Recent advances on advanced oxidation process for sustainable water management

Recent developments on advanced oxidation processes for degradation of pollutants from wastewater with focus on antibiotics and organic dyes

The existence of various pollutants in water environment contributes to global pollution and poses significant threats to humans, wildlife, and other living beings. The emergence of an effective, realistic, cost-effective, and environmentally acceptable technique to treat wastewater generated from different sectors is critical for reducing pollutant accumulation in the environment. The electrochemical advanced oxidation method is a productive technology for treating hazardous effluents because of its potential benefits such as lack of secondary pollutant and high oxidation efficiency. Recent researches on advanced oxidation processes (AOPs) in the period of 2018-2022 are highlighted in this paper. This review emphasizes on recent advances in electro-oxidation (EO), ozone oxidation, sonolysis, radiation, electro-Fenton (EF), photolysis and photocatalysis targeted at treating pharmaceuticals, dyes and pesticides polluted effluents. In the first half of the review, the concept of the AOPs are discussed briefly. Later, the influence of increasing current density, pH, electrode, electrolyte and initial concentration of effluents on degradation are discussed. Lastly, previously reported designs of electrochemical reactors, as well as data on intermediates generated and energy consumption during the electro oxidation and Fenton processes are discussed. According to the literature study, the electro-oxidation technique is more appropriate for organic compounds, whilst the electro-Fenton technique appear to be more appropriate for more complex molecules.

High-performance NiO@Fe3O4 magnetic core-shell nanocomposite for catalytic ozonation degradation of pharmaceutical pollution

Pharmaceuticals that are present in superficial waters and wastewater are becoming an ecological concern. Therefore, it is necessary to provide high-performance methods to limit the harmful ecological effects of these materials to achieve a sustainable environment. In this research, NiO@Fe3O4 nanocomposite was prepared by the co-precipitation method and utilized in the catalytic ozonation process for the degradation of 1-cyclopropyl-6-fluoro-4-oxo-7-piperazin-1-yl-quinoline-3-carboxylic acid (ciprofloxacin antibiotic), for the first time. The influencing parameters in the degradation process were analyzed and optimized via response surface methodology (RSM). The optimal ciprofloxacin removal efficiency (100%) was found at pH = 6.5, using 7.5 mg of the NiO@Fe3O4 nanocatalyst and 0.2 g L-1 h-1 ozone (O3) flow, applied over 20 min. Results showed a significant synergistic effect in the analyzed system, which makes the proposed catalytic ozonation process more efficient than using the catalyst and ozone separately. Also, based on the kinetic analysis data, the catalytic ozonation process followed the pseudo-first-order model. In addition, the nanocatalyst showed high recyclability and stability (88.37%) after five consecutive catalytic ozonation process cycles. In conclusion, the NiO@Fe3O4 nanocatalyst/O3 system can be effectively used for the treatment of pharmaceutical contaminants.

Electrochemical treatment of electroplating wastewater using synthesized GO/TiO2 nanotube electrode

The graphene oxide (GO) deposited TiO₂ nanotube (GO/TiO₂) electrode on a titania plate was prepared using a simple anodization method. The morphological and structural properties of TiO₂ and GO/TiO₂ electrodes have been studied using field emission scanning electron microscopy energy dispersive spectroscopy (FESEM-EDS), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Raman spectroscopy, Fourier transform infrared spectra (FT-IR), and X-ray photoelectron spectroscopy (XPS). FESEM-EDS analysis confirmed that the 13.56% wt of GO nanoparticles was formed over the TiO₂ substrate, with the thickness of the wall to be ∼300 nm. The crystallite size of GO/TiO₂, i.e., 19.53 nm, was confirmed by XRD analysis. Analysis of the UV-DRS spectrum showed the bandgap of the synthesized GO/TIO₂ nanotube electrode to be 3.052 eV. Box-Behnken design (BBD) under response surface methodology (RSM) was used to design the experiments. The effect of operating input parameters like pH, current (i), and degradation time (t) on % COD degradation (X₁) and energy consumed (X₂) were also examined. At optimum process parameters, the value of X₁ and X₂ were 57.61% and 15.00 kWh/m³, respectively. Possible intermediates were identified based on the GC-MS data analysis. Scavenger tests showed that •OH radical plays a major role in electroplating effluents degradation. Based on the results, the EO process using GO/TiO₂ electrodes could be considered a promising technique for electroplating effluent degradation due to high degradation efficiency.

A detailed review on advanced oxidation process in treatment of wastewater: Mechanism, challenges and future outlook

The presence of several contaminants in waterbodies raises global pollution and creates major risks to mankind, wildlife, as well as other living organisms. Development of an effective, feasible, cost-effective and eco-friendly approach for treating wastewater that is discharged from various industries is important for bringing down the deposition of contaminants into environment. Advanced oxidation process is an efficient technique for treating wastewater owing to its advantages such as high oxidation efficacy and does not produce any secondary pollutants. Advanced oxidation process can be performed through various methods such as ozone, Fenton, electrochemical, photolysis, sonolysis, etc. These methods have been widely utilized for degradation of emerging pollutants that cannot be destroyed using conventional approaches. This review focuses on wastewater treatment using advanced oxidation process. A brief discussion on mechanism involved is provided. In addition, various types of advanced oxidation process and their mechanism are explained in detail. Challenges faced during wastewater treatment process using oxidation, electrochemical, Fenton, photocatalysis and sonolysis are discussed elaborately. Advanced oxidation process can be viewed as potential approach for treating wastewater with certain modifications and solving challenges.

One-step synthesis of rod-on-plate like 1D/2D-NiMoO4/BiOI nanocomposite for an efficient visible light driven photocatalyst for pollutant degradation

Visible light active 1D/2D-NiMoO₄/BiOI nanocomposite photocatalyst has been constructed by single step solvothermal method. Various compositions of NiMoO₄/BiOI nanocomposites are prepared by loading different amounts of nickel molybdate (NiMoO₄) (1, 2, 3 wt%) to the bismuth oxy iodide (BiOI) and investigated by XRD, FTIR, SEM, EDAX, TEM, UV-vis DRS, and PL analysis. Among the as-prepared photocatalysts, 1 wt% NiMoO₄ incorporated BiOI (NMBI-1) showed superior photocatalytic activity with a rate constant of 0.0442 min^-1 for methylene blue degradation. While the bandgap values of pure BiOI and NiMoO₄ are 1.94 and 2.43 eV, respectively, the optimized NMBI-1 exhibited a lower bandgap energy of 1.64 eV, and showed about 2 and 3.7 times higher photodegradation ability than the pure NiMoO₄ and BiOI, respectively, towards MB removal under visible light. The NMBI-1 nanocomposite photocatalyst is stable even after four cycles, indicating an excellent photostability and recyclability. Charge carriers on the interface of NiMoO₄ and BiOI easily transferred via the newly formed heterojunction, thereby increasing the photocatalytic performance. Photochemically formed h⁺ and^.OH are found to be the major species in the MB removal under visible light illumination. Therefore, the 1D/2D-NiMoO₄/BiOI nanocomposite photocatalyst materials may be considered for the wastewater remediation processes.