Synthesis and Characterization of N and Fe-Doped TiO2 Nanoparticles for 2,4-Dimethylaniline Mineralization

Photocatalytic degradation of naphthol blue from Batik waste 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 irradation of 15 min. Photocatalytic degradation by RGO/NT on Batik wastewater under visible light showed higher effectivity than under UV light.

Co, Cu, Fe, and Ni Deposited over TiO2 and Their Photocatalytic Activity in the Degradation of 2,4-Dichlorophenol and 2,4-Dichlorophenoxyacetic Acid

Pure TiO2 synthesized by the sol-gel method and subsequently deposited at 5% by weight with Co, Cu, Fe, and Ni ions by the deposition–precipitation method were studied as photocatalysts. The nanomaterials were analyzed by SEM, TEM, UV-Vis DRS, DRX, Physisorption N2, and XPS. The SEM and TEM images present a semi-spherical shape with small agglomerations of particles and average size between 63 and 65 nm. UV-Vis results show that a reduction below 3.2 eV exhibits a redshift displacement and increment in the optical absorption of the nanoparticles promoting the absorption in the UV-visible region. XRD spectra and analysis SAED suggest the characteristic anatase phase in TiO2 and deposited materials according to JCPDS 21-1272. The specific surface area was calculated and the nanomaterial Ni/TiO2 (21.3 m2 g−1) presents a slight increment when comparing to TiO2 (20.37 m2g−1). The information generated by the XPS spectra present the deposition of metallic ions on the support and the presence of different valence states for each photocatalyst. The photocatalytic activity was carried out in an aqueous solution with 80 mg L−1 of 2,4-D or 2,4-DCP under UV light (285 nm) with 100 mg L−1 of each photocatalysts for 360 min. The nanomaterial that presented the best efficiency was Ni/TiO2, obtaining a degradation of 85.6% and 90.3% for 2,4-D and 2,4-DCP, respectively. Similarly, this material was the one that presented the highest mineralization, 68.3% and 86.5% for 2,4-D and 2,4-DCP, respectively. Photocatalytic reactions correspond to the pseudo-first-order Langmuir–Hinshelwood model.