LAUSR

Abstract Due to the local and global supersaturation of metal sulfides in aqueous solutions, the industrial metal sulfurization processes using soluble sulfur resources (Na2S/Na2S2O3/(NH4)2S/H2S) and elemental sulfur have insurmountable defects, including the unfilterable fine precipitates, weak chemical selectivity, high reagent toxicity, and generation of soluble polysulfides. In order to develop a cleaner and green sulfurization method, a surface/heterogeneous sulfurization system using wetted sulfur particles and sulfur dioxide was investigated through single-factor experiments and reaction mechanism tests. The results of disproportionation tests indicated that reaction parameters, such as temperature, powder contact angle, SO2 pressure and molar ratio of Cu-to-Sulfur, significantly affected the reaction efficiency. The reaction is mixed controlled by the temperature and powder contact angle. During the disproportionation‑sulfurization process, the total reaction rate for the generation of HS− ions is dependent upon: the liquid diffusion of SO2 absorption, the powder contact angle of wetted sulfur particles, and the nucleophilic reaction between SO3H− with sulfur. Meanwhile, the total reaction is a shrinking nuclear reaction which the particles sizes continuously increasing after the metal sulfides formed.