Process and mechanism of hydrothermal stabilization for arsenic sulfide sludge containing elemental sulfur

Abstract

An optimized hydrothermal treatment was employed to stabilize the arsenic sulfide sludge (ASS). Under the optimal conditions (160 °C, 2 h, liquid-to-solid (L/S) ratio of 1:1, and initial pH of 2), the leaching concentrations of As and Cd decreased from 504.0 and 12.0 mg/L to 1.23 and 0.03 mg/L of the treated ASS, respectively. The results indicate that the stabilization of the ASS was achieved through structure transformation from the particles into a bulk and the speciation transformation of As and Cd. Besides, sulfur in the ASS could significantly improve the stabilization property due to its melting and polymerization.