Aeromonas hydrophila isolate showed the best decolorization of Reactive Black 5 (RB5) at the concentration of 100 mg L−1 on modified mineral salt medium among 42 bacterial isolates. Optimization of parameters for RB5 dye decolourization was studied under static condition. Under optimized condition, decolorization efficiency of RB5 by A. hydrophila was found to be 76% at 100 mg L−1 within 24 h. The optimum pH and temperature for the decolorization was 7 and 35 °C respectively. Biodegradation and decolorization of RB5, was monitored by UV–Vis spectrophotometry, Thin Layer Chromatography, Fourier Transform Infrared Spectroscopy and Gas Chromatography Mass Spectrometry analysis. The study has confirmed the potential of A. hydrophila isolated from textile effluent in degradation of RB5 and opened scope for future analysis in the treatment of textile effluent

In this work, the exploitation of the synthesized magnesium oxide nanoparticles and MgO-bentonite nanocomposite as an effective photocatalyst has been reported. They were utilized to study their applicability for the photocatalytic degradation of crystal violet in wastewater. Fourier-transform infrared (FTIR) spectra, X-ray powder diffraction (XRPD), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscope (TEM) were used for characterization. The photocatalytic efficiency of the synthesized photocatalysts for CV decomposition has been optimized in terms of several factors such as pH, contact time, the dose of the catalyst, and the dye concentration. The maximum degradation efficiency of CV was found to be 99.19% at the optimum state of pH value of 7, using 0.2 g of MgO NPs, while in the case of MgO-bentonite nanocomposite, the maximum degradation efficiency was decreased to 83.38%. The photocatalytic reaction mechanism was investigated using the scavenging reaction process, revealing that holes were majorly responsible for the degradation of CV. The kinetic data were suitable and best fitted by the pseudo-first-order kinetic model.

Background: Metronidazole (MNZ) is an antibiotic form that is considered as a dangerous environmental pollutant due to its widespread use as growth promoters in livestock and aquaculture operations along with its therapeutic application for humans. Purpose: The objective of this work was to conduct a comparative study between the efficiency of the adsorption and photocatalytic degradation of MNZ in an aqueous solution by using magnesium oxide nanoparticles (MgO NP) under different effects, as well as evaluate the performance, reusability and cost study. Materials and Methods: Several instruments such as XRD, EDX, SEM, and TEM were used to characterize the chemical composition and morphological properties of the synthesized MgO NP, while the GC-MS analysis was used to monitor the degradation pathway of MNZ particles within 180 min. The simple photo-batch reactor was used to investigate the degradation of MNZ under the effect of UV radiation, initial concentration of MNZ, pH, catalyst loading, inorganic salts addition, time, and temperature. Results: The degradation efficiency is mainly divided into two steps: 35.7% for maximum adsorption and 57.5% for photodegradation. Adsorption isotherm models confirmed that the process nature is chemisorption and appropriate Langmuir model, as well as to be a nonspontaneous and endothermic reaction according to the thermodynamic study. Adsorption constant during dark condition is smaller than typical adsorption equilibrium constant derived from the Langmuir-Hinshelwood kinetic model through photodegradation of MNZ that follows pseudo-first-order kinetics. Toxicity rates were reduced considerably after the photodegradation process to 88.21%, 79.84%, and 67.32% and 57.45%, 51.98%, and 43.87% by heamolytic and brine shrimp assays, respectively, for initial MNZ concentrations (20, 60, and 100 mg/L). Conclusion: We significantly recommend using MgO NP as a promising catalyst in the photodegradation applications for other organic pollutants in visible light.