Chitosan-Zinc Oxide Nanocomposite as Nanoadsorbent for The Removal of Toxic Metal Ions from Aqueous Solutions
Keywords:Chitosan-zinc oxide nanocomposite, Nanoadsorbent, Water treatment, Heavy metals, Adsorption mechanism
AbstractAs estimated by World Health Organization (WHO), in 2017 there were 2.1 billion people who did not have safely managed water, while 844 million did not even have a basic drinking water service. Water treatment technologies are of important in this context. In this study, we have prepared, characterised and evaluated the potential of chitosan-zinc oxide (Cs-ZnO) nanocomposite to adsorb Cd(II), Cu(II), Ni(II) and Pb(II) ions from aqueous solutions. The Cs-ZnO nanocomposite was prepared using co-precipitation method. The physico-chemical properties of the nanocomposites were studied using fourier transform infrared (FTIR) spectrometer, x-ray diffraction (XRD) spectrometer, thermogravimetric analyser (TGA), differential scanning calorimeter (DSC), field emission scanning electron microscope (FESEM) and energy dispersive x-ray (EDX) spectrometer. The effects of solution pH, adsorbent dosage, initial concentration and contact time on adsorption behaviour of metal ions onto Cs-ZnO nanocomposite were examined. The adsorption equilibrium data of metal ions were correlated to the Langmuir and Freundlich isotherm models, while the adsorption kinetic data were fitted to the pseudo-first and pseudo-second order kinetic models. The separation factor (RL) and Freundlich constant (n) values suggest that the adsorption process was favourable. The maximum adsorption capacity (Qmax) of Cd(II), Cu(II), Ni(II) and Pb(II) ions onto Cs-ZnO nanocomposite was 114.94, 129.87, 121.95 and 192.30 mg/g, respectively. The adsorption efficiency of Cs-ZnO nanocomposite was comparable to that of two commercial adsorbents used to treat water in Iraq and Indonesia, namely date seeds and bamboo derived activated carbons.