Efficient Oxidation of Methylene Blue via Catalytic Activation of Peroxymonosulfate via an Engineered δ-FeOOH/Pili Nutshell Biochar Composite

Sludge/TiO2 composite was synthesized from drinking water treatment sludge, as a waste material and TiO2 , by a sol- gel method. Various sludge adsorbent / TiO2 ratios (1:1, 1:2 and 2:1 w/w) were prepared, and characterized by transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray Fluorescence (XRF), and BET. The prepared composites were applied successfully for photodegradation of methylene blue (MB) dye from a solution. The photocatalytic degradation of MB dye was investigated using UV irradiation, or UV/H2O2. Initial dye concentration, solution pH, composite dosage, and UV irradiation time were applied to study the optimum conditions for MB degradation. The results revealed the highest MB dye degradation with composite (2:1). It was found that the maximum MB degradation efficiency was at pH=7, 4 h irradiation time, 0.125 g composite dose, and 50 ppm initial dye concentration. MB removal efficiency was 95.7% using UV irradiation, and 99.8% of that using UV/ H2O2. The rate of MB dye degradation followed the first order kinetics. Results from this study offer the best conditions for recycling drinking water treatment sludge, and use it for wastewater treatment.

Fe-glycerate microspheres as a heterogeneous catalyst to activate peroxymonosulfate for efficient degradation of methylene blue

In this work, we report the facile hydrothermal synthesis of manganese cobaltite nanoparticles (MnCo2O4.5 NPs) which can efficiently activate peroxymonosulfate (PMS) for the generation of sulfate free radicals (SO4˙−) and degradation of organic dyes. The synthesized MnCo2O4.5 NPs have a polyhedral morphology with cubic spinel structure, homogeneously distributed Mn, Co, and O elements, and an average size less than 50 nm. As demonstrated, MnCo2O4.5 NPs showed the highest catalytic activity among all tested catalysts (MnO2, CoO) and outperformed other spinel-based catalysts for Methylene Blue (MB) degradation. The MB degradation efficiency reached 100% after 25 min of reaction under initial conditions of 500 mg L−1 Oxone, 20 mg L−1 MnCo2O4.5, 20 mg L−1 MB, unadjusted pH, and T = 25 °C. MnCo2O4.5 NPs showed a great catalytic activity in a wide pH range (3.5–11), catalyst dose (10–60 mg L−1), Oxone concentration (300–1500 mg L−1), MB concentration (5–40 mg L−1), and temperature (25–55 °C). HCO3−, CO32− and particularly Cl− coexisting anions were found to inhibit the catalytic activity of MnCo2O4.5 NPs. Radical quenching experiments revealed that sulfate radicals are primarily responsible for MB degradation. A reaction sequence for the catalytic activation of PMS was proposed. The as-prepared MnCo2O4.5 NPs could be reused for at least three consecutive cycles with small deterioration in their performance due to low metal leaching. This study suggests a facile route for synthesizing MnCo2O4.5 NPs with high catalytic activity for PMS activation and efficient degradation of organic dyes.

Aims: The aim of this study is to evaluate the photocatalytic degradation of methylene blue dye on cuprous oxide/graphene nanocomposite. Background: Cuprous oxide (Cu2O) nanoparticles are among the metal oxides that demonstrated photocatalytic activity. However, the stability of Cu2O nanoparticles due to the fast recombination rate of electron/hole pairs remains a significant challenge in their photocatalytic applications. This in turn, leads to mismatching of the effective bandgap separation, tending to reduce the photocatalytic activity of the desired organic waste (MB). To overcome these limitations, graphene has been added to make nanocomposites with cuprous oxides. Objective: In this study, Cu2O/graphene nanocomposite was synthesized and evaluated for its photocatalytic performance of Methylene Blue (MB) dye degradation. Method: Cu2O/graphene nanocomposites were synthesized from graphite powder and copper nitrate using facile sol-gel method. Batch experiments have been conducted to assess the applications of the nanocomposites for MB degradation. Parameters such as contact time, catalyst dosage, and pH of the solution were optimized for maximum MB degradation. The prepared nanocomposites were characterized by using UV-Vis, FTIR, XRD, and SEM. The photocatalytic performance of Cu2O/graphene nanocomposites was compared against Cu2O nanoparticles for cationic MB dye degradation. Results: Cu2O/graphene nanocomposite exhibits higher photocatalytic activity for MB degradation (with a degradation efficiency of 94%) than pure Cu2O nanoparticle (67%). This has been accomplished after 180 min of irradiation under visible light. The kinetics of MB degradation by Cu2O/graphene composites can be demonstrated by the second-order kinetic model. The synthesized nanocomposite can be used for more than three cycles of phtocatalytic MB degradation. Conclusion: This work indicated new insights into Cu2O/graphene nanocomposite as highperformance in photocatalysis to degrade MB, playing a great role in environmental protection in relation to MB dye.

Activation of peroxymonosulfate by CoFe2O4 loaded on metal-organic framework for the degradation of organic dye.

