A novel scheme for safe disposal and resource utilization of arsenic-alkali slag

Abstract As solid waste posing a great threat to the environmental system, the disposal of arsenic-alkali slag has become the top priority in the development of the antimony industry. In this paper, a novel technological scheme combining the advantages of chemical precipitation and fractional crystallization is proposed for the safe disposal and resource utilization of arsenic-alkali slag. The scheme is mainly composed of three parts, namely, leaching of arsenic-alkali slag, selective removal of arsenic in the arsenic-alkali solution, and evaporation crystallization of alkali solution. In the leaching part, the optimum leaching parameters are determined by orthogonal tests. In the arsenic and alkali separation part, based on thermodynamic analysis, the selective removal of arsenic from arsenic-alkali solution is realized by forming ammonium magnesium arsenate (MgNH4AsO4) precipitation. In the evaporation crystallization part, the crystalline product with sodium carbonate (Na2CO3) content of 89.87% is obtained by the evaporation crystallization experiment. The whole process does not produce secondary pollution and realizes the reuse of wastewater. The final products are leaching residue, arsenic slag, and sodium carbonate with an arsenic content of 0.83%, 24.93%, and 0.18%, respectively.