Recovery of cerium oxide

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PROBLEM TO BE SOLVED : To provide a cerium oxide recovery method that enables abrasive waste generated in polishing of a glass substrate to be recovered and recycled as a less-impurity abrasive which is composed mainly of cerium oxide and can be used to polish a synthetic quartz glass substrate for state-of-the-art semiconductor applications including photomasks and reticles, and that results in suppression of the supply instability of cerium being a precious rare earth.SOLUTION : There is provided the method for recovering cerium oxide from the abrasive waste composed mainly of cerium oxide generated in the polishing of glass substrates, the method comprises : (i) adding to the abrasive waste an aqueous solution of an alkali metal hydroxide; (ii) adding to the resulting solution a sedimentation agent, thereby forming precipitates composed mainly of cerium oxide, and removing the supernatant liquid; (iii) adding to the resulting precipitates a solution of an acid substance, thereby making the precipitates slightly acid to neutral; (iv) washing the precipitates with an organic solvent; and (v) drying and crushing the precipitates.