X Международная студенческая научная конференция Студенческий научный форум - 2018

A large amount of man-made waste creates technical and environmental problems of their removal and neutralization, leading to significant environmental stresses as a result of pollutant emissions.

Handling of man-made wastes includes the following stages of the movement: formation, collection, temporary storage, transportation, processing, neutralization and disposal of unutilized residues. Each stage of waste management has a positive or negative impact on the entire waste management system, depending on the effectiveness of the decisions made. Management of man-made wastes is basically reduced to the organization of their collection, transportation and disposal. The resulting man-made wastes are stored in landfills, many of which do not meet the requirements of environmental and health safety. This practice of waste disposal leads to long-term pollution of the environment, comparable in degree of danger with radiation pollution. Since wastes are potential secondary material resources, the current system of disposal of man-made waste leads to a permanent loss of valuable secondary material resources, energy and land resources. The environment is exposed to the negative impact of stored waste for decades. Over the years, the intensity of this impact is not always reduced, but can have sharp periodic increases as a result of changes in geological, hydrological and hydrogeological conditions. It should be borne in mind that over time the probability of violations in the engineering protection system increases, which is not designed for operation for a decade, and, therefore, can not guarantee environmental safety of such facilities in the long-term aspect.

Effective application of pyrolusite as an oxidizer is possible to solve various chemical, technological and environmental problems. Thus, for example, it is noted that pyrolusite MnO2 can be used as an oxidizing agent for gold (and silver) recovery in hydrochloric or sulfuric solutions containing chloride ions [1,2].

MnO₂ + 4H⁺ = Mn⁴⁺ + 2H₂O

Mn⁴⁺ + 2Cl^- = Mn²⁺ + Cl₂

2Au +8Сl^- + 3Mn⁴⁺ = 2AuCl₄^- + 3Mn²⁺

2Au +3Сl₂ + 2Cl^- = 2AuCl₄^-

2Au +8Сl^- + 3MnO₂ + 12H = 2AuCl₄^- + 3Mn²⁺ + 6H₂O

Along with this, an effective method of complex hydrometallurgical processing of matte lead plants was developed by sulfuric acid leaching with the use of manganese dioxide as an oxidizer.

To clarify the role of individual components of the system in the establishment of redox potentials, let us consider, for example, the variation of E ° in the system UO2-MnO2 Fe (II) -H2SO4 with a gradual complication of its composition. As follows from these data, the highest potential is observed when the system contains only manganese dioxide. At the same time, the degree of oxidation of uranium dioxide under these conditions is low. Taking into account that manganese dioxide is practically insoluble in dilute solutions of sulfuric acid at 40 ° C [3,4], it becomes clear how small amounts of this oxidant in the solution or on the surface of the electrode are sufficient to establish a high value of E °.

From our point of view, the most suitable method for opening rhenium-containing lead dusts is the direct hydrometallurgy method, which is more economical. The use of oxidants can significantly increase the extraction of metals in the solution. However, the use of nitric acid, hydrogen peroxide, potassium permanganate did not bring success either because of the high cost, or because of the additional impurities introduced into the solution, which complicate its further processing. Therefore, there was a need to find an inexpensive, affordable and sufficiently effective oxidizer. Such oxidants can be manganese compounds.

The use of various natural manganese-containing materials as an oxidizer for extraction of rare and non-ferrous metals from lead-containing industrial products was considered in [5].

Attempts to use manganese ore to open lead dusts at the Ust-Kamenogorsk lead-zinc plant did not go beyond laboratory tests [6]. The following leaching regime is proposed: G: T = 2: 1, temperature - 75-85 ° C, initial concentration of sulfuric acid - 200-220 g / dm3, amount of manganese ore - 3.4 g per 1% of sulphide sulfur, leaching time - 2 hours. The degree of extraction into the solution was,%: zinc 76-82, cadmium 66-89.5, thallium 60-62, arsenic 69-78, no data on rhenium.

The authors of Ref. [7] used manganese concentrate with a content of 30-40 mass% manganese as an oxidizing agent to extract rhenium from sulfuric acid slimes of the Zhezkazgan copper smelter. The technological parameters of leaching were studied: temperature, F: T, time, oxidizer consumption. On the basis of experimental data, the optimal regime was chosen: G: T = 5: 1, temperature - 90 ° C, initial concentration of sulfuric acid - 200-250 g / dm3, leaching period - 2 hours, manganese ore consumption - 10% of the sludge weight. The extraction of rhenium in the solution was 70-72%. Industrial tests showed a lower recovery of rhenium (50%) in solution as compared to laboratory tests. The authors explain this position by a lower leaching temperature (70 ° C). Along with rhenium, 51% cadmium and 63 zinc are extracted into the solution. The solutions after the leaching were directed to extraction of rhenium by extraction. There are no proposals on the extraction of cadmium and zinc.

There are data on the use of manganese-containing material for the leaching of lead-zinc cakes [8]. The authors of the article studied and proposed the following leaching regime: temperature - 70-80 ° С, Ж: Т = 5: 1, time - 8 hours. A significant influence on the extraction of metals in the solution, as well as on the quality of the zinc sulfate produced, is provided by the consumption of the oxidizer. At an oxidizer consumption of 0.8-1.6% (based on the weight of the leachate), the recovery into the solution was,%: zinc 67.5, cadmium 77.1, indium 68.0. Increasing the oxidizer consumption from 5 to 20% significantly increases the recovery of rare metals, as the authors claim (unfortunately, numerical data are not available), but decreases the quality of zinc sulfate. The reason for this is an unacceptably high level of impurities, additionally introduced with the oxidizer into the main process solution. It is known that the purification of solutions from manganese is complicated by the fact that manganese, along with potassium, sodium and magnesium, belongs to the number of impurities practically eliminated from the zinc solution.

Thus, the analysis of scientific, technical and patent literature devoted to the extraction of rare and non-ferrous metals from industrial products of lead production using manganese compounds as oxidants has revealed a positive effect of these oxidants on the degree of transfer to solution of some metals, but the information on this issue is limited and disaggregated , there are no judgments and points of view of the processes that are taking place. The conducted researches can be characterized as search.

Bibliography

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2 Heap leaching of precious metals / Ed. M.I. Fazlullina. - M.: Publishing house of the Academy of Mining Sciences, 2001. - 647 pp.].

3 Grachev V. V., Samoylenko V. M. // Non-ferrous metals. 1982. № 5. P. 34-35.

4 Agladze R.K., Jincharadze M.D. // Journal. prikl. chemistry. 1978. P. 51, No. 8. P. 1886 -1887.

5 Cheremisina O.V. Extraction of non-ferrous and rare metals from metallurgical waste and non-traditional sources of raw materials using crystallization and sorption processes. Diss. on s.is.uch.step. Doctor of Technical Sciences. St. Petersburg, 2010

6 Plaskin I.N. Ion exchange and extraction in ore processing processes / Ion-exchange and extraction methods in chemical-processing processes. Moscow: Nauka, 1965. P. 3-13.

7 V.V. Zyk, Zh. N. Galieva. Obtaining REE oxides from solutions of phosphogypsum leaching. // Весцi Нацяянальнай акадэмii навук Беларусi Сер. хiм. an ape. Belarus. 2001. №1. Pp. 12-14.

8 Ponomareva E.I. et al. Self-sustained agglomeration of rhenium-containing scoria dusts // Chemistry and Technology of Rare Metals. Sb.nauch.trudov IMiO AN of the Kazakh SSR, Almaty, 1981, 3-16 p.

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