The sorption of Mo(VI) ions on natural sorbents (zeolite tuffs and clinker) is investigated. It is estimated that zeolite tuffs sorb polymer forms of Mo(VI) ions in acidic media, while the monomer form of molybdate ion is sorbed in basic media. It is concluded that the rate of sorption of molybdenum(VI) ions on zeolite tuffs is regulated by an intradiffusional mechanism. Values of the activation energy indicate that the adsorption of molybdenum(VI) ions on zeolite tuffs is governed by a physical mechanism. The excretion of crystalline phase (probably calcium molybdate) on surfaces of zeolite tuff is estimated via scanning electron microscopy.

Lake Gusinoe is the second largest freshwater lake in Transbaikalia. Lakes serve as a source for drinking water, irrigation, and as a water source for the electricity, aquatic production, and tourism industry. Currently variations of content nutrients and organic matter differ in different areas of the lake. The content of total nitrogen, phosphorus, organic matter, and dissolved oxygen are distinguished more than 1.2–2.0 times. In accordance with the behavior of elements in the water, three groups of elements can be distinguished. The first group of elements, including Li, Ga, Ge, As, Rb, Sr, Mo, Cd, W, and U, were directly correlated with variations of major elements. The first group of elements showed decreasing concentrations with an increasing amount of total dissolved salt (TDS). The second group of elements, including Fe, Y, Nb, Th, and REE, were correlated oppositely with variations of TDS. The behavior of the third group of elements, including Mn, Zn, Ni, Cu, and Pb, decoupled with TDS. The value of the Eu anomaly was positively correlated with TDS. The water of Lake Gusinoe was extremely enriched by W, Mo, V, U, Li, Sr, and Ga; moderately by Ni, Cu, Ge, As, Rb, Cd, and Pb; and minimally by Al, Cr, Mn, Fe, Co, Zn, Y, Th, and REE.

The possibility of concentrating non-ferrous metals (NM) – Zn, Cu, Cd, Co, Ni – and rare earth metals (REM) from liquid waste from the processing of tungsten ores using limestone has been studied. For the work, two sand samples were selected from different points of the tailing storage, differing in the content of NM and REM. Liquid waste is obtained by filtering distilled water through sand according to a developed scheme. The composition of resulting filtrates depends on the composition of original sand and the filtration water volume. The maximum content of NM and REM reached in the first portions (3 l) of the filtrate, mg/l: 1420 Zn; 320 Cu; 21 Cd; 9.5 Co; 7.4 Ce; 5.3 Ni; 2.9 La; 2.6 Nd; 2.6 Y; 0.75 Pr; 0.43 Sm; 0.43 Dy; 0.36 Gd; 0.26 Er; 0.095 Eu; 0.09 Ho; 0.068 Tb; 0.039 Tm; 0.25 Yb; 0.02 Lu. It has been established that while washing sands with distilled water, the filtrate becomes less concentrated. Based on the results of measuring pH and determining the content of chemical elements, it was concluded that the pore waters of sands contain a limited amount of dissolved substances, which are washed out of them during the filtration with distilled water. The facility for concentrating NM and REM from acidic filtrates was designed in the form of a horizontal chute with compartments filled with limestone. The filtrate entered the chute through textile and paper filters to separate suspended particles. At certain intervals, water and limestone samples were taken from the compartments for chemical analysis. The process of concentrating NM and REM with limestone is accompanied by the neutralization of liquid waste from pH 3.35 to 6.49 and from 4.85 to 6.32. The maximum concentration of zinc recorded in waste limestone reaches 80 g/t, copper — 75 g/t, cadmium — 11 g/t, yttrium — 12.3 g/t. The total concentration of all rare earth metals in limestone reaches 32 g/t. The formation of smithsonite, gypsum, and fluorite on the surface of waste limestone was revealed.The study was carried out within the framework of the state assignment of the Russian Academy of Sciences Geological Institute of SB RAS under project No. АААА-А21-121011890033-1.

Environmental pollution with acid mine waters remains a challenge for the sustainable development of the mining industry. The article describes the experimental treatment of mine drain water at the Dzhida tungsten–molybdenum deposit in the Republic of Buryatia to remove metal ions and suspended solids using local natural materials. The natural materials were selected to be rocks from the adjacent deposits, namely, montmorillonite clay, zeolite-containing tuff, limestone, volcanic slag, serpentine, calcite, quartzite, coal and coal ash. It is concluded that the neutralizing ability of these materials is the determining factor in the removal of metal ions by means of precipitation of hydroxides. Lead ions are removed almost totally, while tungsten ions are removed worse. Further, it is found that strength characteristics of mordenite-containing tuff, volcanic slag, serpentine, calcite and quartzite enable using them as filtering materials. Since removal of suspensions from mine water in columns was more efficient with zeolite-containing tuff and volcanic slag, the latter were included in the experiments to select the optimal fractions and water flow rate. In the dynamic mode, zeolite-containing tuff demonstrated the higher retention capacity of metal ions of zinc, tungsten, cadmium and copper. To assess saturation of the filtrate with the elements from the matrix of zeolite-containing tuff and volcanic slag after contact with distilled water, the chemical analysis of the aqueous extract was carried out using the ICP-MS method. It was revealed that Na ions were leached in the greatest amount, while the leached amount of Mg, Al, K, Ca, Ti, Fe, B, Mn, P, Rb, Zr, Li, V, Cu, Zn, Ga, Se, Nb, Mo, Cs , Ba, Sn, W, Pb, Be, Sc, Co, Ni, Ge, As, Cd, Sb, Re, Tl, Bi, Th and U was smaller. In the contact of zeolite-containing tuff with 20 % water solutions of chlorhydric acid as against distilled water and alkaline solutions, removal of aluminum and silicon ions of zeolite framework was the least. The work was carried out within the framework of the state task of the Geological Institute of Siberian Branch of Russian Academy of Sciences (project АААА-А21-121011890033-1).