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

This work provides a first-time comparative study examining the photocatalytic activity of functionalized TiO-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 TiO (N-TiO) was synthesized from titanium tetrachloride (TiCl) and urea (CH₄N₂O) precursors by the sol-gel method. N-TiO modified RGO (RGO/NT) was synthesized using a hydrothermal method from N-TiO and RGO. Prepared TiO-based composites and commercial TiO, 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-TiO and RGO/NT. XRD patterns showed that commercial TiO had a rutile phase, while N-TiO 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-TiO dispersed on the surface of RGO. Characterization using UV-Vis DRS showed that the band gap energy values for TiO, N-TiO, 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.