Hydrogel nanocomposite based on chitosan-g-acrylic acid and modified nanosilica with high adsorption capacity for heavy metal ion removal

In this study, a novel hybrid hydrogel based on chitosan, acrylic acid and amine-functionalized nanosilica was prepared and characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. This hydrogel nanocomposite was used for removal of Co 2+ , Cu 2+ , Pb 2+ and Zn 2+ ions from aqueous solution. The metal ion adsorption was measured by inductively coupled plasma mass spectrometry. The adsorption behavior showed that the presence of modified nanosilica enhanced the porosity of the hydrogel network and affected its adsorption capacity in response to different parameters such as nanosilica content, metal ion concentration, adsorbent content, pH value and contact time. The morphology study showed that the nanosilica which was functionalized by 3-aminopropyl triethoxysilane increased the porosity of the hydrogel and created extensive network domains which can permeate water. The nanosilica may act as a physical cross-linker. The adsorption behavior of nanocomposite hydrogel showed that its high porous structure and the presence of amine functional groups on the nanosilica surface enhanced its adsorption capacity. On the other hand, the nanocomposite did not show any selectivity for removal of Co 2+ , Cu 2+ , Pb 2+ and Zn 2+ ions from aqueous solution due to the specific interaction between nanocomposite and these metal ions.