Silicon recovery from silicon–iron alloys by electrorefining in molten fluorides

Electrorefining of a silicon-iron material (Si–4.7at% Fe) in molten NaF-KF at 850°C was investigated in view of recovering pure Si, using electrochemical techniques, Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) and Inductively Coupled Plasma with atomic emission spectroscopy (ICP-AES) analyses. The selective electrochemical dissolution of Si was evidenced. Electrorefining runs led to a maximum recovery of 80% of Si initially contained in the material, in the form of a dense deposit at the cathode, with very high current efficiencies. The Si purity was examined and no Fe was detected by ICP-AES analysis: the recovered Si purity was assumed to be higher than 99.99%.