Green Route to Arsenic Detoxification: Mechanochemical Transformation of As₂O₃ to As(0)

Abstract

With the continuous exploitation of arsenic-containing resources and growing concern over arsenic contamination, the disposal of arsenic has become a global challenge. Elemental arsenic, because of its nontoxic nature, is considered a preferred form for arsenic detoxification and mitigation. We introduce an innovative and eco-friendly method to convert the highly toxic arsenic trioxide into nonpoisonous elemental arsenic via a mechanochemical processing at room temperature. Utilizing zinc powder as the reductant and acetic acid as the reaction medium, we achieved a remarkable reduction efficiency of 92.5%, producing elemental arsenic of approximately 99% purity. Thermodynamic analysis revealed the pivotal role of acetic acid in stabilizing the reaction system and eliminating the formation of arsine. Density functional theory calculations further confirmed that the reduction of H3AsO3 on the zinc surface was the dominant reaction in the Zn–CH3COOH–As2O3 system. The introduction of mechanical force lowered the relative energy of the reaction, resulting in superior reduction performance under relatively mild conditions. These findings could pave the way for the safe disposal of arsenic-containing waste and offer a sustainable route to reducing the toxicity of arsenic trioxide.