Abstract:To achieve a safe treatment of arsenic-containing acid wastewater, a new process was proposed, including arsenic removal via sulfide precipitation and hydrothermal mineralization stabilization. Under optimal conditions of sulfide precipitation, 99.65% of arsenic from wastewater was precipitated in the form of amorphous As₂S₃. The As leaching concentration of amorphous As₂S₃ in TCLP (toxicity characteristic leaching procedure) test was up to 212.97 mg/L, therefore, hydrothermal mineralization was adopted to improve the stability of amorphous As₂S₃. The results showed that the As leaching concentration of mineralized As₂S₃ was only 4.82 mg/L. Furthermore, the amorphous As₂S₃ could be transformed into crystallized As₂S₃ (orpiment) in the presence of mineralizer Na₂SO₄. Simultaneously, the As leaching concentration of crystallized As₂S₃ was further reduced to 3.86 mg/L. Hydrothermal mineralization was an effective method for the stabilization of As₂S₃. Therefore, this process has a greater application in the treatment of arsenic-containing wastewater.

Key words: arsenic-containing wastewater; arsenic removal; stabilization; sulfide precipitation; hydrothermal mineralization; hydrothermal crystallization