A Study of Adsorption Behaviour of Cu(II) on Hydroxyapatite-Coated-Limestone/Chitosan Composite

In this experiment, chitosan (CS), waste limestone and diammonium hydrogen phosphate were used as raw materials to synthesize HAp-coated-stone composites/CS by one-step blending method. Then, the prepared HAp-coated-stone composites/CS composite material was used to remove Cu (II) in the solution. The structure and microstructure of the composite were characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis, Scanning Electron Microscopy, Brunauer–Emmett–Teller and Thermogravimetric Analysis. The results showed that with the addition of CS, the overall thermal stability of the composite improved, while its specific surface area decreased. Moreover, the composite was a mesoporous material. HAp-coated-stone/CS composites with small amounts of CS (0.5%) can remarkably increase Cu (II) removal. The HAp-coated-limestone/CS-0.5% had better resistance to pH changes compared with HAp-coated-limestone. Under the initial concentration of 20 mg/L, the maximum adsorption capacity for Cu (II) adsorption by HAp-coated-limestone/CS-0.5% was about 130.75 mg/g at 40 °C. The equilibrium data and kinetic were well described by Freundlich models and pseudo-second-order, respectively. The possible mechanisms for Cu (II) adsorption onto HAp-coated-stone/CS composites surface have been proposed.