Copper and zinc extraction from underspoil waters using sulfur solution in sodium hydroxide

Abstract

During the passage of atmospheric precipitates through the porous dump body, the products of oxidation of sulfide minerals are dissolved. As a result, underspoil waters with low pH values and a significant amount of dissolved metals are formed. For the most part, all types of the sewage produced by mining and processing enterprises (underspoil, colliery, pit, drainage) are combined before treatment, which leads to the formation of a common water yield with complex chemical composition. According to the existing practice, the combined flow is neutralized with lime milk, which leads to irretrievable losses of non-ferrous metals with mud after neutralization. The use of the sulfiding method as part of the tactics of locally autonomous processing makes it possible to obtain the copper and zinc commercial products suitable for further metallurgical processing. Previously, sulphides of biogenic or chemical nature, as well as hydrogen sulphide, have been used in extraction of metals in the form of sulphides. In this study, we have used sulfur solution in sodium hydroxide with a mass ratio of NaOH:S = 1:1 as an alternative to the old reagents. During the study, the sulfur consumption for copper and zinc extraction were determined. The impact of water pH on zinc extraction is shown. The pilot-scale tests have confirmed the results of laboratory studies. Proposed is a flow chart with the following main operations: copper extraction, zinc extraction and the zinc product conditioning. Copper concentrate with a copper content of 32.9% and zinc concentrate with a zinc content of 48% were obtained. In the resulting deposits, copper is in the form of covellite (CuS), and zinc is in the form of sphalerite (ZnS). Through metal extraction was 99.9% for copper and 99.5% for zinc. DOI: