Lead cations immobilization by hydroxyapatite with cotton-like morphology

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 7.5.75