In order to strengthen B removal during purification of Si with Al-Si solvent, small amounts (<1100 ppma) of transition metals (Hf, Zr, Ti, and Nb) were employed as additives because of their strong affinity for B. The results showed that the B removal process can be significantly improved by adding small amounts of Hf, Zr, and Ti and that Hf and Zr are more efficient for strengthening B removal than Ti or Nb. Nb had no effect on B removal. These additives could be also efficiently removed because of their extremely small segregation coefficients. (c) 2016 Elsevier B.V. All rights reserved.