Green synthesis of zinc oxide nanoparticles using Ficus carica leaf extract and their bactericidal and photocatalytic performance evaluation

Freestanding hematite nanofiber membrane for visible-light-responsive photocatalyst

Pt@TiO2@CNTs hierarchical structures were prepared by first functionalizing carbon nanotubes (CNTs) with nitric acid at 140 °C. Coating of TiO2 particles on the CNTs at 300 °C was then conducted by atomic layer deposition (ALD). After the TiO2@CNTs structure was fabricated, Pt particles were deposited on the TiO2 surface as co-catalyst by plasma-enhanced ALD. The saturated deposition rates of TiO2 on a-CNTs were 1.5 Å/cycle and 0.4 Å/cycle for substrate-enhanced process and linear process, respectively. The saturated deposition rate of Pt on TiO2 was 0.39 Å/cycle. The photocatalytic activities of Pt@TiO2@CNTs hierarchical structures were higher than those without Pt co-catalyst. The particle size of Pt on TiO2@CNTs was a key factor to determine the efficiency of methylene blue (MB) degradation. The Pt@TiO2@CNTs of 2.41 ± 0.27 nm exhibited the best efficiency of MB degradation.

CNT/TiO2 core-shell structures prepared by atomic layer deposition and characterization of their photocatalytic properties

Metal–organic cages (MOCs), with their unique cavity structures, abundant specific surface areas, and host–guest recognition capabilities, have been consistently demonstrated as catalysts that can significantly accelerate reaction rates and enhance substrate enrichment. Notably, although research has been devoted to the application of MOC in catalysis, studies focusing on the utilization of peroxymonosulfate (PMS) activation for pollutant degradation remain relatively limited. Herein, this study presented the synthesis of a novel cobalt-based metal–organic cage, {Co4(μ4-OCH3)(TBSC)}2L4·2DMF·CH3OH (L = 1,3-adamantanedicarboxylic acid), Ada-MOC, and evaluate its catalytic performance in PMS activation for methylene blue (MB) degradation. The results indicated that the Ada-MOC/PMS system showed a superior MB degradation efficiency of 99.9% within 30 min, with a kapp value 33 times higher than that of the PMS system. Furthermore, the Ada-MOC exhibited high stability and catalytic activity across a broad pH range and under diverse water quality conditions. Mechanistic studies revealed that nonradical pathways such as singlet oxygen (1O2) played a dominant role in the reaction process. Based on LC-TOF-MS analysis combined with DFT calculations, three potential degradation pathways for MB have been proposed. The Ada-MOC/PMS system developed in this research demonstrates considerable potential for practical application in organic wastewater remediation.

Efficient and sustainable photocatalytic degradation of dye in wastewater with porous and recyclable wood foam@V2O5 photocatalysts

In this work, a novel dual Z-scheme CdS/Ag2MoO4/β-Bi2O3 (CAB) composite heterojunction was synthesized, with the ultrafine CdS nanoparticles decorating two different-sized particles. In the beginning, the synergistic effect between BO and AMO makes the 10% Ag2MoO4/β-Bi2O3 (10AB) photocatalyst exhibit an optimal degradation efficiency of 87.1% for methylene blue (MB) of 10 mg·L−1 within 60 min; furthermore, its photocatalytic activity was enhanced by incorporating CdS nanoparticles on the surface of the AB heterojunction. The results showed that the 25% CdS/10% AMO/BO (25C10AB) composite achieved a maximum MB degradation efficiency of 99%. Optical and photoluminescence measurements showed that the dual Z-scheme CAB heterojunction has high crystallinity and efficient charge carrier migration and separation, which makes the samples more efficient for removing pollutants. Theoretical studies (DFT/FEM calculations) were performed to better understand the migration direction of e− and h+ in the photocatalytic degradation mechanism. This work provides a feasible approach to obtaining an efficient heterojunction composite photodegradation catalyst.

Fenton-like reactions with Fe-based metal–organic framework (MOF) catalysts have been extensively explored in the field of environmental remediation. However, easy precipitation of Fe2+/Fe3+ and the production of sludge under basic conditions caused catalyst loss and greatly limited their large-scale application in industry. The development of an Fe-free Fenton-like reaction is of extreme importance and remains in its infant stage. Herein, a series of Fe-free dual MOF nanoparticles (HKUST-1/ZIF-67-X) were fabricated by in situ coating of ZIF-67 on HKUST-1 and were systematically analyzed by various characterization techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and N2 adsorption–desorption isotherms. Subsequently, these materials were applied in catalyzing methylene blue (MB) degradation. The effects of several operation parameters, i.e., pH, H2O2 dosage, catalyst dosage, and reaction temperature, on MB degradation were investigated. It was unveiled that HKUST-1/ZIF-67-7% exhibited an outstanding catalytic activity without the production of any sludge, which could reach as high as 93.29% MB degradation efficiency within 40 min. This was attributed to the unique core–satellite histoarchitecture of HKUST-1/ZIF-67-7% and the synergistic effect between HKUST-1 and ZIF-67. The HKUST-1/ZIF-67-7% composite still achieved up to 80.17% MB degradation efficiency at the fifth catalysis cycle. Importantly, HKUST-1/ZIF-67-7% exhibited significant catalytic efficiency under a wide pH range (4.2–10.1) and top catalytic efficiency at the near neutral pH value. The low cost, environment benignancy, satisfactory degradation efficiency, wide pH application range, and excellent reusability emphasize its great application potential in Fenton-like degradation of pollutants. This contribution could provide a paradigm investigation for designing non-iron-based MOF catalysts to solve the increasingly pressing pollution issues.

Efficiency enhancement of photocatalytic activity under UV and visible light irradiation using ZnO/Fe3O4 heteronanostructures

Effect of Cr doping in CeO2 nanostructures on photocatalysis and H2O2 assisted methylene blue dye degradation