Hierarchically structured TiO2-based composites for Fenton-type oxidation processes

Photocatalytic-Fenton Process under Simulated Solar Radiation Promoted by a Suitable Catalyst Selection

Considering water scarcity, photo-based processes have been presented as a depollution technique, which should be optimized in order to be applied in the future. For that, the addition of an active photocatalyst and the usage of solar radiation are mandatory steps. Thus, Fe3O4–SiO2–TiO2 was synthesized, and its performance was evaluated using simulated solar radiation and methylene blue as a model pollutant. Under optimal conditions, 86% degradation was attained in 1 h. These results were compared to recent published data, and the better performance can be attributed to both the operational conditions selection and the higher photocatalyst activity. Indeed, Fe3O4–SiO2–TiO2 was physico-chemically characterized with techniques such as XRD, N2 isotherms, spectrophotometry, FTIR, electrochemical assays and TEM.

Methylene blue adsorption by timbaúva (Enterolobium contortisiliquum)-derived materials

Liquid effluents from various dyeing industries often have a high concentration of dyes that diffuse into river systems and can be toxic and non-degradable in the environment. In this study, the potential of the use of timbaúva seed husks in the preparation of four adsorbents tested in the removal of methylene blue was analyzed: in natura, chemically activated material (q_max = 1.24 ± 0.04 mg g^-1), carbonized (q_max = 1.96 ± 0.03 mg g^-1), and activated carbon (q_max = 1.983 ± 0.04 mg g^-1). The adsorbents were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and CHN elemental analysis to assist in the proposed dye adsorption mechanism in the adsorbents tested. In the adjustment of the kinetic parameters, the pseudo-second order model was predominant by the statistical analysis of the ARE and R². The carbonized samples were better adjusted to Langmuir isotherms. The removal efficiency of the methylene blue dye in aqueous solutions at the concentrations and conditions studied was 86.78%. The coal from the seed husks of timbaúva has shown excellent performance in adsorption of the methylene blue dye and, therefore, can have technological application.

Layered platforms of Ti4O7 as flow-through anodes for intensifying the electro-oxidation of bentazon

In this study, we prepared Ti₄O₇ porous electrodes with continuous layered structures characterized by different layer-to-layer distance (from 2 to 10 μm) but the same total void fraction (88-90%), to modulate the electrodes' permeability and the volumetric electrochemical surface area (from 90 to 840 cm² cm^-3). These platforms were evaluated as anodes in the electro-oxidation (EO) of bentazon in a three-electrode cell under galvanostatic conditions, operated both in traditional batch (TB) or batch recycle flow-through (BRFT) modes. The performance was significantly enhanced when the liquid was recirculated through the lamellar structure of the electrodes. In BRFT mode, the electrode interlayer gap was found to be a key factor to control the bentazon and total organic carbon (TOC) conversions. For the best conditions evaluated (BRFT, 10 μm-interlayered Ti₄O₇ electrodes with a volumetric surface area of 90 cm² cm^-3), the effect of the applied current (1 or 3 mA) and liquid flow rate (10, 12 or 14 mL. min^-1) was investigated. Specific energy consumption (SEC) values were estimated to reveal the performance of each of the EO treatments from an energetic point of view. The use of 10 μm-interlayered Ti₄O₇ electrodes at 1 mA in BRFT mode at a flow rate of 14 mL min^-1 showed the best results, yielding 85% bentazon removal, 57% mineralization and SEC values of 0.006 kWh.g_TOC^-1 after 6 h of treatment. This contribution highlights the use of layered Ti₄O₇ electrodes as a promising strategy for intensifying EO processes, pointing to a trade-off between the accessibility to the internal electrode structure and the volumetric electrode surface area to enhance the contact between the target molecules and the hydroxyl radicals physisorbed on the electrode surface, while minimizing simultaneously the energy requirements.