Novel Fe3O4/hydroxyapatite/β-cyclodextrin nanocomposite adsorbent: Synthesis and application in heavy metal removal from aqueous solution

The increased global concern on environmental protection has made researchers focus their attention on new and more efficient methods of pollutant removal. In this research, novel nanocomposite adsorbents,i.e., magnetic hydroxyapatite (Fe3O4@HA) and magnetic hydroxyapatite beta-cyclodextrin (Fe3O4@HA-CD) were synthesized and used for heavy metal removal. The adsorbents were characterized by FTIR, XRD, TGA, VSM, and SEM. In order to investigate the effect of beta-cyclodextrin (beta-CD) removal efficiency, adsorption results of nine metal ions were compared for both adsorbents. beta-CD showed the most increasing effect for Cd2+ and Cu2+ removal, so these two ions were selected for further studies. The effect of diverse parameters including pH, contact time, initial metal ion concentration and adsorbent dosage on the adsorption process was discussed. The optimum pH was 6 and adsorption equilibrium was achieved after 1 hr. Adsorption kinetic data were well fitted by pseudo-second-order model proposing that metal ions were adsorbed via chemical reaction. Adsorption isotherm was best described by the Langmuir model, and maximum adsorption capacity for Cd2+ and Cu2+ was 100.00 and 66.66 (mg/g), respectively. Desorption experiment was also done, and the most efficient eluent used for desorption of metal ions was EDTA (0.001 M) with 91% and 88% of Cd2+ and Cu2+ release, respectively. Recyclability studies also showed a 19% decrease in the adsorption capacity of the adsorbent after five cycles of regeneration. Therefore, the synthesized adsorbents were recognized as potential candidates for heavy metal adsorption applications.