Synthesis, characterization of Ag-WO3/bentonite nanocomposites and their application in photocatalytic degradation of humic acid in water.

Abstract

In this study, Ag-WO3/bentonite nanocomposites were synthesized through a sol-gel process, a microwave irradiation technique, and a sol-immobilization process to examine their impact on the photocatalytic activity in the degradation of humic acids. The optical and structural properties of the synthesized materials were characterized using X-ray diffraction (XRD), Fourier-transform-infrared spectra (FTIR), field emission scanning electron microscope (FE-SEM) with energy dispersive X-ray (EDX), UV-Vis diffused reflectance spectra (UV-Vis DRS), Brunauer-Emmett-Teller (BET) method, and transmission electron microscope (TEM). The presence of Ag and WO3 peaks in the XRD and EDX spectra confirmed the synthesis of Ag-WO3 nanoparticles in the composite. The monoclinic structure of the produced WO3 samples are shown by powder X-ray diffraction patterns. The WO3-based nanocomposites' photocatalytic activity was improved by the composition of Ag and bentonite, which reduced the optical bandgap energy of WO3. The binary (Ag-WO3) nanocomposite showed improved photocatalytic activity towards the degradation of humic acid (HA) from 58% (pristine WO3) to 82% (Ag-WO3) when compared with the pristine WO3 sample under the visible light irradiation. Notably, the ternary (Ag-WO3/bent) nanocomposite demonstrated an outstanding photocatalytic efficiency of HA degradation (91.0%) under normal conditions (pH = 7.0 and 25°C). Humic acid degradation in Ag-WO3/bent was expressed by the pseudo-first-order kinetic. To summarize, integrating Ag, WO3, bentonite, and visible light radiation to activate HA efficiently can be offered as a successful and promising technique for wastewater treatment.