Removal of Phosphate from Wastewater by Adsorption on Marble Waste: Effect of Process Parameters and Kinetic Modeling

Batch adsorption experiments were carried out, aiming to remove phosphates ions from water samples using powdered marble (PWM) as an effective inorganic sorbent, which is cheap, widespread. Operating parameters such as pH, sorbent, and phosphates concentration, shaking time, and temperature influencing the sorption process, were investigated. The results obtained showed that the sorption of phosphates ions onto PWM was fitted well with the linear Langmuir model over the concentration range studied. Phosphate removal by PWM was a pH-dependent process. Mechanisms for phosphate removal mainly involved adsorption and precipitation, varied with equilibrium pH of the solution. The sorption on PWM increased with increasing temperature. The pseudo-second-order model characterized the kinetics of the removal process by PWM adsorbent. The synthesized adsorbents before and after phosphate adsorption were characterized by powder X-ray diffraction and Fourier-transform infrared spectroscopy. The calculated thermodynamic parameters (∆G°, ∆H°, and ∆S°) showed that the adsorption of phosphate onto powdered marble was feasible, spontaneous and endothermic at 15–40 °C.