Eco-friendly extraction of arsenic and tungsten from hazardous tungsten residue waste by pressure oxidation leaching in alkaline solutions: Mechanism and kinetic model

Tungsten residue waste (TRW), considered an environmental burden due to high content and excessive leaching toxicity of arsenic (As), are also secondary tungsten (W) resources. A novel method for simultaneous extraction of arsenic and tungsten from TRW via alkaline pressure oxidative leaching was proposed. The results show that As in the TRW mainly exists in the form of As coprecipitated with Mn(II) oxides and FeAsS. In addition, As coprecipitated with Mn(II) oxides and W are encapsulated in Fe, Mn oxides. The structure of Fe, Mn oxides with dense surface can be destroyed and the chemically stable arsenopyrite can be efficiently oxidized by oxygen in alkaline solutions. The leaching efficiency of As and S reached 97% and 99% at 80 min, respectively, while that of W reached 82% at 10 min. The leaching rate of As and S is controlled by diffusion with the apparent activation energies of 16.67 kJ/mol and 15.66 kJ/mol, respectively. Compared with TRW, the leaching toxicity of As in the leach residue decreased from 10.2 mg/L to only 0.071 mg/L. The new process suggests new possibilities for removal and recovery of As and W from TRW that will contribute to circular economy and environmental protection.