Structure of Arsenic Sulfide Cake and Solubility of Its Alloys with Sulfur

摘要

This study investigates the possibility of recycling arsenic sulfide cakes by heat treatment with the addition of elemental sulfur. The structure of the initial cake as an X-ray amorphous dispersed arsenic sulfide with impregnations of lead sulfate and copper oxide is established. The main phases characterizing the microstructure of the cake are conglomerates of complex composition in the form of nonstoichiometric arsenic sulfide with inclusions of arsenic and copper oxides, as well as nonstoichiometric arsenic oxide with an admixture of arsenic and copper sulfides. Alloying of the cake with elemental sulfur ensures its compaction and vitrification. In the alloy samples, phases of nonstoichiometric arsenic sulfide and lead oxysulfate are detected. When the alloy is leached, the solubility of arsenic is below the threshold according to the TCLP method (i.e., 3.7-3.3 mg/dm(3)), which enables the burial of the material as ordinary waste.