Effect of Thermal Pretreatment and Acid Leaching on the Removal of Boron from Metallurgical Grade Silicon
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The present work aims at investigating the impact of thermal pretreatment and acid leaching (HCl–HF) on the boron removal efficiency of metallurgical grade silicon (MG-Si). The impact of various parameters, involving oxidation temperature (700–1200 °C), oxidation time (1–5 h) and acid leaching (4 mol L−1 HCl–3 mol L−1 HF), on the removal of boron from MG-Si was thoroughly explored. It was found that thermal oxidation resulted in an enhanced removal efficiency of boron from MG-Si. By employing MG-Si particles in the range of 75–106 μm in conjunction with acid leaching at 65 °C for 6 h, the boron content was decreased from 19.60 to 14.10 ppmw, offering a removal efficiency of ca. 28%. When the MG-Si powder was subjected to thermal oxidation at 1100 °C for 5 h before leaching, the boron concentration in the purified Si was reduced from 19.60 to 8.90 ppmw, giving an extraction efficiency of 54.59%. An extended characterization study, regarding the microstructure, morphology and chemical composition of both un-treated and treated samples, was conducted to gain insight into the underlying mechanism of boron removal under different conditions.
KeywordsMetallurgical grade silicon Boron removal Thermal pretreatment Acid leaching
This study was supported by the National Natural Science Foundation of China (Nos. 51461027, 51334002) and Open Fund of State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization (No. CNMRCUTS1406).