Ultrasound-assisted sol-gel synthesis and characterization of highly efficient OTES-Functionalized ZnO/GO nanocomposite for a novel purification of phosphoric acid using sonophotocatalytic process: Box-Behnken Design optimization

Octyltriethoxysilane-Functionalized Zinc Oxide/Graphene Oxide nanocomposites (OTES@ZnO/GO NCs) were synthesized via the ultrasound-assisted sol-gel synthesis technique. The surfaces of the ZnO/GO NCs were modified by grafting the organosilane agent, octyltriethoxysilane. The structure, morphology and elemental compositions of the samples were characterized using XRD, FESEM, TEM and EDX. The surface charge and specific surface area of samples were measured using Zeta potential and BET analysis, respectively. The various chemical functional groups and, absorption spectroscopy were performed using FTIR and RS spectrum, and UVVis spectrophotometer, respectively. Photoluminescence (PL) measurements have been used to investigate the fate of electron-hole and the performance of charge carriers trapping. Patterns of XRD showed a good agreement with the hexagonal structure and the crystalline size of ZnO NPs and OTES@ZnO/GO NCs were obtained as 21 and 16 nm, respectively. Response Surface Methodology (RSM) based on Box-Behnken Design (BBD) was applied to optimize the phosphoric extraction. The optimal conditions were found in 21.04 % of HCl concentration, a reaction time of 5 min and 6 of liquid-to-solid ratio to achieve 96.87% extraction efficiency. Based on the FTIR spectrum, the combination of UV/US irradiation in the degradation process resulted in the efficient removal of Ca2+ ions in 120 min.