Synthesis and characterization of CoFe2O4/SiO2/Cu-MOF for degradation of methylene blue through catalytic sono-Fenton-like reaction

Boosting the adsorptive and photocatalytic performance of MIL-101(Fe) against methylene blue dye through a thermal post-synthesis modification

Photocatalytic degradation under ultra-low powered light is a viable advanced oxidation process technique against extensive emerging contaminants. As a new and remarkable class of nanoporous materials, metal-organic frameworks (MOFs), attract interest for the supreme adsorptive and photocatalytic functionalities. An outstanding MOF, MIL-101(Fe) chosen as a photocatalyst template for the synthesis of α-Fe2O3 by a simple thermal modification to improve the structural properties toward methylene blue (MB) eradication. Octahedron-like α-Fe2O3 photocatalyst (Modified MIL-101(Fe), M-MIL-101(Fe)) was superior in dispersion and separation properties in aqueous medium. Moreover, the adsorptive and catalytic performance was increased for modified form by ~ 7.3% and ~ 17.1% compared to pristine MIL-101(Fe), respectively. Synergistic improvement of MB removal achieved by simultaneous adsorption/degradation under 5-W LED irradiation. Parametric study indicated an 18.1% and 44.5% improvement in MB removal was observed by increasing pH from 4 to 10, and M-MIL-101(Fe) dose from 0.2 to 1 g L-1, respectively. MB removal followed the pseudo-second-order kinetics model and the process efficiency dropped by 38% as MB concentration increased from 5 to 20 mg L-1. Radical trapping tests revealed the significant role of [Formula: see text] and electron radicals as the major participants in dye degradation. A significant loss in the efficiency of M-MIL-101(Fe) was observed in the reusability tests that is good to study further. In conclusion, a simple thermal post-synthesis modification on MIL-101(Fe) improved its structural, catalytic, and adsorptive properties against MB.

Sonocatalytic Degradation of Chrysoidine R Dye Using Ultrasonically Synthesized NiFe2O4 Catalyst

The novel ultrasound-assisted co-precipitation method was successfully applied for the synthesis of the NiFe2O4 catalyst, which offered the advantages of lower particle size and better crystalline structure without affecting the phase planes. Furthermore, the efficacy of synthesized catalysts was evaluated using ultrasound-assisted catalytic degradation of Chrysoidine R dye. The study was designed to evaluate the effect of different parameters, such as pH, duty cycle, power output, and catalyst loading on Chrysoidine R dye degradation using a 5 wt% NiFe2O4 catalyst synthesized ultrasonically. At the optimized condition of 120 W ultrasonic power, 70% duty cycle, 3 pH, 0.5 g/L catalyst loading, and 160 min of reaction time, the best degradation of 45.01% was obtained. At similar conditions, the conventionally synthesized catalyst resulted in about 15% less degradation. Chrysoidine R dye degradation was observed to follow second-order kinetics. To accelerate the degradation, studies were performed using hydrogen peroxide at various loadings where it was elucidated that optimum use of 75 ppm loading showed the maximum degradation of 92.83%, signifying the important role of the co-oxidant in ultrasound-assisted catalytic degradation of Chrysoidine R dye. Overall, the present study clearly demonstrated the potential benefits of ultrasound in catalyst synthesis as well as in catalytic degradation.

Photocatalytic degradation effect and mechanism of Karenia mikimotoi by non-noble metal modified TiO2 loading onto copper metal organic framework (SNP-TiO2@Cu-MOF) under visible light

In this study, the SNP-TiO₂@Cu-MOF composite was prepared successfully by loading non-noble metal modified TiO₂ (SNP-TiO₂) on the surface of copper metal organic skeleton (Cu-MOF), and compared the inactivation efficiency of different photocatalysts to Karenia mikimotoi (K. mikimotoi) under visible light. The obtained photocatalyst had the characteristic crystal faces of Cu-MOF and SNP- TiO₂, and contained functional groups such as Cu-O, -COOH, N-O, P-O, etc., which indicated the structural stability of the photocatalyst. The band gap of SNP-TiO₂@Cu-MOF composite was 2.82 eV, and it had great light absorption ability in visible light region. It was proved to be a mesoporous adsorption material, which had a huge specific surface area (245 m²/g). Compared with other photocatalysts, SNP-TiO₂@Cu-MOF composite showed the strongest photocatalytic activity. When the concentration of composite material was set to 100 mg/L and the exposure time was 6 h, the visible light photocatalytic inactivation efficiency of K. mikimotoi was 93.75 %. By measuring various metabolic indexes of K. mikimotoi under the action of different photocatalysts for 1 h, it was confirmed that cell inactivation was due to the increased membrane permeability and degradation of photosynthetic pigments and main life proteins. This research showed that SNP-TiO₂@Cu-MOF composite material was full of great potential and application prospect in controlling the outbreak of eutrophication.

Degradation of Azithromycin from aqueous solution using Chlorine-ferrous- oxidation: ANN-GA modeling and Daphnia magna biotoxicity test assessment

Azithromycin (AZM), an antibacterial considered one of the most consumed drugs, especially during the period against the Covid 19 pandemic, and it is one of the persistent contaminants that can be released into aquatic ecosystems. The purpose of this study is to determine the efficacy of a Fenton-like process (chlorine/iron) for the degradation of AZM in an aqueous medium by determining the impact of several factors (the initial concentration of (FeSO₄, NaClO, pollutant), and the initial pH) on the degradation rate. The Response Surface Methodology (RSM) based on the Box-Wilson design as well as the Artificial Neural Network (ANN) modeling combined with a genetic algorithm (GA) approaches were used to determine the optimal levels of the selected variables and the optimal rate of degradation. The quadratic model of multi-linear regression developed indicated that the optimal conditions were a concentration of chlorine of 600 μM, the concentration of AZM is 32.8 mg/L, the mass of the catalyst FeSO₄ is 3.5 mg and a pH of 2.5, these optimal values gave a predicted and experimental yield of 64.05% and 70% respectively, the lack of fit test in RSM modeling (F₀ = 3.31 which is inferior to Fcritic (0.05, 10.4) = 5.96) indicates that the true regression function is not linear therefore, the ANN-GA modeling as non-linear regression indicated that the optimal conditions were a concentration of chlorine of 256 μM, the concentration of AZM is 5 mg/L, the mass of the catalyst FeSO₄ is 9.5 mg and a pH of 2.8, these optimal values gave a predicted and experimental yield of 79.69% and close to 80% respectively, Furthermore, biotoxicity tests were conducted to confirm the performance of our process using bio-indicators called daphnia (Daphnia magna), which demonstrated the efficacy of the like-Fenton process after 4 h of degradation.