Reduction mechanism of spent ITO target in CaCl2 molten salt

In-Sn alloys were recycled by direct reduction of spent ITO (s-ITO) target in molten calcium chloride at 850 degrees C. The electro-deoxidation mechanism of s-ITO was investigated by electrolysis at different voltages and different electrolysis times. In the electro-deoxidation process, s-ITO was first formed with CaO to form CaIn2O4, CaSnO3 and Ca2SnO4, and then it was reduced into In-Sn alloy. Under constant voltage electrolysis at 2.2 V for 3 h, 2 g of s-ITO can be completely reduced to indium-tin alloy. Various contents of CaO were added to molten salt to study the effect of CaO on the reduction process. After immersing the s-ITO block in CaCl2 and CaO-CaCl2 for different times, it was found that the addition of CaO inhibited the dissolution of s-ITO. Potentiostatic electrolysis was performed in CaCl2 containing 0-3 mol% CaO for 3 h, and it was investigated that with the increase of CaO content, the alloy yield increased, while the current efficiency gradually decreased.