RU2623948C1 - Method of integrated treatment of pyrite cinders - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used to produce pure iron compounds, non-ferrous and noble metal concentrates from pyrite cinders that are waste products of sulfuric acid production. Leaching of iron and non-ferrous metals is carried out in a counterflow mode in two stages using a solution of hydrochloric acid with a concentration of 150-240 g/l, at a temperature ≥of 60°C. The undissolved residue is separated from the solution, washed off excess acidity and sent to the recovery of noble metals. Hydrochloric acid solutions after leaching are treated with chlorine gas, the pH value is adjusted to pH=0.5, then metal sulphides or hydrogen sulphide are dosed in them, arsenic precipitates are recovered from the solutions. After separation of the solution from the precipitate, thermal decomposition of ferric chloride is carried out to produce pure iron oxide. The evolved hydrogen chloride is trapped by solutions of washing the precipitation after cinder leaching. The obtained hydrochloric acid is returned to the stage of hydrochloric acid leaching of new portions of the cinder.

EFFECT: increasing the recovery of iron, non-ferrous and noble metals.

5 cl, 5 tbl, 3 ex

Description

The invention relates to the field of hydrometallurgy and can be used to obtain pure compounds of iron, concentrates of non-ferrous and noble metals from pyrite cinders, which are waste products of sulfuric acid production.

A known method of extracting zinc and copper from a pyrite cinder [USSR Author's Certificate No. 1157101, C22B 15/00, publ. 1985.05.23] by treating it with an aqueous ammonia solution in two stages with a ratio of solid and liquid phases (T: G) = 1: (15-20) in the first stage with a solution containing 3-7% ammonia and 0.02-0.05 % ammonium sulfide, and in the second stage - a solution containing 15-20% ammonia. Zinc oxide is isolated from the first filtrate by distillation of ammonia, then the precipitate is separated on the filter. Copper oxide is isolated from the second filtrate by distilling off ammonia, which is also separated on the filter.

The disadvantages of this method are the lack of operations for the extraction of iron and precious metals, as well as the contamination of the resulting products with arsenic.

A known method for the extraction of non-ferrous and precious metals, mainly copper and gold, from pyrite cinder [RF Patent No. 2 342 446, class. IPC С22В 11/00, С22В 15/00, С22В 3/08, publ. 2008.12.27], including the construction of an anti-filtration base, the formation of a pyrite cinder dump on it, the collection of solutions formed under the influence of atmospheric precipitation during the settling of dumps of solutions containing sulfuric acid and ferric ions, the use of these solutions, after adding sulfuric acid to them to pH = 1.5-1.9, for leaching of non-ferrous metals, precipitation from the resulting productive copper solutions by cementation, aeration of the mother liquors of cementation to a decrease in their copper concentration of less than 100 mg / l, introduction into the mother liquors of cementation of thiocarbamide, leaching of precious metals, mainly gold, at a concentration of thiocarbamide 0.2-0.5 g / l and pH and Eh values determined by the stability region of the gold-containing thiocarbamide complex and the minimum value necessary to keep gold in solution, isolation from obtained productive gold solutions by cementation on precipitation from the stage of copper deposition.

The disadvantages of this method are a significant increase in the duration of the process due to the use of precipitation for the production of acid basement waters, as well as the absence of operations for extracting iron and obtaining iron-containing products.

A known method of deep processing of pyrite cinders [RF Patent No. 2397260, IPC C22B, publ. 2010.03.10], including the leaching of non-ferrous metals by a bacterial complex consisting of four types of acidophilic thionic bacteria in the active growth phase with the cultivation of microorganisms in solution and their accumulation during the creation of a slightly acidic environment and the active oxidation of pyrite with the conversion of iron, copper, zinc into the liquid phase, arsenic, lead and antimony. Canned leaching of the cinder is carried out at T: W = 1: 5, the oxidation rate of iron is 24-26 g / l per day. After leaching of non-ferrous metals, gold and silver are recovered.

The disadvantages of this method are the long duration of bacterial leaching and the complexity of the process of culturing acidophilic thionic bacteria.

