Obtaining selenium concentrate from the slime of the sulfuric acid workshop of the Balkhash copper plant and extracting selenium from it into solution

Abstract

The article presents the results of large-scale laboratory tests of obtaining selenium concentrate from the slime of the sulfuric acid workshop (hereinafter: slime) of the Balkhash copper smelting plant and the extraction of selenium from it into solution. This slime, in contrast to similar slime from non-ferrous metallurgy plants, significantly differs in chemical and material compositions, especially in the selenium content (4.6 - 12.5 wt.%). Involving it in the production sphere will increase the production of selenium by more than 20% from that obtained by the plant from copper electrolyte slime. The slime is washed with water to remove sulfuric acid, dried at 105 ° C. Selenium concentrate was obtained by sequential leaching of slime with solutions of sodium carbonate and nitric acid, selenium from the concentrate was leached with solutions of sodium sulfite (atmospheric pressure) and sodium hydroxide (high pressure, autoclave leaching). Slime, concentrate, cakes, precipitates isolated from solutions, and solutions were analyzed using modern devices of a new generation: An Optima-8300 inductively coupled plasma spectrometer, an Axios X-ray fluorescence spectrometer, an Optima 2000 atomic emission spectroscope, a D8 Advance diffractometer, a D8 Advance infrared spectrometer Avatar 370. From the slime containing, wt. %: 51.2 Pb, 12.5 Se, 3.21 Hg and other elements, a selenium concentrate was obtained with the composition, wt. %: 0.41 Pb, 59.16 Se, 15.4 Hg. The technological indicators for obtaining a concentrate are given, %: concentrate yield - 20.74, Pb recovery - 0.81, Se - 98.23, Hg - 99.50. According to XRD and IR spectroscopy, the concentrate contains elemental selenium and mercury selenide from 10 selenium substances contained in the slime (given in the article). The extraction of selenium from the concentrate into the solution was, %: sodium sulfite - 76.84, sodium hydroxide - 89.65. The pulp from opening the concentrate with sodium hydroxide solution was filtered very poorly. The filtrates contained a colloidal suspension, which could not be filtered off either under vacuum or centrifugation. Therefore, to determine the qualitative and material composition of the filtrates, salts were obtained by evaporating a certain and then neutralized volume to dryness. It was found that only elemental selenium is leached from the concentrate by solutions of both reagents, while mercury selenide remains in the cakes. Moreover, over time, elemental selenium partially precipitated again from selenium-containing sodium sulfite solutions; the salts contain only elemental selenium. An explanation is given for the transition of soluble selenium salts to its elemental state. Despite the higher recovery of selenium from the concentrate by leaching in autoclaves, taking into account the equipment, the complexity of its maintenance, filtration of the pulp and the chemical composition of the filtrate, it is preferable to use the method of leaching with sodium sulfite.