Selective Separation of Arsenic from High-Arsenic Dust in the NaOH-S System Based on Response Surface Methodology

The selective separation of arsenic in the NaOH-S system from arsenic dust containing Pb, Sb, and Zn was studied by central composite design response surface method in this investigation. The results indicated that the presence of elemental sulfur can prevent lead and antimony leaching from arsenic dust effectively. The optimal leaching conditions were established as follows: 3.0 mol/L sodium hydroxide, 10 g/L sulfur, leaching temperature 95 °C, leaching time 2.0 h, liquid to solid ratio 6, and stirring speed 400 r/min. The arsenic leaching efficiency can reach 99.37% under the optimized conditions, meanwhile 98.39% of Sb, 99.74% of Zn, and 99.91% of Pb remained in the leach residue with the arsenic content < 0.1%. Oxidation-cooling crystallization has been used to recover sodium arsenate from the leaching solution under the optimal reaction conditions: C(H2O2)/C(As) 0.45, oxidation temperature 50 °C, stirring speed 200 r/min, crystallization temperature 30 °C, and crystallization time 120 min. This work presents a novel route for selective separation of arsenic and potential recycling lead and antimony from the arsenic dust in the NaOH leaching system with adding elemental sulfur.