Fundamental study on recovery of resources by magnetic separation using superconducting bulk magnet

The process of polishing glass substrate is necessary for production of the liquid crystal, thus the substance which mainly consists of CeO2 (ceria) is used as a polishing agent. In this study, we aim to separate impurities selectively from waste slurry and recover ceria particles in order to reuse as a polishing agent. Waste fluid contains impurities such as ferrous particles originating from aggregating agent. We focused on the difference in magnetic property of each particle, and applied the high gradient magnetic separation with superconducting magnet which can separate not only ferromagnetic particle but also paramagnetic particle with relatively high magnetization. We controlled pH based on surface potential of ceria and ferrous particles in order to avoid the aggregation of the waste fluid. As the result of optimization of the conditions such as the geometry of filters, fluid flow rate and pH by calculation and experiment, the sufficient separation efficiency was obtained.