Chitosan–collagen/hydroxyapatite and tripolyphosphate nanocomposite: characterization and application for copper removal from aqueous solution

In this study, collagen (Col) and hydroxyapatite (HAp) nanoparticles synthesized from fishery wastes were used to fabricate chitosan–collagen (CTS–Col) and chitosan–collagen/hydroxyapatite (CTS–Col/HAp) nanocomposite materials that were cross-linked with tripolyphosphate (TPP). The resulting composite was discovered to be an effective adsorbent capable of removing Cu(II) ions from aqueous solutions. FTIR and SEM techniques were used to investigate the functional groups and morphology of nanocomposite. Both adsorbents have a microporous structure, and the amino and phosphate groups are assumed to be the major functional groups involved in the sorption of Cu(II) ions. At 50 °C and pH 5.5, the results demonstrated that Cu(II) ion adsorption on CTS–Col and CTS–Col/HAp surfaces followed a pseudo-second-order kinetic model and that the Langmuir isotherm was obeyed at equilibrium, with a maximum adsorption capacity of 166 and 170 mg/g for CTS–Col and CTS–Col/HAp, respectively. The mechanism by which the Cu(II) ion adsorbs onto the nanocomposite surface was attributed to electrostatic interaction. Negative ∆G ° and positive ∆H ° values established that adsorption was an endothermic and spontaneous process, respectively. CTS–Col and CTS–Col/HAp were reusable after three adsorption–desorption cycles, with a removal percentage decrease of 21.7% and 7.6%, respectively.