Current processing technology for antimony-bearing ores a review, part 2

Abstract

On the basis of knowledge of the beneficiation properties of antimony minerals reported in the previous part of this article, this second half reviews the state of technology for separation of those minerals and summarizes experience from processing plants. The high density of antimony minerals and their tendency to grind to slime (hardness of 2.5 on Mohs' scale) make gravity separation in the mill circuit an interesting possibility for the first step in the process. Gravity concentration is already found in some process layouts, but there are undoubtedly more applications where modern gravity separation equipment could be used. Marketing considerations make separation of arsenopyrite an important part of the process in some cases. Special cleaning processes have been developed for the purpose, but more attention needs to be paid to selectivity in the primary Sb flotation. Because of the rise in gold prices, some antimony ores should really be viewed as gold ores with antimony as a by-product. In this context, cyanide leaching is an obvious step in addition to gravity separation, and the most logical procedure here would be first to separate the antimony at natural pH and then to leach out the gold with cyanide. The design of flotation circuits for beneficiation of stibnite is usually very straightforward: rougher, scavenger and two-stage cleaner flotation are usually enough to produce concentrates grading better than 60% Sb. Recycling circulating returns to the middle of the rougher flotation circuit offers an attractive way of obtaining high-grade concentrates while achieving high capacities. The choice of methods for depressing antimony minerals in complex sulphide ores depends on what kind of mineral is the predominant impurity. It ought to be possible to depress ferrous antimony minerals effectively in pyrite-selective environments.