Recovery of silicon kerf waste from diamond wire sawing by two-step sintering and acid leaching method

Abstract

Silicon kerf waste from diamond-wire sawing of solar grade silicon is regarded as a promising resource for the clean production of high-purity silicon. In this study, silicon kerf waste is collected by a two-step sintering method (TSS) to obtain a ceramic product for the first time and its effect on the leaching behavior of silicon kerf was assessed. The results show that the relative density and grain size of silicon kerf ceramic could reach 91.72% and 0.75 μm under TSS3-10 h condition (1400 °C in the first stage and 1350 °C for 10 h in the second stage). The TSS process is confirmed to be beneficial for decomposing silicon oxide layer and promoting densification. Acid leaching experiment was conducted and the relationship between the relative density and impurity extraction was evaluated. It was found that the removal rate of impurities (except oxygen) from silicon kerf by direct acid leaching was higher than that through TSS3-10 h and acid leaching. However, the combined process can reduce 52.4% oxygen content and the yield of silicon was reached 96.03%. The present study aims to shed light on the feasible application of TSS on the hydrometallurgical recycling of silicon kerf.