Solvent refining of silicon from Al-Si melts assisted by a centrifugation was investigated for three alloys in the Al-Si system. Silicon was successfully separated from aluminum-rich phase in the form of a foam by centrifugation. As the silicon content increased, the recovery decreased because less aluminum-rich phases remained in the silicon foam. The weight ratio before and after acid leaching of the silicon foam was inversely related to its apparent density before acid leaching. The purity of the extracted silicon decreased slightly with increased silicon content. The purity of the silicon flakes obtained from the Al - 30% Si alloy was 4N, except aluminum. Boron and phosphorus in the silicon flakes could be lowered effectively by decreasing the silicon content in the Al-Si alloys

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A new way to melt and refine recycled silicon powders from the wafer back grinding wastes was proposed. We designed a new equipment using induction heating for the fast melting and directional solidification of the recycled silicon powders, and investigated the feasibility of utilizing them as silicon feedstock for solar cells through lab-scale experiments on the melting and refining them. Silicon particles recovered from back grinding slurry were flake like and very fine, about 3um and was covered with very thin silicon oxide. Slag was observed on the top of the melt during melting, which was composed of oxygen, silicon and carbon which was believed to come from the graphite crucible. Complete melting and subsequent feeding of powders into the melt were prevented by the slag formed during melting, which could be solved by changing the melting atmosphere. Slow growth rate made the impurities such as Al, Ti, Fe, Zr segregate to the top of the ingot purifying the lower part. Over 5N purity was obtained in the middle and lower part of the ingot by the fast melting and directional solidification.