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This research paper investigates the photodegradation of Malachite Green (MG) using a new composite of river sediment (Sd) and synthesized TiO2 (Sd-TiO2-X%). TiO2 powder was synthesized using the sol–gel method and catalyst composites Sd-TiO2-X% (X = 10%, 15%, and 20%) were obtained using the wet impregnation. The photocatalytic performance of the composites was investigated using Box–Behnken design and results in the optimal parameters of %TiO2 (%) = 19.73, [MG] (ppm) = 42.25, and pH 9.58. Furthermore, Sd-TiO2-20% demonstrated exceptional stability and performance after undergoing five cycles. The scavenging tests for free radicals strongly confirmed the activity of superoxide ions (O2⋅−) and hydroxyl radicals (⋅OH) as the primary species responsible for degrading MG. The findings highlight the synergetic effect between river sediment and TiO2 in the photodegradation of organic pollutants-contaminated wastewater. This confirms the potential of valorizing sediments for promising and sustainable depollution applications using sediment-based materials. [ABSTRACT FROM AUTHOR]

This study focuses on the utilization of mineral carbonation as a means to capture carbon dioxide (CO2) from the atmosphere. The approach involves using various composites consisting of an inert matrix with an active phase. To evaluate the efficiency of mineral carbonation for CO2 sequestration, three composites were synthesized based on calcium-rich and calcium/magnesium-rich minerals using sol–gel techniques. The results obtained from the characterization techniques used, namely X-ray diffraction, infrared spectroscopy and scanning electron microscopy, demonstrate the formation of composite materials such as calcium oxide and calcium/magnesium oxides. After the bubbling process, these techniques confirmed the formation of stable calcium and magnesium carbonates. In addition, to assess the efficiency of the synthesized composites in CO2 capture, a Bernard's Calcimeter was used to determine the operating parameters favouring the mineral carbonation reaction. Analysing these operating parameters reveals that under atmospheric pressure and at room temperature, increasing the mass of the compound used leads to an increase in the percentage of captured CO2 up to 0.5 g, but this rate remains relatively constant when the mass is increased to 1 g. Additionally, increasing the particle size results in a higher CO2 capture rate. The initial pH of the solution plays a crucial role in promoting mineral carbonation, as an increase in the initial pH also leads to an increase in the CO2 fixation rate. It is essential for the medium to be basic, as this is one of the critical parameters contributing to the enhanced CO2 sequestration rate through the mineral carbonation method. [ABSTRACT FROM AUTHOR]

Nanocomposites of TiO2-clay were synthesized by the sol–gel route. The materials were characterized by XPS, XRD, UV–Vis DRS and BET surface area. Photocatalytic activity under UV irradiation (λmax ≈ 365 nm) was investigated by means of the phenol oxidation reaction. It was observed that the UV-photocatalytic property of TiO2-clay nanocomposite (SG) (Egap = 3.17 eV, SBET = 16.58 m2 g−1) for the phenol photodegradation was higher than that of commercial AEROXIDE® TiO2 P25. The activity of SG was greatly improved after silver photodeposition; in fact, the silver-photodeposited into SG highly enhanced the phenol degradation and mineralization efficiencies. The optimization of different experimental parameters, such as the photocatalyst amount, pH, temperature or hydrogen peroxide concentration on the phenol photodegradation under UV irradiation was studied with photodeposited catalyst 1.5%Ag/SG (Egap = 3.12 eV, SBET = 12.16 m2 g−1) based on the response surface methodology selecting composite central design as statistical model. Based on the ANOVA analysis, simulations explained a good fit to the experimental data involving a second-degree polynomial model with a model F-value of 73.31 and coefficient of determination (R2) value of 0.9959. Optimal experimental conditions were found to be a photocatalyst amount of 2 g L−1, solution pH of 5, temperature of 40 °C and hydrogen peroxide concentration of 8 mmol L−1. Under these optimized conditions, total degradation, 91% mineralization and non-toxicity were found, at 50 mg L−1 phenol during 120 min of reaction. Overall, pyrophyllite clay is very attractive as a natural and low-cost mineral for elaborating efficient photocatalysts. [ABSTRACT FROM AUTHOR]