Application of Acid Activated Bentonite for Efficient Removal of Organic Pollutants from Industrial Phosphoric Acid: Kinetic and Thermodynamic Study

Environmental and health issues are critical challenges for sustainable development in the 21st century; therefore, this paper investigates a simple and cost-effective process for recovery of organic matter (OM) from phosphoric acid to provide environmentally acceptable P-fertilizer. This study analyzed the structural transformations and adsorption properties of Na-bentonite clay before and after chemical activation by sulfuric and hydrochloric acids. The untreated and treated clay samples have been used for adsorption of organic matter from high strength phosphoric acid. The experimental data exhibited that the clay treated with sulfuric acid caused highest organic matter adsorption capacity. The kinetic models of adsorption were analyzed by the pseudo-first order, pseudo-second order, Elovich kinetic and Morris-Weber models. The results indicated that the pseudo-second-order kinetic model is more appropriate than the others for natural bentonite; but, for chemical activated clays, pseudo-first order is fitting. Obtained adsorption thermodynamic parameters (ΔH°, ΔS°, and ΔG°) expose that the organic matter adsorption is an endothermic, physical, and spontaneous process.