Vestnik MGTU (Mar 2021)
Separate deposition of metals from highly concentrated solutions with granulated magnesia-silicate reagent
Abstract
Multi-stage deposition of metals from a sulfate solution with a high concentration of iron, aluminum, copper, zinc, and nickel has been studied. The concentrations of the components correspond to the composition of the sub-basement waters of the Gaisky GOK. Granular magnesia-silicate reagent based on serpentinite (Khalilovsk magnesite deposit, the Orenburg region, Russia) has been used as an alkaline agent. The magnesia-silicate reagent's ability to reduce the acidity of solutions is due to the presence of products of destruction of the original serpentine mineral, mainly magnesium oxide. The results of the solutions multi-stage purification from metals simulation have been presented. It has been found that the reagent did not wholly exhaust its activity during a single contact with the solution. Therefore, the possibility of its repeated use for the 2nd and 3rd time has been studied. As the solution is neutralized according to the known pH range of the beginning and complete deposition of metal compounds, first iron, and then aluminum are deposited. For copper and nickel, the effect of co-precipitation is observed until the pH of precipitation of poorly soluble compounds is reached. Iron is the main component of precipitations at the 1st, 2nd, and 3rd stages, which corresponds to pH = 2.4–3.7. At the 4th stage (pH = 4.0), the precipitations consisted mainly of aluminum compounds. The copper and nickel content in precipitations increase due to decreased concentration of major components (aluminum and iron) and a pH increase. The deposition of zinc from the solution occurs not to the precipitations, but on the granules surfaces. Precipitations enriched in aluminum and iron have been obtained. Sorption and co-precipitation processes have been observed for copper, zinc, and nickel, which prevents individual precipitation by these metals. Thermally activated serpentine minerals can be considered a promising alkaline reagent for technogenic solutions neutralization and purification.
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