Closest to the proposed invention in terms of technical nature and the achieved effect is the method of complex processing of pyrite cinders selected for the prototype [USSR Author's Certificate No. 1,669,193, class. MKI C22B 3/44, C22B 15/00, C22B 19/00, publ. 2000.07.20], including four-stage leaching of non-ferrous metals with water and a solution of sulfuric acid and leaching of precious metals with hydrochloric acid solutions of thiocarbamide. At the same time, sulfuric acid is dosed to a pH of 1.9-2.0 in an aqueous solution that has gone through three stages of cinder leaching at a ratio of T: W = 1: 1.6, blister copper is isolated from solutions after leaching by adding iron scrap to achieve values of Eh (0 - (- 80 mV), then after separation of the solution from the precipitate, the Eh value is raised to 600-700 mV and the soda is dosed until pH = 6.0, the precipitate formed in this case is separated from the solution and subjected to heat treatment to obtain iron oxide pigment , and from the clarified solution by precipitation with soda at at a temperature of 60 ° C and a pH value of 7.8, zinc carbonate is isolated with its subsequent conversion to oxide, the cinder after separation from the sulfuric acid leaching solution is sent to the precious metal extraction operation with a hydrochloric acid solution of thiocarbamide.

The disadvantages of this method are the low extraction of iron and precious metals from the cinder, as well as the contamination of the obtained iron oxide pigments with impurities of non-ferrous metals and arsenic.

The main technical result of the proposed method is to increase the extraction of iron, non-ferrous and noble metals. In addition, the proposed method allows to obtain pure iron compounds, from which high quality iron oxide pigments can be obtained, which can replace currently purchased abroad.

The specified technical result is achieved in that the leaching of iron and non-ferrous metals from the pyrite cinder is carried out in countercurrent mode in 2 stages, with solutions of hydrochloric acid with a concentration of 150-240 g / l, at a temperature of ≥60 ° C, after separation of the insoluble residue it is washed from excess acidity and sent to the extraction of precious metals. Hydrochloric leach solutions are treated with gaseous chlorine, the pH value is adjusted to pH = 0.5, then metal sulfides or hydrogen sulfide are dosed to precipitate arsenic. After the solution is separated from the precipitate, iron chloride is thermally hydrolyzed to obtain pure iron oxide, the resulting hydrogen chloride is captured by precipitate washing solutions after cinder leaching, the resulting hydrochloric acid is returned to the hydrochloric acid leaching stage of iron and non-ferrous metals from fresh coke portions. The extraction of precious metals from the precipitate after leaching of iron and non-ferrous metals is carried out by known methods, the precipitate after the extraction of precious metals is an additional type of useful product, since it contains mainly quartz sand.

To substantiate the essence of the proposed method and identify its advantages, a large amount of experimental work was carried out to determine the optimal parameters of the process. Some of the results obtained during experimental work are presented in the examples.

Example 1

The experiments were carried out on a pyrite cinder, selected from a bowl of a cinder deposit of sulfuric acid production. The chemical composition of the pyrite cinder sample is presented in table. one.

The initial pyrite cinder and an acid solution of a given concentration pre-heated in a water bath were mixed with continuous mechanical stirring for a predetermined time and filtered on a vacuum filter. The solution and washed cake were sent for analysis. The cake was washed with acidified hydrochloric acid to pH = 1 with hot water, then with hot water alone.

In the first series of experiments, hydrochloric acid leaching was carried out at a temperature of 80 ° C, in one stage, the concentration of hydrochloric acid in the initial solution was 200 g / dm ^3. The experimental results are given in table. 2.

As can be seen from the data presented, when leaching with hydrochloric acid with a concentration of 200 g / dm ^{3, the} extraction of iron in the solution was reached at the level of 75%, which is significantly higher compared to the prototype method in which the extraction of iron into the solution was 1.04%.

An even greater degree of iron recovery is achieved by leaching the cinder in 2 stages, in countercurrent. The second series of experiments was carried out according to the following procedure.

