BG61002B1 - Method for the extraction of precious metals from oxide ores - Google Patents

Abstract

The method is used in biohydrometallurgy. It increases the velocity and degree of extraction of precious metals from ores using low reagent consumption, It is safe for the service staff and the environment. By the method the ores are lyed using aqueous solution of thiosulphate and copper ions. The solution additionally contains amino acids of microbic origin having the following concentrations of the individual components, in g/l: thiosulphate from 10 to 200, cupric ions from 0.2 to 5 and amino acids of microbic origin from 0.5 to 5. The solution pH is weak alkaline, usually within 8-9. Hydrolysate of biomass of Saccharomyces lactis is used as a source of amino acids which is a by-product in the production of the enzyme superoxidedysmutase. The production solutions after lying are treated for most efficient the extraction of the dissolved precious metals by cementation with the metallic zinc.

Description

The invention relates to a method for the extraction of precious metal ores, which is used in bio-hydrometallurgy.

BACKGROUND OF THE INVENTION

The known methods can be divided into three groups: chemical, biological and chemico-biological. A common feature of these methods is that they are based on leaching of ores with solutions containing chemical and / or biological oxidants and complexing agents with respect to native gold and silver. The oxidants bring the native precious metals into ionic form, and the complexing agents bind them to stable complexes.

The most widespread of this type of methods is the cyanide method (1) in which the precious metal oxidation is carried out in an alkaline medium (most commonly molecular oxygen), the resulting ions being bound to water-soluble cyanide complexes by means of the leachable solutions cyanides are most often used with NaOH and Ca (Cl) ₂ and sometimes KCH. The reduction solutions are treated by various methods (sorption with activated carbon, ion exchange resins, zinc cementation) to extract the precious metals from the complexes. A major drawback of this method is the high toxicity of cyanide and the resulting environmental problems.

Also known is a chemical method for leaching precious metals by solutions of thiosulphate as a complexing agent (2). This method is applied in various embodiments, the most suitable of which is characterized by the presence of copper and sulphite ions in the leach solution (3), which play a role in the oxidation and complexation of precious metals and the stabilization of thiosulphate. The disadvantages of the process are the relatively narrow zone of stability of the thiosulphate complexes with gold and silver, the difficult oxidation of these metals in alkaline environment due to their high corrosion potential and the absence of suitable oxidants, the decomposition of thiosulphate, especially in the low ratio of the concentration of this ion that of the copper ions in the leach solution.

Biological methods are characterized by the development of appropriate microorganisms in the presence of leached ores, the noble metals being extracted as a result of the action of secreted microbial metabolites of different nature. The most useful is the use of certain heterotrophic bacteria (mainly Vaschis), which, when grown in a nutrient medium containing a suitable organic source of carbon and energy (sugars, proteins, etc.), secrete two types of metabolic products: , oxidizing native precious metals to ionic form, and amino acids linking dissolved metals to stable complexes (4). In these cases, the nutrient medium acts as leachable solution. A major drawback of this type of impacts is the inability to perform efficiently under real industrial conditions in which the beneficial microflora is wholly or partly displaced by different contaminants at the expense of both the original organic carbon source and energy in the environment, secreted amino acids. In addition, leaching can be performed in the relatively narrow physiological range of the basic physico-chemical parameters, and the rate and rate of extraction of noble metals are generally not high.

Combined chemical-biological methods are characterized by the use of various chemical reagents and microbial metabolites in a variety of combinations and ratios. The most suitable in this respect of noble metals / potassium permanganate, various peroxides, the oxon reagent, etc. and microbial culture liquids containing secreted amino acids or protein hydrolysates obtained after hydrolysis of microbial biomass. Especially efficient from an economic point of view is the use of biological solutions which are waste from various biotechnological processes, for example acidic hydrolyzate from yeast biomass of the genus Phytase tetraphagas gypsum (cytochrome C) waste, acidic yeast hydrolyzate of yeast biomass 8ассЬаготусез

/ RTI > / waste from production of the enzyme superoxide dismutase / etc. The pH of these solutions is brought to a weakly alkaline region (typically within the range of B-10) where the complexes of gold and silver with the amino acids are most stable, and then the chemical oxidant of these metals is added. Leaching with the so-prepared solutions can be carried out as a fine-grained ore in mechanically stirred reactors, or with a coarse ore in chalky of a suitable shape and size. Production solutions containing dissolved precious metals are processed efficiently by zinc cementation, but the other conventional methods (activated charcoal, ion exchange) can also be used.

