Silicon recycling and iron, nickel removal from diamond wire saw silicon powder waste: Synergistic chlorination with CaO smelting treatment

Abstract

During the processing of silicon wafers for photovoltaic power generation, nearly 30–40% of silicon ingot will be lost as diamond wire saw silicon powder (DWSSP) waste; this can result in reduced profits, potential danger, and environmental pollution. Driven by the rapid development of the photovoltaic industry, the demand for high-purity silicon and the production of silicon waste generated during silicon processing will continue to increase. Againstthistrend, the recycling of silicon from DWSSP waste is a desirable alternative to meet the growing demand for high-purity silicon. In this study, a novel process of chlorination with CaO smelting treatment is first proposed for the recycling of silicon and the removal of Fe and Ni from DWSSP waste. The results of this research indicate that the SiO2 shell can be absorbed by the added CaO, while eutectic NaCl-MgCl2 has a significant effect on the maximum recovery of silicon by reducing the viscosity of the molten slag and the removal of metals through the micro concentration cells. CaO and eutectic NaCl-MgCl2 play a synergistic role in the promotion of silicon separation and the removal of Fe and Ni. Silicon with a purity of 99.83% and a recovery rate of nearly 98.96% was obtained under the smelting conditions of DWSSP:CaO:NaCl:MgCl2 = 150.0:23.42:7.50:8.85 with a holding time of 2 h at 1823 K. This process overcomes the technical bottleneck of the removal of Fe and Ni via smelting treatment, which is favorable for the recycling of silicon from DWSSP waste at the industrial scale.