Natural hydroxyapatite powder from pig-bone waste (pHAP) for the rapid adsorption of heavy metals (Cu) in aqueous solution

Copper ions are prevalent in the natural environment and possess toxicity as heavy metal ions. The removal of Cu²⁺ from aqueous solutions can be achieved through adsorption, which is considered a straightforward method. In this study, we employed a facile approach to synthesize pig-bone hydroxyapatite material (pHAP), and the synthesized materials were subjected to characterization using XRD, SEM, FTIR, and BET techniques. The results showed that pHAP has a pure HAP structure, and the surface of HAP has a certain porosity, which provides good conditions for the adsorption of copper ions. Batch adsorption equilibrium experiments were conducted to investigate the various influencing factors, adsorption kinetics, and isotherms. The findings revealed that the optimal adsorption condition of Cu²⁺ (50 mg/L) on pHAP was pH 7, 318.15 K, the maximum adsorption capacity was 50.25 mg/g, and the adsorption capacity was superior to some adsorbents of the same type. Moreover, it can retain 74.15% of its reusability after being reused 5 times. The adsorption mechanism primarily involves monolayer adsorption through chemical processes, particularly ion exchange, coprecipitation, and complexation reactions. Therefore, pHAP has industrial application potential in the field of copper ion adsorption.