Amino-functionalization of PVA/TiO 2 -CeO 2 nanohybrid adsorbent for the removal of selenium ions from aqueous solutions: Equilibrium and kinetics studies

In this study, a hybrid nanoadsorbent (HnA), (PVA/TiO2-CeO2), was synthesized and amino-functionalized by 3-aminopropyltriethoxysilane (APTES) to produce AHnA, for use in an advanced selenium adsorption study focusing on nonlinear equilibrium and kinetics models. AHnA was characterized using XRD, FTIR spectroscopy, SEM, and EDX elemental analyses, as well as BET-BJH techniques. According to the FTIR results, APTES has successfully cross-linked the PVA chain and introduced amine groups on the surface. Moreover, the modification resulted in an increase in the total pore volume from 0.0061 cm3/g in HnA to 0.021 cm3/g in AHnA. Several adsorption experiments were conducted to determine the impact of varying contact times within a pH range of 1 to 8 and concentrations ranging from 5 to 200 mg/L, using a One-Variable-At-a-Time (OVAT) procedure. Accordingly, a dosage of 2 g/L of modified nanocomposite exhibits optimal performance for removing selenium from a 20 mg/L solution at an acidic pH of 3 during 300 minutes of contact with selenium ions, while conforming to a pseudo-second-order kinetic model. The assessment of various nonlinear isotherm models for analyzing equilibrium data revealed that the experimental data of selenium adsorption conformed to a generalized isotherm, showing a maximum monolayer adsorption capacity of 17.643 mg/g.