Investigation of the Possibility of Immobilization of Mobile Forms of Arsenic in Technogenic Soils
- 1 — Ph.D. Associate Professor Irkutsk National Research Technical University
- 2 — Ph.D., Dr.Sci. Professor Irkutsk National Research Technical University
- 3 — Ph.D., Dr.Sci. Professor Irkutsk National Research Technical University
Abstract
Levels of contamination of three mining industrial zones in Irkutsk Oblast and Zabaykalsky Krai were revealed by means of geoecological and geochemical monitoring. Bulk contents and mobile forms of As in soils, stubs, bricks, and dumps of the mining and processing industry were defined. This allowed revealing features of chemical composition of technogenic substrates for the purpose of a choice of a way of their neutralization. The possibility of chemical immobilization of mobile ionic forms of As in natural and man-made objects by treatment with alkaline reagents was studied. X-ray diffraction (XRD) analysis revealed pharmacolite CaHAsO4·2H2O, calcium arsenate Ca3(AsO4)2, and segnititePb(Fe3+)3AsO4(AsO3OH)(OH)6 that are formed in the obtained solid insoluble precipitates. Formation of new solid insoluble compounds indicates the chemical binding (immobilization) of arsenic-containing compounds and the irreversibility of the process. This allows us to offer an effective way of fixing toxic agents to reduce migration in the environment by stabilizing immobilized forms. Experiments with the use of lignin sludge ash (accumulated waste of the closed Baikal pulp and paper mill) for the neutralization of arsenic-containing waste of mining and metallurgical industries were carried out. Application of modified coal sorbing agents for the sorption of residual mobile forms of As (after treating with an alkaline reagent) allows achieving a decrease in its concentrations to the TLV standard for a hazardous substance. NoritRO 3520 is the most effective sorbing agent. The results are of high applied importance for the implementation of the method of chemical immobilization of mobile ion forms of As in technogenesiszones.