Application of polystyrene sulfonates for the depression of magnesium-containing silicates in copper-nickel ore flotation

It is very urgent to increase the efficiency of depressing magnesium-containing silicates (MS) in the course of the flotation of copper-nickel ores to reduce the content of magnesium in the concentrate, which causes a significant increase in energy consumption in pyrometallurgical processing of the concentrate. The use of polymer reagents containing sulfo groups seems to be a promising area of research. However, only lignosulfonates have been studied so far in this field. The question of the effectiveness of the depressing effect of other polymer sulfonates including polystyrene sulfonates (PSS), and their comparison with polysaccharides used in industrial conditions remains unclear. The purpose of this work is to study the depressing effect of PSS on the performance of bulk flotation of copper-nickel ores. Research objectives: to experimentally compare the effectiveness of the depressing effect of PSS and a reagent from the polysaccharide class on MS; to determine the modes of PSS use to reduce the magnesium content in the concentrate without significantly reducing the recovery of copper and nickel into the bulk concentrate; to establish the effect of molecular weight and the method of obtaining PSS samples on the effectiveness of their depressing effect. Laboratory experimental studies were carried out on the bulk flotation of copper-nickel ores from the Kola Peninsula, containing 15.7% of magnesium, 0.44% of nickel and 0.25% of copper. The effect of the following polymer anionic reagents on the flotation was studied: PSSs with molecular weight ranging from 89,000 to 208,000 g/mol; polyanionic cellulose (PAC-N) was used for comparison. To increase the effectiveness of these reagents, magnesium chloride was previously added. It was found that the lowest magnesium content in the concentrate of 14.7% was achieved using a composition of magnesium chloride and PSS against 16.7% without the depressants. It was shown that PSS provides a higher recovery of copper (by 7%) and nickel (by 8%) into the concentrate than when using PAC-N, since PSS, unlike polysaccharides, does not form chelate complexes with these metals. It was also shown that for PSS samples, the molecular weight within these limits has virtually no effect on the studied ore flotation performance. New scientific knowledge has been obtained about the effect of the consumption and properties of PSS on the flotation performance. It has been shown that the practical use of this class of reagents is advisable for the flotation of copper-nickel ores with a high magnesium content in cases where it is necessary to achieve the maximum possible decreasing the content of this element in the concentrate without significantly reducing the recovery of copper and nickel.