K2SO4 production via the double decomposition reaction of KCl and phosphogypsum

The production of potassium sulfate from phosphogypsum and potassium chlori de in the presence of ammonia and isopropanol has been investigated. The so lubility of phosphogypsum in aqueous solutions of KCl, HCl, and mixtures of both has been first measured at various temperatures and concentrations. T he factors affecting the conversion of potassium chloride to potassium sulf ate, such as aqueous ammonia to phosphogypsum ratio, weight percent of isop ropanol in the solution, weight percent excess phosphogypsum, and reaction temperature and pressure have also been investigated. The optimum reaction conditions obtained at 25 degrees C and atmospheric pr essure have been 50% excess phosphogypsum 4.32 ammonia solution to phosphog ypsum ratio, and aqueous solutions containing initial concentrations of 33 wt.% ammonia and 7 wt.% isopropanol. The maximum conversion of KCl to K2SO4 obtained under these conditions was 97.2%. (C) 2000 Elsevier Science S.A. All rights reserved.