Photocatalytic degradation of naphthol blue from Batik wastewater using functionalized TiO2-based composites.

This work provides a first-time comparative study examining the photocatalytic activity of functionalized TiO2-based composites to eliminate naphthol blue in Batik wastewater. Reduced graphene oxide (RGO) was synthesized by oxidizing solid graphite using the Hummers' method followed by sonication and reduction. N-doped TiO2 (N-TiO2) was synthesized from titanium tetrachloride (TiCl4) and urea (CH4N2O) precursors by the sol-gel method. N-TiO2 modified RGO (RGO/NT) was synthesized using a hydrothermal method from N-TiO2 and RGO. Prepared TiO2-based composites and commercial TiO2, for comparison were characterized using Fourier transform infrared spectrometer (FTIR), X-Ray diffractometer (XRD), scanning electron microscope-energy dispersive X-ray (SEM-EDX), and UV-Vis diffuse reflectance spectrometer (UV-Vis DRS). FTIR characterization indicated Ti-N bonding in N-TiO2 and RGO/NT. XRD patterns showed that commercial TiO2 had a rutile phase, while N-TiO2 and RGO/NT had an anatase phase with crystal sizes of 30.09, 16.28, and 12.02 nm, respectively. SEM results displayed the presence of small and glossy white N-TiO2 dispersed on the surface of RGO. Characterization using UV-Vis DRS showed that the band gap energy values for TiO2, N-TiO2, and RGO/NT were 3.25, 3.12, and 3.08 eV with absorption regions at the wavelengths of 382, 398, and 403 nm, respectively. The highest photocatalytic activity for RGO/NT for degrading naphthol blue was obtained at pH 5, with a photocatalyst mass of 60 mg, and an irradiation of 15 min. Photocatalytic degradation by RGO/NT on Batik wastewater under visible light showed higher effectivity than under UV light.

Simultaneous photocatalytic removal of organic dye and heavy metal from textile wastewater over N-doped TiO2 on reduced graphene oxide.

Methylene blue (MB) and hexavalent chromium(Cr(VI)) are hazardous pollutants in textile waste and cannot be completely removed using conventional methods. So far, there have been no specific studies examining the synthesis and activity of N-TiO2/rGO as a photocatalyst for removing MB and Cr(VI) from textile wastewater. This work especially highlights the synthesis of N-TiO2/rGO as a photocatalyst which exhibits a wider range of light absorption and is highly effective for simultaneous removal of MB-Cr(VI) under visible light. Titanium tetrachloride (TiCl4) was used as the precursor for N-TiO2 synthesis using the sol-gel method. Graphite was oxidized using Hummer's method and reduced with hydrazine to produce rGO. N-TiO2/rGO was synthesized using a hydrothermal process and then analyzed using several characterization instruments. The X-ray diffraction pattern (XRD) showed that the anatase N-TiO2/rGO phase was detected at the diffraction peak of 2θ = 25.61. Scanning electron microscopy and transmission electron microscopy (SEM-EDS and TEM) dispersive X-ray spectrometry images show that N-TiO2 particles adhere to the surface of rGO with uniform size and N and Ti elements are present in the N-TiO2/rGO combined investigated. Gas absorption analysis data (GSA) shows that N-TiO2/rGO had a surface area of 77.449 m2/g, a pore volume of 0.335 cc/g, and a pore size of 8.655 nm. The thermogravimetric differential thermal analysis (TG-DTA) curve showed the anatase phase at 500-780 °C with a weight loss of 0.85%. The N-TiO2/rGO composite showed a good photocatalyst application. The photocatalytic activity of N-TiO2/rGO for textile wastewater treatment under visible light showed higher effectiveness than ultraviolet light, with 97.92% for MB and 97.48% for Cr(VI). Combining N-TiO2 with rGO is proven to increase the light coverage in the visible light region. Removal of MB and Cr(VI) can be carried out simultaneously and results in a removal efficiency of 95.96%.