Efficient degradation of methyl orange and methylene blue in aqueous solution using a novel Fenton-like catalyst of CuCo-ZIFs

In this study, the synthesized CuCo-zeolitic imidazolate framework (ZIF) catalyst was used to degrade methyl orange (MO) and methylene blue (MB) in water via a novel Fenton-like catalytic reaction. Effects of catalyst dosage, H2O2 concentration, initial concentration of the contaminants, and reaction time were evaluated. The results showed that MO and MB decomposition efficiencies were highly influenced by CuCo-ZIF concentration. The presence of H2O2 accelerated the degradation reaction of both MO and MB. Although it took 100 min to complete the removal of MB, it was 60 min for MO. At concentrations of MO and MB lower than 40 mg·L−1, the catalyst showed an almost complete degradation. The CuCo-ZIF catalyst presented a good recyclability with more than 90% removal of MO and MB after four times and five times reuse, respectively. These results demonstrated that MO and MB were efficiently degraded by a Fenton-like catalyst of CuCo-ZIFs and its potential in industrial wastewater treatment.

A Simple g-C3N4/TNTs Heterojunction for Improving the Photoelectrocatalytic Degradation of Methyl Orange

In this work, highly ordered titanium dioxide nanotube arrays (TNTs) were first prepared by anodic oxidation method. Then, g-C3N4/TNTs heterojunctions were prepared by ultrasonically loading graphitic carbon nitride (g-C3N4) onto the TNTs. The morphology and crystal structure of TNTs and g-C3N4/TNTs were characterized by SEM and XRD. The photoelectrocatalytic (PEC) degradation of methyl orange (MO) by TNTs and g-C3N4/TNTs was studied in a PEC degradation system. The photocatalytic (PC), electrocatalytic (EC), and PEC degradation properties were compared, and the effect of pollutant concentration on the degradation performance of the catalysts was analyzed. According to the experimental results, the degradation rate of MO with TNTs only reaches 65.1% after 120 min, while the degradation rate of MO with g-C3N4/TNTs reaches 84.6% in the same time. Due to the synergistic effect of light and electricity, the PEC degradation efficiency of the two catalysts is greater than the sum of PC and EC degradation, proving that g-C3N4/TNTs heterojunctions provide excellent PEC performance for the degradation of MO.

Solvothermal Synthesis of ZnO Nanoparticles for Photocatalytic Degradation of Methyl Orange and p-Nitrophenol

The photocatalytic degradation of organic pollutants is an effective method of controlling environmental pollution. ZnO nanoparticles (ZnO NPs) were prepared by the solvothermal method and characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–visible diffuse reflectance spectroscopy (UV–Vis DRS). The results showed that the ZnO NPs had a uniform size of 25–40 nm, hexagonal wurtzite structure, and a band gap of 2.99 eV. The photocatalytic degradation of methyl orange (MO) and p-nitrophenol (PNP) was used as a model reaction to evaluate the photocatalytic activity of ZnO NPs. The photocatalytic degradation rates (pseudo-first-order kinetics) of MO and PNP were 92% (0.0128 min−1) and 56.2% (0.0042 min−1), respectively, with a 25 W ultraviolet lamp, MO/PNP concentration = 20 mg/L, ZnO NPs dose = 1.5 g/L, and time = 180 min. The photocatalytic mechanism of ZnO NPs and degradation pathways of MO and PNP were also proposed. The results provide valuable information and guidance for the treatment of wastewater via photocatalytic methods.