Disadvantages of this method are the notably high rate of extraction of noble metals from ores (commensurate with cyanation), the irrational consumption of oxidants and complexing agents (due to the partial decomposition of the amino acids from the added chemical oxidizers), as well as the notably high stability of the precious metals complexes with amino acids.

SUMMARY OF THE INVENTION

The problem solved by the invention is related to the provision of high speed and degree of gold and silver extraction using low-cost, affordable reagents that are not toxic to service personnel and the environment.

The method for extracting precious metal from ores consists of leaching the ores with a solution of an alkaline pH (typically in the range 8-9), in which the role of oxidizing native precious metals is performed by the dissolved molecular oxygen and cupricones, but as a complexing agents for solubilized gold and silver use thiosulphate and amino acids of microbial origin. The optimal concentrations of the reagents used are influenced to a certain extent by the composition and structure of the leached ores, but are generally in the range of: for cuppers / casting in the form of SiO _{4 (} 0.5 H ₂ O) - from 0.2 to 5/1 for thiosulphate / (in the form of the ammonium salt), from 10 to 200 g / l, for a total amino acid concentration of 0.5 to 5 g / l. As an amino acid source, acid hydrolyzate from yeast Saccharomyces cerevisiae, neutralized with sodium hydroxide, is particularly suitable. This hydrolyzate is a waste from the production of the enzyme superoxide dismutase.

The leaching of the said solution can be carried out in both chalds formed of ore of a suitable size (usually 15 mm) and in mechanically stirred reactors in which leached ore (usually 0.1 mm / . The optimum leaching temperature is in the range of 50 to 55 ° C but the process proceeds at all speeds and at significantly lower temperatures (even around 10 ° C), which makes leaching leaching possible in a significant part of the year in moderate and even cooler climates.

Production solutions containing dissolved precious metals are processed most effectively by metal zinc cementation, resulting in a corresponding concentrate (gold, silver or golden silver depending on the composition of the ore). Concentrates can be processed by conventional hydro and pyrometallurgical processes to produce pure gold and / or silver.

After the cementation the solutions are regenerated to bring their composition to the desired values of the individual components and are recycled in the process scheme for further leaching of the already partially leached ore or leaching new batches of ore. After the leaching is complete, the ore is washed with water, the washes are treated by metal zinc cementation and used to produce a fresh leachate solution and the washed ore is deposited in the waste ponds.

The method according to the invention has the following advantages:

- ensures the process of extraction of precious metals from the high-speed oxidized ores;

- a high degree of extraction of precious metals is achieved by attacking the same mineralization phases of these metals as with conventional hydrometallurgical methods;

- as a complexing agent for dissolved precious metals, together with thiosulphate, an inexpensive and accessible waste product is used;

- the cost of thiosulphate and copper ions are lower than those of chemical leaching without amino acids;

- the dissolved precious metals in the production solutions do not settle spontaneously for an extended period of time;

- the method is harmless to the operating personnel and the environment.

EXAMPLES FOR IMPLEMENTATION OF THE INVENTION

1. Example 1 A sample of gold oxide ore from the Gabrovo deposit is subjected to leaching. The useful components in the ore are gold and silver, whose content is 2.3 w / w and 19.3 w / w respectively. The base minerals of the incoming rock are quartz, and precious metals are mainly accumulated in porous iron and manganese hydroxides, which are mainly located in microcracks of quartz. 7.10% of gold and 27.10% of silver are finely dispersed in sulphide and silicate minerals and can not be extracted by hydrometallurgical and biotechnological methods.

The leaching of the ore is carried out on a column of polyvinyl chloride having a height of 1800 mm and an inner diameter of 315 mm. The column has a false bottom, a receiver for the drained production solutions, and a container for dispensing the leach solution to the ore in the column. The column contains 150 kg of ore - 20 mm. The leaching is carried out in a closed circuit, as the production solution from the receiver enters into a column cementiser with zinc chips to extract the precious precious metals. After the cement, the solution enters a regenerator in which the reagent concentrations and volume are brought to the desired levels, and the thus prepared leach solution is introduced into a dosing vessel for the ore in the column. A leach solution of the following composition is used: thiosulphate (added as ammonium salt) - 25 g / l, cupriones / added as copper sulphate (1 g / l), Microbial hydrolyzate from Caesarean solanacearum / total protein content 36.84% nitrogen - 5.89% - 1 w / 1, pH

8.5 - 9.0 (maintained with ammonia). Norm and dew-rate regime - daily with 120 l solution / Mg ore. Leaching is carried out at a temperature in the range of 16-18 ° C.

