach or concentrate That, while gold and silver from solutions precipitated with an amine reagent at 20 - 60 ^o C, separated from the solution, the latter is regenerated and sent to the leaching of ore or concentrate.