Thermal treatment of mixtures of Tunisian phosphorite and additives of aluminum silicate

The process in the mixtures of Tunisian phosphorite (TP) with addition of aluminum silicate waste by chemical and X-ray diffraction (XRD) analyses was studied. The influence of the additive's quantity, the temperature of thermal treatment, as well as the mechanical activation on the solubility of the heated mixtures in various extracting agents (citric acid, ammonium citrate and formic acid), were investigated. The solubility Of P2O5 is higher in the case of the calcined and mechanically activated TP and its mixtures with "Medet's steryl" (MS) compared to the non-activated TP and its mixtures. The activated mixtures with 20% of MS have highest rate Of P2O5 solubilization in citrate acid (66%) as well into ammonium citrate soluble form (60%). New phases [Ca-5(PO4)(3)(OH), Ca-5(PO4)(2)(SiO4)-Si-., Ca-7(PO4)(2)(.)(SiO4)(2) and Ca4P2O9] in non-activated and activated calcined products were determined using XRD analysis. (C) 2003 Elsevier Science B.V. All rights reserved.