Influence of anatase and rutile phase in TiO2 upon the photocatalytic degradation of methylene blue under solar irradiation in presence of activated carbon

Photocatalytic activity of ZrO2/TiO2/Fe3O4 ternary nanocomposite for the degradation of naproxen: characterization and optimization using response surface methodology

In this study, ZrO₂, TiO₂, and Fe₃O₄ components were synthesized by co-precipitation, sol–gel, and co-precipitation methods, respectively. In addition, solid-state dispersion method was used for synthesizing of ZrO₂/TiO₂/Fe₃O₄ ternary nanocomposite. The ZrO₂/TiO₂/Fe₃O₄ nanocomposite was characterized by different techniques including XRD, EDX, SEM, BET, FTIR, XPS, EELS, and Photoluminescence (PL). The FTIR analysis of ZrO₂/TiO₂/Fe₃O₄ photocatalyst showed strong peaks in the range of 450 to 700 cm⁻¹, which represent stretching vibrations of Zr–O, Ti–O, and Fe–O. The results of FTIR and XRD, XPS analyses and PL spectra confirmed that the solid-state dispersion method produced ZrO₂/TiO₂/Fe₃O₄ nanocomposites. The EELS analysis confirmed the pure samples of Fe₃O₄, TiO₂ and ZrO₂. The EDAX analysis showed that the Zr:Ti:Fe atomic ratio was 0.42:2.08:1.00. The specific surface area, pores volume and average pores size of the photocatalyst were obtained 280 m²/g, 0.92 cm³/g, and 42 nm respectively. Furthermore, the performance of ZrO₂/TiO₂/Fe₃O₄ nanocomposite was evaluated for naproxen removal using the response surface method (RSM). The four parameters such as NPX concentration, time, pH and catalyst concentration was investigated. The point of zero charge of the photocatalyst was 6. The maximum and minimum degradation of naproxen using photocatalyst were 100% (under conditions: NPX concentration = 10 mg/L, time = 90 min, pH = 3 and catalyst concentration = 0.5 g/L) and 66.10% respectively. The stability experiment revealed that the ternary nanocatalyst demonstrates a relatively higher photocatalytic activity after 7 recycles.

Tio2/SiO2/Fe3O4 magnetic nanoparticles synthesis and application in methyl orange UV photocatalytic removal

Three main parameters affecting TiO₂/SiO₂/Fe₃O₄ nanoparticles activity in photocatalytic degradation of methyl orange were investigated using response surface methodology (SRM). Precipitation method and sol-gel technique were used to prepare SiO₂/Fe₃O₄ electromagnetic composite support and TiO₂/SiO₂/Fe₃O₄ photocatalytically active nanoparticles. The specific surface area, pore volume, and average pore size of the synthesized nanoparticles were respectively equal to 56 m²/g, 0.12 cm³/g and 9.4 nm. The point of zero charge (PZC) of the catalyst was measured to be 5.9. The maximum and minimum photocatalytic degradation of methyl orange using the synthesized nanoparticles were 100% and 30%, respectively. A linear model was fitted to the obtained results with R²_adjusted equal to 0.87. The results of analysis of variance (ANOVA) revealed that catalyst concentration, reaction media pH and aeration rate were significantly affected the photocatalytic activity. Optimization was performed considering photocatalytic activity as the main objective functions. In order to maximize photocatalytic activity, catalyst loading, reaction media pH and aeration rate were respectively adjusted to 2,000 ppm, 3 and 2.5 L/min, which resulted in total methyl orange removal. Considering promising photocatalytic activity of TiO₂/SiO₂/Fe₃O₄ along with core-sell nanocomposite separation performance led us to propose this photocatalyst as an alternative solution for treating waste waters.

C-doped anatase TiO2: Adsorption kinetics and photocatalytic degradation of methylene blue and phenol, and correlations with DFT estimations

This work shows an easy and eco-friendly methodology to obtain almost pristine anatase phase of TiO₂ by using furfural, a biomass-derived molecule, as a bio-template. The photocatalytic activity was studied following the degradation of methylene blue and phenol under artificial solar irradiation. Results were compared against those obtained on a commercial pristine anatase TiO₂. The pseudo first-order, the second-order and the intraparticle diffusion kinetic models were verified. The textural and surface chemistry properties of the materials were correlated with the surface density of molecules adsorbed in equilibrium. The reaction-rate showed an almost perfect quadratic regression as a function of the surface density. Theoretical estimations of the density of states by DFT + U were performed showing that the total electron charge in the oxygen bonded to anatase TiO₂ increased due to carbon doping in agreement with the prediction of appearance of atomic orbitals 2p from carbon atom in the hybrid material. C-doping is responsible of the red-shift from 3.14 to 2.94 eV observed for a Ti₁₅O₃₂C super-cell than pristine anatase Ti₁₆O_32. The increase in the activity of the C-doped TiO₂ photocatalyst was due to the decrease in the energy band-gap promoting a higher absorption of photons from the visible light.