nano-hydroxyapatite, adsorption capacity, manganese, wastewater treatment
A novel Hydroxyapatite nanopowder prepared from a biogenic waste, shell of a gastropod, by hydrothermal method was used for adsorption of manganese ion in wastewater. The nano-Hap produced was characterized using XRD, FTIR and SEM. The surface area of the nanopowder was determined using BET. The effects of contact time, pH, initial ion concentration, adsorbent dosage and adsorbent calcining temperature on the manganese adsorption were investigated. Increasing initial ion concentration increases removal efficiency; as pH increases, removal efficiency increases. However, as adsorbent calcining temperature increases, removal efficiency decreases. 79 % removal efficiency of manganese was obtained at 200 ppm initial ion concentrations, pH 3 and 120 OC adsorbent calcining temperature. The equilibrium removal process of manganese ions by the nano-HAp was described well with the Langmuir isotherm model, resulting in the maximum adsorption capacity of 3.163 mg/g manganese ions on nanoHAp. The results of the thermodynamic and kinetic investigations indicated that the adsorption reactions were spontaneous (ΔG◦ < 0), endothermic (ΔH◦ > 0) and pseudo second order model fitted better the adsorption kinetics of manganese on the nanoHAp. The main mechanism for manganese ions removal using the nanoHAp was suggested to be a complex compound formation on nanoHAp surface.