Sorption thermodynamic and kinetic studies of Lead removal from aqueous solutions by nano Tricalcium phosphate

Abstract

Nano tricalcium phosphate particles were prepared by a wet method from aqueous solutions and characterized using TEM, XRD, and BET-N2 adsorption measurements. The potential of the synthesized nano tricalcium phosphate particles to remove Pb2+ cations from aqueous solutions was investigated in batch reactor under different experimental condition. The effects of initial concentration, adsorbent dosage, contact time and temperature were studied in batch experiments. The sorption of Pb2+ by nano-TCP increased as the initial concentration of lead ion increased in the medium. Various thermodynamic parameters, such as G°, H° and S° were calculated. Thermodynamics of Pb2+ cation sorption onto nano-TCP system pointed at spontaneous and endothermic nature of the process. The pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models were applied to study the kinetics of the sorption processes. The pseudo-second order kinetic model provided the best correlation (R2 > 0.999) of the used experimental data compared to the pseudo-first order and intraparticle diffusion kinetic models. The maximum Pb2+ adsorbed was found to be 4761.90 mg/g. It was found that the sorption of Pb2+ on nano-TCP was correlated well (R2 = 0.982) with the Langmuir equation as compared to Freundlich and Dubinin–Kaganer–Radushkevich (D-K-R) isotherm equation under the concentration range studied. This study indicated that nano-TCP could be used as an efficient adsorbent for removal of Pb2+ from aqueous solution.