| 摘要 |
An improved method for improving the brightness of clay of the type that is capable of being bleached by an oxidative reagent, such as Georgia gray kaolin. Such clay, in the form of a dispersed slurry, is treated with a combination of an inorganic condensed phosphate, sodium hypochlorite and ozone, preferably including separate treatment steps of magnetic purification and reductive bleaching. Suitable phosphates include sodium hexametaphosphate, sodium tripolyphosphate and tetrasodium pyrophosphate. The hypochlorite is added shortly before ozonation, and the phosphate is added before, simultaneously with, or after the hypochlorite.
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