Adsorption of Cd (II) and Zn (II) from aqueous solutions using magnetic hydroxyapatite nanoparticles as adsorbents

Magnetic hydroxyapatite nanoparticles (MNHAP) adsorbents were synthesized and were used for the removal of Cd2+ and Zn2+ from aqueous solutions. The properties of this magnetic adsorbent were characterized by scanning electron microscopy (SEM), energy dispersive analysis system of X-ray (EDAX), X-ray powder diffraction (XRD) analysis, zeta potential, BET surface area measurements and magnetization curves. Experiments were carried out to investigate the influence of different sorption parameters, such as contact time, initial concentration of metal ions, the dosage of MNHAP, pH value of the solutions and competitive adsorption behavior. Kinetic data are well fitted by a pseudo second-order model and the equilibrium data are analyzed by Langmuir model very well with high correlation coefficient. From the Langmuir isotherms, the maximum adsorption capacities of MNHAP adsorbents towards Cd2+ and Zn2+ are 1.964 and 2.151 mmol g−1, respectively. The results revealed that the most prominent advantage of the prepared MNHAP adsorbents consisted in their separation convenience compared to the other adsorbents.