An alternative method for the treatment of metallurgical arsenic-alkali residue and recovery of high-purity sodium bicarbonate

Arsenic-alkali residue (AAR) is one of the major hazardous solid wastes produced by the antimony (Sb) smelter industry and may pose a serious threat to the local environment and public health. However, effective method for the treatment of AAR is still lacking. In this study, a new method for the effective treatment of AAR is proposed for the use of AAR from a Sb refinery. This treatment of AAR includes two-stage leaching of As and sodium carbonate with water, recovering of sodium carbonate as high-purity sodium bicarbonate (NaHCO3) via CO2 injection, and immobilizing As via Fe(III)-As(V) coprecipitation. The effects of the liquid/solid (L/S) ratio, temperature (25 degrees C vs. 80 degrees C), and leaching time on the leaching efficiency of As and sodium carbonate, and the recovery of NaHCO3 from AAR have been investigated. The results show that the As leaching efficiency is hardly affected by the L/S ratio and temperature, but the recovery efficiency of NaHCO3 is strongly controlled by the initial L/S ratio. The most suitable leaching efficiency of As (95.3%) from AAR is achieved with the L/S ratio of 2 at 25 degrees C during a 60 min reaction, while almost all metal(loids) such as Sb, Ca, Fe, and Zn remain in the leaching residues. The As content in the recovered NaHCO3 is as low as 0.040 g/kg, which can be directly used for Sb smelting. Synchrotron X-ray absorption spectroscopic analyses show that As in the recovered NaHCO3 occurs as incorporated species. Toxicity characteristic leaching procedure (TCLP) test of the Fe(III)-As(V) precipitates produced at the most suitable Fe/As molar ratio of 3 yields an As concentration of 1.3 mg/L, demonstrating that these precipitates from the new treatment method have good As stability and can be safely stored in the environment.

Automated summary

The study proposes a new method for the effective treatment of arsenic-alkali residue (AAR) from a antimony refinery, involving two-stage leaching and recovery processes. The results show high As leaching efficiency and low As content in the recovered NaHCO3, indicating good stability for safe storage and use. The method offers a promising solution for the management of hazardous solid wastes from the antimony smelter industry.