Removal of Chromium (III) from Monoammonium Phosphate Solutions by a Porous Adsorbent of Fluor(calcium silicate) Composites

The products of monoammonium phosphate containing Cr3+ resulted in disqualification, and further posed a serious threat to ecological environment and human beings. Herein, the porous adsorbent of fluor(calcium silicate) composites (FCSc) was prepared by hydrothermal method using diatomaceous earth, hydrated lime and additive (NaF) as raw materials, which was characterized and used for the removal of Cr3+ from monoammonium phosphate solutions. The effects of different parameters, such as solution pH, initial Cr3+ concentration, temperature and contact time on the adsorption of Cr3+ onto FCSc were investigated in details. The results indicated that the adsorption process was in agreement with the pseudo-second-order kinetic model and Freundlich isotherm. The spontaneous and endothermic nature of the adsorption process was obtained by analyzing various thermodynamic parameters (Delta G(0), Delta H-0, and Delta S-0). In addition, computational monte carlo simulations between Cr3+ ions and FCSc were conducted to elucidate the adsorption mechanism. Such kind of porous adsorbent provided a potential application in the removal of impurities from monoammonium phosphate industry.