Recycled solutions are analyzed daily at the three main points of the flow chart: before entering the ore column, after leaching from the column (before cementation) and after cementation. The following parameters are monitored: solution volume, pH, temperature, content of gold, silver, thiosulphate, amino acids.

The content of dissolved precious metals is determined by plasma and atomic absorption spectroscopy. Upon completion of the leaching, the residual precious metal content of the ore is determined by coupling.

As a result of leaching for 35 days, 82.4% of gold and 62.6% of silver in ore were extracted. With cyanide leaching control, 77.0% of gold and 58.5% of silver were extracted at the same time. A 75.2% gold and 52.1% silver extraction was extracted from the control leaching with thiosulphate solution (25 b / 1) and copper ions (1 b / 1), and in control leaching with a solution of amino acids (5 b) 1 / and KMnO _4/5 β / 1 / - 68.4% gold and 50.5% silver from the same period of time / 35 days /.

The consumption of thiosulphate in leaching is 3.7 kJ / ore ore, and copper - 0.41 sq. / Mg ore, while the cost of these chemical leaching reagents with thiosulphate and copper are respectively

4.4 and 0.53 sq / min ore.

Example 2 A leachate in the manner described in Example 1 is subjected to a sample of gold oxide ore from the Pettelovo deposit. The ore contains 1.2 w / w of gold and 6.2 w / w of silver. The main mineral is quartz, and precious metals are mainly contained in iron hydroxides. Phase analysis of the ore indicates that 10,80% of gold and 21,50% of silver are finely dispersed in sulphide and silicate minerals.

For 35 days, 77.4% of the gold and 66.4% of the silver from the ore were extracted. In control uzlugvane Amino acid solution / 5 β / 1 / and KMnO _4/5 β / 1 / are extracted 64.4% of gold, and 55.9% of the silver. In the controlled leaching with thiosulphate solution (25 b / 1) and copper ions (1 b / 1), 71.0% of gold and 56.1% of silver were extracted, the thiosulphate consumption being higher / 4.8 kb / Me for the control and 4.1 kb / Me for the experiment).

Example 3 Ore from the Gaberovo field (see Example 1) was leached into a mechanically stirred reactor. The ore has a particle size of 0.1 mm. The reactor contains 500 ml of leach solution with composition: thiosulfate / ammonium (100 g / l), cupriones (copper sulphate) - 3 g / l, microbial hydrolyzate 3 g / l, pH 8.5-9.0 (maintained with ammonia) and 150 bp. Leaching is carried out at a pulp agitation rate of 300 vol. / min at 27 ° C. For 12 b, 90.1% of gold and 70.7% of silver are extracted from the ore. 87.8% of gold and 68.6% of silver are extracted from cyanide leaching, and 84.8% of gold and 67.1% of silver in controlled leaching with thiosulphate and cuprions.

Example 4 In 1993 near the flour factory "Elshitsa" a pilot installation for leaching of precious metals from gold-bearing ores from the Pettelovo deposit was built. On a concrete site is loose chalda in the form of a truncated pyramid. The chalda contains 415 liters of ore with a gold content of 2.2 w / w and silver of 10.5 w / w. The ore is 90 to 30 mm thick.

Leaching of the ore begins with alkalizing its acidifying components (sulphate, pyrite and other sulphides) by lime solutions. Upon reaching the alkaline pH (pH 8-9), precious metal leaching begins with solutions containing ammonium thiosulphate, protein hydrolyzate of microbial origin and copper ions. The production solutions are treated by metal zinc cementation. In 32 days, 36.39% of gold and 27.50% of silver in the ore were recovered.

Claims (2)

Claims 1. A method for the extraction of noble metals from oxide ores, in which the ores are leached with an aqueous solution of thiosulphate and copper ions in halves or reactors and the production solutions are processed by known methods of cementation, sorption, ion exchange, to recover the dissolved nobles metals in concentrate form 10, characterized in that the leaching solution further comprises amino acids of microbial origin, which are obtained after hydrolysis of microbial biomass at the following individual concentrations. 15 components in β / 1: thiosulphate - from 10 to 200, cupriions - from 0.2 to 5, amino acids of microbial origin - from 0.5 to 5, the pH of the solution is slightly alkaline, in the range from 8 to 9. A method according to claim 1, characterized in that a hydrolyzate from the biomass of SassBagotusez 1asbz is used as a source of amino acids.