Producing High Quality CaCO<sub>3</sub> 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 CaCO 3 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 NH 3 ·H 2 O respectively. The purity and whiteness of CaCO 3 produced by the carbonization of purified CaCl 2 solution are 98% and 96%. The optimum mass ratio of phosphogypsum, NaOH and HCl was 25:12:35. Chemical characterization of the resultant CaCO 3 was performed by XRD, SEM, TG and chemical titration method, which indicate that this method is effective in producing spherical CaCO 3 at room temperature, moreover, the purity, whiteness and thermostability of calcium carbonate can meet most of application requirements for industrial CaCO 3 .