Lead cations immobilization by hydroxyapatite with cotton-like morphology

Hydroxyapatite (HAP) in cotton morphology was first prepared by co-precipitation method using cotton as templates. The effect of contact time, initial concentration, and temperature on HAP immobilization of Pb2+ ions was studied using a batch technique. It was remarked that the maximum amount of Pb2+ immobilization by HAP was 1690.2 mg/g with a minimum contact time of 50 min. The pseudo-second-order kinetic model has been proposed to fit the data. Thermodynamic parameters such as ΔG0, ΔH0, and ΔS0 were calculated to understand the nature of sorption. Original HAP and immobilization products were characterized using SEM, TEM/EDAX, XRD and BET. In the presence of Cl−, the dissolution of HAP followed by precipitation of chloropyromorphite was found to be the main operating mechanism for Pb2+ immobilization by HAP. The mechanisms of cotton templated HAP removal the Pb2+ was varied depending on the pH of aqueous solution. At low pH 2.5, the maximum adsorption capacity of the prepared HAP for Pb2+was up to 1690.2 mg/g much higher than other reported HAP materials, the mechanism of dissolution/precipitation was the dominated one. The mechanism of ion exchange was dominated at pH 4.5–6.5, two mechanisms competed at 3.5, and hydroxyl complex was formed at pH higher than 7.5. [Display omitted] •Hydroxyapatite (HAP) in cotton morphology was prepared using cotton as templates.•The maximum adsorption capacity of the prepared HAP for Pb2+was up to 1690.2 mg/g.•Dissolution/precipitation was the main mechanism for Pb2+ immobilization.•HAP and immobilization products were characterized with SEM, TEM/EDAX, XRD and BET.