Phosphogypsum utilization - part II: Preparation of ammonium sulphate

The aim of this work was to describe the conversion of raw phosphogypsum, issued from the manufacture of H3PO4 by dissolving the phosphate rock in H2SO4, into (NH4)(2)SO4 and CaCO3. The thermal analysis technique was used to estimate the yield of conversion. (NH4)(2)CO3 or (NH4)(2)CO3 with excess NH4OH or (NH4)(2)CO3 with NH3 gas were used in the preparation of (NH4)(2)SO4 from phosphogypsum. The obtained samples were separated and tested by chemical and thermogravimetric analyses, infrared spectrum and X-ray diffraction and the optimum conditions of conversion were determined. The results indicated that the yield of conversion equals to 83.37 and 86.70% in case of using (NH4)(2)CO3 or (NH4)(2)CO3 with excess ammonia respectively, while by using NH3 gas the percentage of conversion increased to 94.2% at a flow rate of 6 ml/min. Chemical analysis, infrared spectrum and X-ray diffraction patterns of the yield, (NH4)(2)SO4 were nearly similar to the standard sample.