Silicon (Si) waste and use of large amount of acid restrict the application of metallurgical grade silicon purification by Si-Al alloying process. To increase the recovery rate of primary Si, the effects of metal tin (Sn) addition on the recovery rate of primary Si were investigated in 31.86 at% Si-Al alloy. The actual recovery rate of primary Si is about 83% in Si-Al-Sn alloy with 10 at% Sn addition, which is higher than that of the 31.86 at% Si-Al alloy (62%). Sn addition tends to produce primary Si dendrites with larger widths. With the agglomeration of primary Si by Lorenz force considered, Sn addition is significant not only for resource recycling but also for environmental protection because of the reduced amount of acid used in the process. The impurities in primary Si and the impurity distribution in alloys were analyzed by inductively coupled plasma-mass spectrometry and electron probe microanalysis, respectively. Results show that Sn addition was favorable for the collection of boron in the Si-Al-Sn phase. (C) 2013 Elsevier B.V. All rights reserved.