Removal of Pb(II) from aqueous solution by hydroxyapatite/carbon composite: Preparation and adsorption behavior

The present work exhibits the adsorptive potential of hydroxyapatite coated activated carbon (C-HAP) composite for the removal of Pb(II) from aqueous solution. The composite was prepared by co-precipitating CaCl2 and activated carbon mixture with (NH4)2HPO4 solution. The adsorbent was characterized by Scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD), and gas sorption analyzer. The effects of several factors, such as pH, initial concentration, adsorbent dose, contact time, and co-existing ions on the degree of adsorption performance were discussed in batch experiments. The adsorption process of Pb(Ⅱ) on C-HAP followed the pseudo-second order kinetic model, and the equilibrium data at different temperatures were best fitted to Langmuir isotherm model. The mechanism of Pb (II) removal by C-HAP was a complex physicochemical process, and the maximum adsorption capacity of was 416.67 mg/g, which was significantly higher than that of many other adsorbents. The thermodynamic calculations suggested that the Pb(II) adsorption process was spontaneous and exothermic in nature. According to this study, the composite of C-HAP with high adsorption capacity could be explored as a newly developed adsorbent for future column application in Pb(II) removal.