A metallurgical route to upgrade silicon kerf derived from diamond-wire slicing process

Silicon kerf generated during the diamond-wire slicing process contains various impurities and are considered industrial waste. In order to utilize the waste, a feasible process to purify silicon kerf by a combination of slag treatment and acid leaching was developed. The results demonstrated that the Na2OSiO2 slag refining can effectively enhance the yield of the silicon kerf, and the Si yield was found to be 63.2%. The combined processes were able to reduce the total concentration of major impurities (Fe, Al, Ca, Ni, B, and P) from 6998 to 58 ppmw with a removal efficiency of 99.2%. The purity of the recovered Si was upgraded to from 93.3% to 99.98%. The mechanism suggests that impurity removal was facilitated by both the oxidation and the segregation of impurities to intermetallic precipitate phases. These precipitates can then be eliminated by acid leaching, and the extraction process of metallic impurities was mainly dominated by the surface chemical reaction.