Abstract

Arsenic-alkali leaching residue (AAR), generated during antimony smelting, is a hazardous solid waste containing arsenic and antimony. Its safe disposal and resource-oriented utilization are constrained by the strong stabilization of As- and Sb-bearing species in a high-alkali matrix. Herein, we investigated the alkali locking effect during carbothermal roasting of AAR and proposed a SiO2-assisted roasting strategy to promote the simultaneous volatilization of arsenic and antimony. Thermodynamic calculations indicate that, in a sodium-rich roasting system, representative As- and Sb-bearing species preferentially transform into thermodynamically stable Na3AsO4 and Na3SbO4, thereby suppressing their reductive conversion into volatile As2O3 and Sb2O3. Direct roasting experiments confirmed that simply increasing roasting temperature, carbon dosage, or roasting time was insufficient to achieve efficient simultaneous volatilization of As and Sb, which experimentally supports the existence of the alkali-locking effect. The introduction of SiO2 weakened sodium-induced immobilization by favoring the formation of sodium silicate phases, thereby enhancing the thermodynamic driving force for the generation and release of As2O3 and Sb2O3. Under the conditions of 900 °C, 90 min, 30% carbon dosage, and 10% SiO2 addition, the volatilization rates of arsenic and antimony reached 93.25% and 93.80%, respectively. XRD and SEM-EDS revealed that the addition of SiO2 promoted the reconstruction of Na–Al–Si-bearing phases and the development of porous slag structures, thereby facilitating the mass transfer and volatilization of As/Sb species. Preliminary co-roasting experiments with flotation antimony concentrate suggest the feasibility of using Si-bearing gangue as an in situ additive for AAR treatment. This study provides a thermodynamic and experimental basis for the resource-oriented detoxification of arsenic-alkali leaching residue.

Keywords