Prospects for using glauconite-containing tails after enrichment of phosphorites to reduce nickel mobility in soils

The phosphorite enrichment tailings (ET) of the Vyatka-Kama deposit are a valuable agrochemical raw material containing phosphorus, potassium, sulfur and a complex of deficient microelements. The presence of an effective natural sorbent glauconite (up to 70 %), lime and phosphate materials in ET plant makes it possible to use them as ameliorants for the rehabilitation of soils contaminated with heavy metals, in particular nickel. As a result of laboratory studies, it was found that the introduction of natural and ground ET, as well as fertilizers based on them in a dosage of 0.25 g per kg of soil leads to a decrease in the mobility of nickel in average by 35 %. The decrease in the mobility of Ni may be due to the adsorption of this element on glauconite. The possibility of the formation of poorly soluble nickel phosphates cannot be ruled out either. The introduction of ET leads not only to a decrease in the mobility of Ni, but also to the enrichment of the soil with phosphorus, potassium, sulfur, and nitrogen. The accumulation of bound forms of nitrogen in the soil is due to the activation of microbiological processes of nitrogen fixation. The agrochemically valuable composition is an important advantage of ET in comparison with lime materials used for binding Ni. Enrichment tailings are distinguished by environmental safety, low cost and availability. The use of ET as natural soil ameliorants will allow us to develop the technology of complex processing of extracted phosphate raw materials and significantly reduce the amount of waste generated during the extraction and enrichment of phosphate raw materials.