Sulfur-doped TiO₂ (S-TiO₂) composites with reduced graphene oxide (rGO), wt. % of rGO equal to 0.5%, 2.75%, and 5.0%, were prepared by a one-pot solvothermal procedure. The aim was to improve photocatalytic performance in comparison to TiO₂ under simulated solar irradiation for the treatment of diclofenac (DCF) in aqueous medium. The obtained composites were characterized for physical-chemical properties using thermogravimetric analysis (TGA), X-ray diffractograms (XRD), Raman, scanning electron microscopy (SEM)/energy dispersive X-ray (EDX), Brauner Emmett Teller (BET), and photoluminescence (PL) analyses, indicating successful sulfur doping and inclusion of rGO. Sulfur doping and rGO have successfully led to a decrease in photogenerated charge recombination. However, both antagonistic and synergistic effects toward DCF treatment were observed, with the latter being brought forward by higher wt.% rGO. The composite with 5.0 wt.% rGO has shown the highest DCF conversion at pH 4 compared to that obtained by pristine TiO₂, despite lower DCF adsorption during the initial dark period. The expected positive effects of both sulfur doping and rGO on charge recombination were found to be limited because of the subpar interphase contact with the composite and incomplete reduction of the GO precursor. Consequent unfavorable interactions between rGO and DCF negatively influenced the activity of the studied S-TiO₂/rGO photocatalyst under simulated solar irradiation.

This study focused on developing and evaluating a continuous flow photoreactor with an immobilized photocatalyst. The titanium dioxide powder was deposited on glass beads and packed into sequentially connected columns surrounded by LED lamps. The volume of the reactor without beads is 2.4 L, and with beads, 0.8 L. The photocatalytic efficiency of the reactor was evaluated by observing the degradation of Plasmocorinth B pollutant and selected pharmaceuticals (ibuprofen, sulfamethoxazole and diclofenac) at different flow rates under illumination of varying number of lights in deionized water and ISO medium. CFD simulations were performed to analyze the velocity and radiation field. The relationship between mass transfer and reaction kinetics was quantitatively evaluated by calculating the Peclet number, Damköhler number, and mass transfer coefficients. Total organic carbon (TOC) was also measured in the resulting solutions to determine the rate of mineralization. The toxicity tests were performed by exposing the solutions to the planktonic crustacean Daphnia magna for 48 h. The results showed that the number of lights directly and the flow rate inversely affected the degradation of the parent compound. At lower flow rates, total degradation of 87-97 % of the contaminants was observed in one flow and halving the light intensity resulted in a 10-15 % decrease in overall degradation. The toxicity tests showed that toxic transformation products were formed and were present until the complete degradation of the parent compound, after which they were also degraded. This study shows that the continuous flow photoreactor presents a potential solution for large-scale wastewater treatment.

This study explores the influence of flow velocity, sphere size, and inter-sphere distance on hydrodynamics and mass transfer in a photocatalytic reactor. The effects of two different light configurations on light distribution and degradation were also evaluated. A 2D computational fluid dynamics (CFD) model was developed to simulate the continuous flow photocatalytic reactor with TiO₂-coated spheres and validated with experimental measurements by observing the degradation of methyl orange. The experimental setup consists of a tube containing an equal number of TiO₂-coated glass spheres. The case with radiation from one wall shows a non-uniform light distribution compared with the case with radiation from both walls. The CFD simulations focused on analyzing the velocity streamlines and turbulence characteristics (turbulent kinetic energy (TKE) and turbulence dissipation rate (TDR)). These parameters showed significant variations in each studied case. The case with larger spheres reached the highest velocity of 38 m/s of the pollutant solution. The highest TKE and TDR values of 0.47 m²/s² and 12.2 m²/s², respectively, were also observed in the same case, indicating enhanced mixing and mass transfer to the catalyst surfaces, ultimately leading to a more efficient degradation process. The results show that an optimized design of photocatalytic reactors can significantly improve mass transfer and, thus, degradation efficiency.

A green method for depositing a CuO layer with good adhesion and a large surface area on a support of activated alumina (Al₂O₃) was evaluated. The relatively simple method consists of adsorption of a copper salt on the surface of Al₂O₃, formation of Cu(OH)₂, and subsequent decomposition of the hydroxide to CuO. The XRD confirmed that the deposited photocatalyst crystalized at low temperatures (80 °C). Furthermore, BET measurements show a surface area of about 90 m²/g. The large surface area is the result of the speed of the conversion and decomposition reactions. The photokilling properties of the prepared photocatalyst were evaluated using E. coli cells and the leaching of copper ions was determined using ICP-MS. The photocatalytic efficiency was also evaluated by the degradation of an organic azo dye. The prepared photocatalyst shows good activity in the purification and disinfection of treated water. The described method is economical, fast, and can be considered green, since the only byproducts are water and NaCl.

Hydrothermal reactions represent a simple and efficient method for the preparation of nanostructured TiO₂ particles that could be of interest as photocatalysts or catalytic supports. Although the particle size is in the range of 2–5 µm, the nanostructures composing the particles ensure a large specific surface area with values above 100 m²/g. The effects of the different synthesis parameters on the morphology, photocatalytic activity, and stability of the prepared material were studied. The surface morphology of the prepared TiO₂ powders was studied by scanning electron microscopy (SEM). To further characterize the samples, the specific surface area for different morphologies was measured and the photocatalytic activity of the prepared powders was tested by degrading model pollutants under UV irradiation. The results show that the initial morphology had little effect on the photocatalytic properties. On the other hand, the final calcination temperature significantly increased the degradation rates, making it comparable to that of P25 TiO₂ (particle size 20–30 nm).