Mechanism of enhancing Fe removal from metallurgical grade silicon by metal-assisted chemical leaching

In this study, the mechanism of enhancing Fe removal from metallurgical grade silicon (MG–Si) by the novel metal-assisted chemical leaching (MACL) purification methods have been investigated. The typical impurity phase Si2Fe was selected to study interface reactions between the impurity phase and lixiviant. Based on density functional theory (DFT), the interactions of HF leaching, CuACL and AgACL on Si2Fe were revealed through studying the evolution behaviors of atom geometric structure, density of states and bond population, which showed that the stability of Si2Fe structure weakened with the orders of AgACL > CuACL > HF leaching. It was found that the lengths of Si–Fe bonds and metallicity of Si2Fe were successively increased when Si2Fe interacted with HF leaching, CuACL and AgACL, respectively. Compared with HF leaching, MACL weakened Si–Fe bond populations and increased HFe bond populations, further destroyed the stability of Si2Fe structure. The experimental results showed that the impurity Fe removal rates were 94.30% for HF leaching, 95.75% for CuACL, and 97.27% for AgACL, respectively, which was highly consistent with the theoretical simulation results. The study provides a theoretical basis for enhancing Fe removal from silicon through MACL produces, indicating that MACL methods have a potential application in deep removal of impurity Fe from silicon in the future.