Three sample cinders, weighing 150 g each, were treated with hydrochloric acid solutions for two hours at a temperature of 60 ° C, then the cinder was separated from the solution and sent to the second stage of leaching with a fresh acid solution at a temperature of 80 ° C. After 2 leaching stages, the cinder was washed and the content of the target components was determined in it, and the degree of their extraction was determined by the results of the analyzes. The solution from the second leaching stage was sent to leach a new sample of the initial cinder, after leaching of which, for two hours, the concentration of the target components was determined in the productive solution. The results of experiments with the sequential leaching of four webs of cinder (after reaching equilibrium concentrations of the target components in the solution and the residual content in the precipitate after leaching) are given in table. 3.

Example 2

A productive solution was prepared by two-stage leaching of the initial cinder with hydrochloric acid solutions at W: T = 6: 1. Three samples of a solution of 0.5 l each were poured into glass cylinders. MgO was added to the first cylinder until pH = 0.5 was reached, then 1 g of Na ₂ S (in the form of a solution with a concentration of Na ₂ S = 77 g / dm ² ) was stirred for 15 minutes, after which the solution was separated from the precipitate formed and determined in it the content of the target components. The solution in the second cylinder was treated with chlorine gas for 15 minutes, then MgO was added until pH = 0.5, 1 g of Na ₂ S was added (in the form of a solution with a concentration of Na ₂ S = 77 g / dm ³ ), stirred for 15 minutes, after which the solution was separated from the precipitate formed and the content of the target components was determined in it. The solution in the third cylinder was treated with chlorine gas for 15 minutes, then MgO was added until pH = 0.5, 1.2 g of FeS was added, stirred for 15 minutes, after which the solution was separated from the precipitate formed and the content of the target components was determined in it . The experimental results are given in table. four.

As can be seen from the table. 4 data, the proposed method provides for obtaining residual concentrations of arsenic is significantly lower compared with the prototype method.

Example 3

Gold and silver were leached from thiocarbamide solutions acidified with sulfuric acid from an insoluble precipitate washed from hydrochloric acid. Agitation leaching was carried out for 6 hours, at a temperature of 20-25 ° C and a ratio of W: T = 3: 1. For comparison, under the same conditions, the initial cinder was leached, previously washed with water and weak sulfuric acid solutions (in the prototype method mode). The experimental results are given in table. 5.

As can be seen from the data presented, the recovery of gold and silver from precipitation after leaching of the calcine with hydrochloric acid is significantly higher than from the calcine washed with water and a weak solution of sulfuric acid (as in the prototype method). This is due to two main factors: an increase in the content of noble metals in the precipitate after the dissolution of iron, as well as the release of quartz particles containing gold and silver from the cakes formed during the calcination of sulfur pyrite in the process of producing sulfuric acid.

From the above examples it is seen that the inventive method of complex processing of cinder provides, in comparison with the prototype method, an increase in the extraction of iron, non-ferrous and noble metals, and also allows you to get pure compounds of iron.

Claims (5)

1. A method of complex processing of pyrite cinders, including leaching of iron and non-ferrous metals with a solution of mineral acid, separation from a solution of non-ferrous metals, obtaining iron compounds and extraction of precious metals from a leached cinder, characterized in that the leaching of iron and non-ferrous metals is carried out with a concentration of hydrochloric acid 150-240 g / l, at a temperature of ≥60 ° C, undissolved precipitate is separated from the solution, washed from acidity and sent to the recovery of noble metals, in solyanokis Warm leaching solutions dose metal sulfides or hydrogen sulfide, precipitate arsenic precipitates from the solution, and then the remaining iron chloride solution is subjected to thermohydrolysis, while the resulting hydrogen chloride is trapped in aqueous solutions to obtain hydrochloric acid, which is returned to hydrochloric acid leaching, and the resulting pure iron oxide is directed to obtain iron oxide pigments. 2. The method according to p. 1, characterized in that the hydrochloric leaching of the cinder is carried out in countercurrent mode in two stages. 3. The method according to p. 1, characterized in that before the dosage of metal sulfides or hydrogen sulfide, the hydrochloric leach solutions are treated with chlorine gas and the pH value is adjusted to pH = 0.5. 4. The method according to p. 1 or 2, characterized in that before the operation of thermohydrolysis, the solution of iron chloride is evaporated to a concentration of 200-600 g / L. 5. The method according to p. 1, characterized in that as an aqueous solution for trapping hydrogen chloride, water is used to wash the cinder after leaching with hydrochloric acid.