Synthesis of modified chitosan TiO2 and SiO2 hydrogel nanocomposites for cadmium removal

Abstract

Heavy metals removal from wastewaters and surface waters using low cost and eco-friendly adsorbents is one of the best ways to eliminate these impurities. In the current study, the nanocomposites based on chitosan-g-(acrylamide-co-itaconic acid) and titanium dioxide or silicon dioxide nanoparticles, were synthesized and their antibacterial property and the removal of Cd2+ from an aqueous solution have been investigated. The hydrogel and nanocomposites were synthesized via in situ polymerization within TiO2 and SiO2 nanoparticles separately. The products were characterized using FTIR, TGA, SEM, BET and EDX techniques. These analyses proved the synthesized nanocomposites and dispersion of nanoparticles with desirable properties. Nanocomposites were shown as porous structures with the average pore diameter of 4.40 and 5.05 nm for TiO2 and SiO2 composite, respectively. In addition, water absorption results indicated that by increasing the amount of nano particles, the water absorption decreases from 28 to 15 g/g for SiO2 nanocomposite and from 21 to 11 g/g for TiO2 nanocomposite. The effect of initial pH, initial concentration and time has been studied. Highest cadmium adsorption capacity for TiO2 and SiO2 nanocomposites respectively are 303, and 291 mg/gr. In addition, the equilibrium data and kinetics are described perfectly by pseudo second order kinetics and Freundlich isotherm. Freundlich isotherm has fitted the experimental data with the R2 of 0.96 and 0.91 for SiO2 and TiO2 nanocomposite, respectively. Antibacterial results showed that the synthesized nanocomposite inhibits the growth of E. coli and S. aureus.