Separation of elemental sulfur from zinc concentrate direct leaching residue by vacuum distillation

•Recovery of sulfur from direct leaching residue by vacuum distillation is feasible.•Sulfur recovery rate and purity can be higher than 98.0% and 97.8%, respectively.•Sulfur evaporation at 200 °C was negligible as pressure was higher than −0.08 MPa.•Sulfur recovery rate under −0.10 MPa increased exponentially from 140 to 220 °C.

Properly disposal and reutilization of direct leaching residue (DLR) from metal production industries can reduce environmental pollution as well as better conserve resources. In this study, recovery of elemental sulfur from zinc concentrate DLR using vacuum distillation was thoroughly investigated. The results show that elemental sulfur recovery using vacuum distillation was over 98% with a high purity under optimized conditions. The low temperature requirement (200–300 °C) of vacuum distillation may reduce the energy consumption comparing to traditional distillation under ambient pressure. Effects of parameters (distillation time, vacuum, temperature, particle size and distillation area) on sulfur recovery rate were presented. High sulfur recovery rate was observed with relative pressure lower than −0.09 megapascal (MPa). Sulfur recovery rate increased sharply with temperature in the range of 140–220 °C, while temperature above 220 °C only slightly promoted sulfur recovery. Smaller DLR particle size and larger distillation area facilitated mass and heat transportation, and resulted in higher sulfur recovery rates. The vacuum distillation separation technology reveals an alternative method to efficiently and economically separate elemental sulfur from zinc concentrate DLR. The impacts of operation parameters on the sulfur recovery rate were well documented in this study, and they are important for further optimizing the process and strategically applying the technology in a larger scale scenario.