Growth behavior of heavy metal sulfide particles: A comparison between gas-liquid and liquid-liquid sulfidation

Abstract

Sulfide precipitation is an effective method for treating acidic heavy metal wastewater. However, the process often generates tiny particles with poor settling performance. The factors and mechanisms influencing particle size and settling performance remain unclear. In this study, the growth behavior of CuS particles generated by two sulfide precipitation methods, gas-liquid and liquid-liquid sulfidation, was investigated. The effects of acidity, sulfur-to-copper molar ratio, and temperature on particle size were analyzed. The results showed that increasing the temperature had an adverse effect on CuS particle growth. Additionally, we found that acidity and sulfur-to-copper molar ratio had a more significant impact on particle growth in the liquid-liquid sulfidation system than in the gas-liquid sulfidation system. Based on supersaturation calculations and XPS analysis, it is found that particle growth in gas-liquid sulfidation systems is mainly influenced by supersaturation, while particle growth in liquid-liquid sulfidation systems is mainly affected by surface charge. This study provides valuable insights into the factors that influence particle growth in sulfide precipitation and can inform the development of strategies to improve the effective precipitation of sulfide nanoparticles in acidic wastewater.