RU2115751C1 - Method of recovering precious metals - Google Patents

Abstract

FIELD: precious metal recovery. SUBSTANCE: method is designed for application when recovering precious metals from electronic industry wastes and from low-grade ores in presence of a protein-nature complexing agent. The latter is a fermentative hydrolyzate of the protein substances of industrial microorganism biomass having hydrolysis ratio at least 0.65 at amine nitrogen content 0.08 mol/l in 0.025-0.05 M hydrogen peroxide solution. EFFECT: increased degree of recovery and reduced power consumption. 1 tbl

Description

 The invention relates to methods for the extraction of precious metals (gold and silver) in the processes of their extraction from waste from the electronics industry and poor ores in the presence of protein-complexing agents.

 Currently, the most common way to extract gold and silver from ores is the cyanidation method - dissolving a metal in an alkaline solution of sodium cyanide with air access [1].

 A significant drawback of this method of dissolving precious metals is the toxicity of cyanide solvents and the inability to use the method for hard-to-initiate poor ores and waste from galvanic industries (electronic scrap).

 Another way to extract gold and silver in an aqueous solution is the microbiological method. The latter, as a rule, involves the treatment of metal-containing waste with a culture fluid obtained as a result of the cultivation of microorganisms producing amino acids [2].

 The disadvantage of this method is the need to maintain aseptic conditions.

The closest in technological essence and the achieved effect to the proposed method is the electrochemical method of dissolving gold [3], including the anodic polarization of gold-containing raw materials at an electrode rotation speed of 2 • 5 10 ^-3 V / s in an amino acid buffer solution at a concentration of 10 ^-2 - 10 ^{- 3} mol / L. Potassium monophosphate is used as a buffer. As an amino acid, histidine, cysteine, or glycyl-glycine dipeptide can be used.

 The disadvantages of this method are the low efficiency of the process due to the use of highly purified preparations of individual amino acids, the low dissolution rate of gold, as well as the low degree of metal extraction into the solution.

 The objective of the invention is to develop a less energy-intensive method for extracting precious metals into a solution, which allows to achieve a high degree of metal extraction.

 The problem is solved in that the method of processing gold and silver-containing raw materials is proposed to be carried out in the process of dissolution of precious metals in the presence of a complexing agent, which is used as an enzymatic hydrolyzate of protein substances of the biomass of industrial microorganisms having a degree of hydrolysis of at least 0.65 with an amine nitrogen content of 0 , 08 mol / L in 0.025 - 0.05 M hydrogen peroxide solution.

Gold and silver-containing waste is treated in 250 ml conical flasks, which are placed on a rocking chair at a rotation speed of 200 min ^-1 for 120 hours. A protein hydrolyzate containing 0.08 mol / l of amine nitrogen is used as a complexing agent, to which a solution is added hydrogen peroxide to a content of the latter of 0.15 mol / L. As a result, the degree of extraction of the precious metal into the solution is not less than 85% and the energy intensity of the process is reduced.

 Example (prototype). 100 ml of a 0.1 M sodium chloride solution are poured into a 150 ml cell and the hydrolyzate is added until the concentration of amine nitrogen is 0.04 mol / L. A hydrolyzate with a degree of hydrolysis of at least 0.65 is used. A gold-plated electrical contact is immersed in the solution. It maintains a potential of 1.2 V. The solution is stirred with a magnetic stirrer. After 120 hours of treatment, 35% of gold is recovered in the solution.

 Example 1. A 0.26 g gold-plated electrical contact is placed in a 250 ml rocking flask, 100 ml of a hydrolyzate solution containing 0.08 mol / L of amine nitrogen are added, and hydrogen peroxide is added to the content of 0.05 mol / L in the solution.

The flask is placed on a rocking chair at 25 ^o C and incubated for 120 hours. The degree of gold recovery is 85%.

 Example 2. The metal extraction is carried out according to example 1, but as a raw material use a silver-plated contact. Moreover, the degree of silver recovery is 80%.

 Example 3. The experiment is carried out as in example 1. As a raw material use a gold-plated contact. The concentration of hydrogen peroxide is 0.025 mol / L. The degree of extraction of gold in a solution of 45%.

 Example 4. The experiment is carried out as in example 1. As a raw material, a silver-plated electrical contact is used. The concentration of hydrogen peroxide is 62%.

 A comparison of the proposed method and the prototype are presented in the table.

Compared with the prototype method has the following advantages:
- the energy intensity of the process is reduced due to the use of hydrogen peroxide as an oxidizer (about 5-6 times);
- the degree of extraction of gold increases;
- simplified hardware design process.

Claims (1)

 A method of extracting precious metals from waste, including the dissolution of precious metals in the presence of a complexing agent of protein nature, characterized in that the dissolution of precious metals is carried out chemically using an enzymatic hydrolyzate of protein substances of the biomass of industrial microorganisms with a degree of hydrolysis of at least 0.65 in the presence of hydrogen peroxide with a concentration of 0.025 - 0.05 mol / L.

Images