A new porous composite hydroxyapatite/chitosan/microcrystalline-cellulose: synthesis, characterization and application to the adsorption of Eriochrome Black T

In the current study, a porous composite material, hydroxyapatite/chitosan/microcrystalline-cellulose (CaHAp–CS–MCC), was successfully prepared and used for the adsorption of Eriochrome Black T (EBT) from water. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential thermal analysis (DTA), thermogravimetric analysis (TGA), specific surface area (SSA), and atomic force microscope (AFM) were used to evaluate the physicochemical properties of the prepared adsorbents. CaHAp–CS–MCC exhibited a decrease in crystallinity and reduction in crystallite size. CaHAp–CS–MCC surface exhibited cracks and pores. AFM displayed changes in surface micro-texture of CaHAp, formation of new surface structures, and variations in particle size and distribution. Upon grafting CaHAp with CS and MCC, its specific surface area decreased from 139.224 to 11.775 m²/g. BET suggested that filling CaHAp pores by CS and MCC contributed to the reduction in surface area. The pore volume values decreased from 2.56 × 10^–1 (CaHAp) to 3.91 × 10^–2 cm³/g (CaHAp–CS–MCC). Adsorption equilibrium was reached at about 40 min. The adsorption capacities values of CaHAp–CS–MCC and CaHAp were equal to 248 mg/g and 92 mg/g, respectively. The pseudo-second order and the Langmuir equations fitted well the adsorption phenomenon. The calculated thermodynamic parameters showed an exothermic and non-spontaneous system.