Fabrication of dopamine/TiO2 nanocomposite hydrogel using fenugreek gum for efficient photocatalytic degradation of organic pollutants under visible light irradiation

Abstract

The efficient removal of organic pollutants from wastewater is a global challenge and poses a significant threat to public health and ecosystems. In this study, we synthesized a novel fenugreek gum-based polymer functionalized with dopamine (DA) and monomers dimethylamino ethyl methacrylate (DMA), acrylamide, and N, N, methylene bis acrylamide (MBA) as a crosslinker and TiO₂ nanocomposite hydrogel photocatalytic degradation for environmental remediation. The nanocomposite hydrogel was determined using various analytical techniques such as FT-IR, XRD, FESEM, EDX, DRS-UV, TEM, LC-MS, and XPS. The optical band gap was at 2.81 eV, calculated from UV–visible DRS spectra. The XRD confirmed the crystalline and anatase phases. TEM, EDX, and XPS analyses defined the size, shape, chemical composition, and purity of synthesized FNG/DDM/TiO₂ nanocomposite hydrogel. The resulting nanocomposite hydrogel photocatalyst effectively degraded hazardous pollutants such as methylene blue (MB) and Congo red (CR) organic dyes under visible light irradiation. The decomposition efficiency of Congo red is 95.27 % within 75 min and methylene blue is 73.26 % within 150 min. Moreover, the results of the trapping experiment revealed that the active species in the photocatalytic degradation process are holes (h⁺) and super oxide radicals (^.O₂^-), more reactive species. The probable degradation intermediates and the degradation pathway were analyzed by LCMS analysis, and the degradation fragments formed during Congo red (CR) dye degradation were identified. The recyclability and stability were studied in the presence of a photocatalyst, achieving 90.5 % degradation after four cycles. The FNG/DDM/TiO₂ hydrogel also effectively removed dyes from wastewater containing organic pollutants. The novel FNG/DDM/TiO₂ nanocomposite hydrogel, synthesized through an environmentally friendly polymer, demonstrated high efficiency in degrading organic dyes, excellent recyclability with robust structural stability, and significant potential for photocatalytic degradation of wastewater across various industries.