OZONE WHITENING OF SYSTHETIC GYPSUM

摘要

Crude gypsum from H2SO4 treatment of phosphate rock is bleached in aq. suspension by treatment with ozone. Thus, an aq. suspension contg. 30 wt.% finely ground phophogypsum with a whiteness of 64 is stirred at room temp. and the pH3 suspension is treated 1 hr with 100 gas contg. 5 g ozone(600 ppm relative to phosphogypsum in the suspension). The resulting product has a whiteness of 77 and is suitable as a filler for the paper industry.