Investigation of effective parameters on thorium adsorption by nanohybrid adsorbent of polyvinyl alcohol/ titanium oxide functionalized with amine groups

In this study, an adsorbent material of poly vinyl alcohol (PVA)/ titanium oxide (TiO2)/ amino-propyltriethoxysilane (APTES) was synthesized by the casting method. The FTIR spectra indicated that PVA/TiO2/APTES nanohybrid adsorbent was functionalized by amine groups. The SEM analysis also showed that the TiO2 nanoparticles were dispersed well on the adsorbent surface. Several influential variables such as TiO2 content, APTES content, pH, contact time, initial concentration and temperature were studied in a sorption batch mode. The optimum  conditions for thorium were specified in 20%W of TiO2, 10%W of APTES, within the contact time of 5 hours, adsorbent dose of 1 g/L, temperature of 45°C and pH of 5. The kinetic data were fitted to pseudo-first-order, pseudo-second-order and double-exponential models. Based on the results, the double-exponential model described the experimental data well. Three isotherm models, namely Freundlich, Langmuir and Dubbinin-Radushkevich were used for analysis of the equilibrium data. Based on the results, the Freundlich isotherm was better than other isotherms. The maximum adsorption capacity of the nanohybrid for thorium was 43.7 mg/g. Calculation of thermodynamic parameters showed that the nature of thorium sorption onto the nanohybrid was endothermic and spontaneous. The change of adsorption capacity after five sorption- desorption cycles was less than 20%.