Adsorption of copper ion from aqueous solutions by well-crystalized nanosized hydroxyapatite

Hydroxyapatite (HAp), the main mineral content of bones and teeth, is one of the most important calcium phosphate-based bio-ceramics. Due to its crystal structure, it has the potential to be used as a low cost and biocompatible adsorbent. In this study, nano-synthesized and well-crystallized HAp was used in adsorption process of copper which causes growth problems. In order to investigate the synthesized nano-HAp crystal structure and functional groups, x-ray diffraction pattern (XRD), Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy analyzes were performed. Nano-HAp concentration, copper concentration and time were selected as variables affecting copper adsorption and Box-Behnken design was applied. According to the results, it was found that at least 33 min and 510 mg l^-1 nano-HAp concentration was required to achieve a higher removal rate than 90% removal efficiency. It was determined that all selected independent variables are effective in copper removal. The optimization study was carried out with the findings obtained from the study and 514.0 mg l^-1 nano-HAp and 60.4 min were found to be required for optimal removal. Moreover, the lowest selected Cu concentration can be totally removed by 700 mg l^-1 nano-HAp and in 60.4 min of reaction time. This study demonstrates that nano-HAp can be used as an environmentally friendly adsorbent for copper removal from aqueous solution.