Process for purifying Moroccan phosphogypsum
by a combined sulfuric acid and aluminum salt treatment
H. Nasrellah, A. Loudiki, L. El Gaini, J. El Hajri, M. El Krati, K. Benkhouja, M. Bakasse*
Laboratory of organic chemistry, bioorganic and Environmental;
Faculty of Sciences; University Chouaib Doukkali-El Jadida - Morocco
* Corresponding author. E-mail: firstname.lastname@example.org
Received: 15 July 2014; revised version accepted: 19 September 2014
Phosphogypsum is derived from the dissolution of phosphate in sulfuric acid. In this study, we studied purification of hosphogypsum by dehydration of anhydrite using of aluminum salt as an activator at room temperature. The anhydrite crystal is first obtained through dehydration of phosphogypsum in strong sulfuric acid 67%. The anhydrite is then rehydrated to gypsum by adding sulfuric acid 10% and an activator Al2(SO4)3, 18H2O at different portion. Under these conditions phosphogypsum was formed mainly of gypsum and little anhydrite. By not converting all phosphogypsum on the anhydrite crystal, the radium and heavy metals contamination remains on the anhydrite of a size on the order of about 1-25 micrometers. Separation of anhydrite from gypsum was performed by separation by humid sieving. The gypsum formed has been characterized using chemical gravimetric analyses, X-ray diffraction, Scanning Electron Microscopy (SEM) and Thermal analyses performed by gravimetric method, Infra red spectra and ICP analysis.
Keywords: Phosphogypsum; Gypsum; Anhydrite; Hydrate; Wet sieving.