Study of the influence of initial contents of arsenic of the Khovu-Aksy dumps on effectiveness of the developed regimes of their dearsenization

Dumps of arsenic-containing wastes from the former Tuvakobalt combine are one of the most dangerous objects of Tuva. The combine’s wastes were accumulated in ponds (dumps) for 20 years of operation of the combine. After its closure, the ponds were drained and are now exposed to the external environment, namely, groundwater, precipitation and wind erosion. The accumulated dumps contain industrial contents of nonferrous metals and about 50 thousand tons of arsenic. Due to natural precipitation, toxic compounds are flushed to the lower layers of dump maps with subsequent ingress into groundwater and the environment. Long-term studies carried out at the Institute of Solid State Chemistry and Mechanochemistry and the Tuvinian Institute for Exploration of Natural Resources of the Siberian Branch of the Russian Academy of Science were devoted to the issue of dearsenization of arsenic dumps of Khovu-Aksy of the «Tuvakobalt» combine with the aim of processing them and obtaining the secondary raw materials for the production of materials on their basis that can be used as recyclables in the national economy such as cake — as a flux in the production of ceramic and arsenic sulphide in the production of antiseptics in the processing of wood or biocide for antifouling coatings of hulls of ships and hydrotechnical structures. Studies carried out using initial samples of dumps sludge taken from different burial sites and differing in the content of arsenic (1.88 and 4.21 %) showed the possibility of effective dearsenization of slurry materials on the tested technological regimes of the process, regardless of the concentration of arsenic in them, with the formation of cake (with a content of As ≤ 0.3 %) and arsenic sulfide (IV degree of toxicity).