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Producing High Quality CaCO3 by Phosphogypsum with New Ammonia-Base Carbonation Method

Phosphogypsum is a by-product of industrial phosphoric acid producing with wet method, a simple and efficient way to produce high quality CaCO3 by phosphogysum is presented in this work. Calcium in the phosphogypsum converts into Ca (OH)2 with the addition of NaOH, acid insoluble substances and metal ion which was also separated from calcium in phosphogypsum by HCl and NH3·H2O respectively. The purity and whiteness of CaCO3 produced by the carbonization of purified CaCl2 solution are 98% and 96%. The optimum mass ratio of phosphogypsum, NaOH and HCl was 25:12:35. Chemical characterization of the resultant CaCO3 was performed by XRD, SEM, TG and chemical titration method, which indicate that this method is effective in producing spherical CaCO3 at room temperature, moreover, the purity, whiteness and thermostability of calcium carbonate can meet most of application requirements for industrial CaCO3.