Comparative study of K2SO4 production by wet conversion from phosphogypsum and synthetic gypsum

Abstract

This paper proposes a very attractive process for K2SO4 production via the wet conversion of phosphogypsum (PG) and K2CO3. A parallel study of the conversion of two synthetic types of gypsum by K2SO4 was performed in order to compare their reactivity with that of PG.We remark that PG is more reactive and yields the desired results while commercial types of gypsum react slowly and generate unwanted secondary products. The factors affecting the PG conversion processes such as the initial concentration of reagents, the reaction time and the reaction temperature was studied to optimize the reaction conditions. X-ray diffraction (XRD) was used to characterize the PG conversion at different conditions while the other techniques (Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), scanning electron microscopy (SEM), flame photometer (FP), inductively coupled plasma mass spectrometry (ICP-MS) and thermogravimetric analysis (TGA)) were applied to prove the quality of the final products.Based on the obtained results, the reaction is carried out with stoichiometric proportions between PG and K2CO3. The maximal conversion of PG is attained at 80 °C; this temperature corresponds to the higher solubility of K2SO4, which is 1.2 mol/l. Keywords: Wet conversion, Phosphogypsum, Potassium sulfate, Calcite, Synthetic gypsum, Syngenite