Search

Arsenic-alkali slag (AAS) is one of the most hazardous solid wastes generated by the antimony smelting process, posing a significant environmental risk. However, the economic method for effective As immobilization in AAS is still lacking. In this study, we proposed an economical and novel method for the removal of As from AAS using siderite (FeCO3). After the sodium carbonate is recovered from the AAS leaching liquor, the process continues. Aqueous As(V) is immobilized as scorodite via continuous dissolution–oxidation of siderite (FeCO3) by air injection. The residual As(V) is immobilized via Fe-As coprecipitation by lime neutralization. The dissolution–oxidation of siderite produces Fe(III), ensuring continuous Fe(III)-As(V) coprecipitation and scorodite crystallization. The results showed that the removal efficiency of As from AAS reached 99.98%. The mixture of scorodite and Fe-As coprecipitation demonstrated good As stability in the Toxicity Characteristic Leaching Procedure (2.6 mg/L) and at pH 4 (1.84 mg/L), pH 6 (2.13 mg/L), and pH 8 (3.20 mg/L) in a 50-d long-term stability test. Combined results from chemical analysis, X-ray diffraction, and infrared spectroscopy revealed that the existence of high ionic strength Na+ and Cl– were the critical factors in the dissolution of siderite and the crystallization of scorodite. This study provides an effective treatment method for the removal and fixation of arsenic in metallurgical AAS. [ABSTRACT FROM AUTHOR]