Stabilization mechanism of arsenic-sulfide slag by density functional theory calculation of arsenic-sulfide clusters

Stabilization of arsenic sulfur slag (As-S slag) is of high importance to prevent the release of deadly As pollutants into environment. However, the molecular understanding on the stability of As-S slag is missing, which in turn restricts the development of robust approach to solve the challenge. In this work, we investigated the structurestability relationship of As-S slag with adopting various As-S clusters as prototypes by density functional theory (DFT). Results showed that the configuration of S multimers-covering-(As2S3)n is the most stable structure amongst the candidates by the analysis of energies and bonding characteristics. The high stability is explained by orbital composition that the 4p-orbital (As) binding with 3p-orbital (S) decreases energy level of highest occupied molecular orbital (HOMO). Inspired from the calculations, an excess-S-based hydrothermal method was successfully proposed and achieved to promote the stabilization of As-S slag. Typically, the As concentration from the leaching test of stabilized As-S slag is only 0.8 mg/L, which is much lower than the value from other stabilized slag.

Automated summary

Stabilization of arsenic sulfur slag is crucial to prevent environmental pollution, but the molecular understanding of its stability is lacking, hindering the development of effective solutions. By studying the structure-stability relationship of As-S slag, the most stable structure was identified and a successful excess-S-based hydrothermal method was proposed to promote stabilization. This method significantly reduced the arsenic concentration in the leaching test, demonstrating its effectiveness compared to other methods.