Natural hydroxyapatite from fishbone waste for the rapid adsorption of heavy metals of aqueous effluent

In this paper, metal ions removal using hydroxyapatite (HAp) derived from fishbone waste was reported. Various characterization techniques confirmed the presence of HAp. Optimal adsorption occurred in the first 5 min of contact for both Ni²⁺ and Cu²⁺ ions. Larger particle size favor higher adsorption efficiency for Ni²⁺ case while the reverse was displayed for Cu²⁺ case. More than 80% ions removal was achieved in all cases for Ni²⁺, but for the case with Cu²⁺ ions, only particle size of 53μm achieved optimal ions removal of > 87%. In both cases, heat treatment was unnecessary. The samples after contact with Cu²⁺ required neutralization but no treatment was required for Ni²⁺ case. SEM results showed that higher ion removal efficiency was attributed to higher porosity. Further testing with atomic adsorption spectroscopy carried out with Ni²⁺, Cu²⁺ and Zn²⁺ showed the optimal particle size was 53μm and > 95% ion removal efficiency achieved with optimal setting for all cases. Cu²⁺ adsorption was fitted with Langmuir adsorption isotherm while Ni²⁺ and Zn²⁺ adsorption were fitted with Freundlich adsorption equation. Unchanged pH value of aqueous solution for Cu²⁺ case led to the conclusion that HAp performed best as a bioadsorbent at a more neutral pH. This study is expected to contribute to metal ions removal in water purification and wastewater treatment.