Simultaneous removal of copper and zinc ions by Chitosan/Hydroxyapatite/nano-Magnetite composite

Abstract

In this study, we assessed the simultaneous removal of Cu(II) and Zn(II) from aqueous solutions, using Chitosan/Hydroxyapatite/nano-Magnetite (Fe3O4) composite as an efficient adsorbent. Chitosan and HAP are low cost and accessible material, extracted from shrimp shell and bone ash, respectively. The magnetite nano-particles were synthesized and then used for the quick and easy separation of the adsorbent from the solution using an external magnet. The newly synthesized adsorbent was characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDAX), Brunauer–Emmett–Teller (BET) and transmission electron microscopy (TEM). The evaluation of metal ions concentration within the samples was determined by flame atomic absorption spectroscopy (FAAS). Several isotherm models such as Freundlich, Tempkin and Langmuir models have been used for mechanistic studies. The results showed that the adsorption data were well fitted with Langmuir isotherm for Zn2+ (R2 = 0.987) and Tempkin isotherm for Cu2+ (R2 = 0.987). Four Conventional kinetic models were applied, and the results indicated that the pseudo-second-order model has convenient fitting with the adsorption data for both ions (Zn2+ and Cu2+). Thermodynamic parameters were evaluated to obtain the nature of the adsorption process onto the composite and revealed that the adsorption process was physical and spontaneous. By using central composite design (CCD) with response surface methodology (RSM), the percentage level of ion removal was investigated with respect to several parameters such as the contact time, initial concentrations of Cu (II), concentration of Zn (II), pH, and adsorbent dosage. The optimized value for these parameters were 65 min, 2.87 mg L−1, 2.61 mg L−1, 5.5, and 0.018 g, respectively.