Improving the precipitation of arsenic trisulfide from washing waters of sulfuric-acid production of copper smelteries

Abstract

Disadvantages of the sulfide method of purifying washing waters of the sulfuric-acid production are the formation of finely dispersed (particle size from 0.3 to 1.5 μm) difficult-to-filter precipitates of arsenic(III) sulfide and the danger of isolation of hydrogen sulfide into the atmosphere upon an overdose of sodium hydrosulfide. The coagulation of sols of arsenic sulfide is investigated in order to develop more efficient and rapid filtration technology of the precipitate. The filtration rate in various supply modes of sodium hydrosulfide and the dependence of settling rate and filtration on the presence of coagulants such as iron sulfate and aluminum sulfate are determined. It is established that the implementation of the distributed supply of sodium hydrosulfide during the precipitation of arsenic sulfide in combination with the application of such inorganic coagulant as iron(III) sulfate will make it possible to increase the particle size of the As₂S₃ phase by a factor of several times and increase the filtration and settling rates of pulps.