Silicon and Quartz Recovery and Purification from Waste Quartz Crucible Ash with a Combined Process of Electric Separation and Hydrometallurgy

The efficient treatment of solid waste will play an increasingly nonnegligible role for sustainable development of the photovoltaic (PV) industry. Waste quartz crucible ash (WQCA) is an emerging solid waste with considerable silicon and quartz containing from monocrystalline silicon rod production by Czochralski method. However, the recycling and utilization of WQCA has not received attention from the industry at present. For this purpose, a combined process of electric separation and hydrometallurgy leaching rout was innovatively attempted for silicon and quartz recovery and purification from WQCA. The silicon enriched concentrate and quartz enriched tailing were obtained after electric separation, and then the concentrate and tailing were sent for two stages of acid leaching and alkaline leaching for impurity removal, respectively. After that, the silicon powder obtained from acid leaching was subjected to vacuum induction refining to prepare high-purity silicon casting product. The high purity silicon casting with impurity of 20.8 ppmw was successfully prepared from the silicon content of 75.604% in raw WQCA, as well as the high purity quartz powder was simultaneously obtained with content increase to 98.15% from 24.07% treated by this combined process. The two products obtained in this work are expected for high value-added products preparation after further purified and refined, which would be benefit to the green and sustainable development of the PV industry.