DEVELOPMENT OF A LOW-TEMPERATURE DESILICONIZATION METHOD FORTHE POLYMETALLIC SLAGS WITH A SOLUTION OF AMMONIUM HYDROGEN FLUORIDE

Abstract

This paper considers a method for removingsilicon dioxide from the polymetallic slags of the Nerchinsk silver smelters, which operated from the 17th to the 19th centuries. The main com-ponents are presented both in the oxygen-containing form (iron, silicon, etc.) and in the form of sulfides (lead,zinc). It was found that during the process, silicon passes into solution in the form of ammonium hexafluorosilicate. Iron, aluminum and a number of other components react with NH4HF2, but stay in the solid phase due to their low solubility in the resulting system. After remov-ing silicon, the solid residue is subjected to pyrohydrolysis to obtain a product that can be subjected to magnetic separation to obtain a magnetic iron concentrate and a non-ferrous metal concentrate, which can later be used to extract zinc, lead, silver, etc. Fluorine is removed from the cycle with the pyrohydrolysis product in the form of calcium fluoride. Productive solution is directed to the silicon dioxide production. The final solution of ammonium fluoride is used for ammonium hydrodifluo-ride by means of the water evaporation. In the process of evaporation of the ammonium fluoride solution, the ammonia molecule is split off with the formation of ammonium hydrodifluoride. The whole process of desiliconization is shown in the technological scheme. Main stages of the method demand typical equipment, so it allows us to speak about the applicability of this method in industry for both mineral and artificial raw materials with a high content of silicon dioxide or silicates of various compositions.