Investigation of the usability of hydroxyapatite adsorbents synthesized from fish bone and egg shell wastes in the removal of Cu(II) ions from their aqueous solution

Abstract

In this study, hydroxyapatites (FSHAp and ESHAp) from natural waste materials (fish bones and egg shells) were successfully synthesized and their physicochemical properties were characterized. Cu(II) ion adsorption potentials of FSHAp and ESHAp particles under different experimental conditions (pH, different adsorbent and Cu(II) concentration, contact time and temperature) were optimized by using the Response Surface Methodology (RSM), and their Cu(II) adsorption capacities were compared. The surface morphology, crystal structure, elemental contents, surface area and pore ratios of produced hydroxyapatite-based adsorbents were determined by using FTIR, SEM-EDX, XRD characterization techniques. Isotherm and kinetic models were calculated to determine their adsorption mechanism, and the results showed that the Cu(II) adsorption process of FSHAp and ESHAp particles was more suitable for the Tempkin and Scarthard isotherm models and the pseudo-second order kinetic model. The optimum adsorption capacity for Cu(II) removal for FSHAp and ESHAp particles were obtained as 19.4 mg/g and 10.6 mg/g, respectively (pH 5.5, 90 mg Cu(II)/L, 2g/L adsorbent concentration, 25℃ and 25 min). Desorption and regeneration studies have shown that adsorbents can be used effectively for up to three consecutive cycles. The results of this study revealed that FSHAp and ESHAp particles can be used as alternative, environmentally friendly, low-cost adsorbents for Cu(II) removal from aqueous environments and environmental improvements in the perspective of zero waste approach.