ИСТИНА

During hydrometallurgy oxidative processing of non-ferrous metal ores, a red by-product is formed composed mostly of hematite, which is a ferric oxide - a natural red pigment.  In contrast to natural mineral, the red tailings contain hematite in ultradisperse state (<10 um), which makes it mobile upon release into the environments. Same color and contamination type has acid mine drainage. To prevent a spread of pollution with hematite and neutralize its reddish color, we proposed to use natural black color pigment - humic substances (HS), which mask hematite color in soils, as their mineral-adhesive compositions with aminoorganosiloxanes (AOS). The goal of this work was to develop humics-based compositions capable of reducing migration of hematite in the environment and neutralise its red color.  We used interpolyelectrolyte complexes (IPEC) based on coal humate and four different AOS. Previously, we have shown that IPEC of HS and 3-aminopropylethoxysilane (APTES) could restore soil structure by enhancing formation of waterproof soil aggregates [1]. The HS-AOS complexes of different stoichiometry were prepared by adding AOS into the concentrated solution of sodium humate (20% mass). The red tailings contaminated with hematite contained 36% Fe and had a moisture content of 29%. The HS-AOS compositions were applied onto the surface of tailings and thoroughly mixed. Screening of their efficiency was conducted with a use of express test on water stability of the produced aggregate. The best composition was HS-APTES. It was tested also with a use of wet sieving technique. Application of HS-APTES to the red tailings showed an increase in water-resistant aggregates with a diameter >0.2 mm from 13 to 35%. With an increase in the APTES:HS ratio in the complex, the proportion of aggregates <0.2 mm decreased, reaching a minimum at a ratio of 1.5:1; a further increase in the APTES dose did not lead to significant improvements in soil characteristics. An increase in the average size of tailing aggregates indicated the binding effect of IPEC on hematite and clay particles, which reduced its mobility and prevents the spread of pollution. In addition, the treated tailings got dark brown color. Acknowledgment. This research was partially supported under the State Budgetary Task 122040600057-3. Literature 1. Kulikova, N. A., et al. Modified humic substances as soil conditioners: laboratory and field trials. Agronomy-Basel 11, 1 (2021), 150. DOI 10.3390/agronomy11010150