Multi-criteria decision-making for prioritizing photocatalytic processes followed by TiO2-MIL-53(Fe) characterization and application for diazinon removal

Multi-criteria decision-making (MCDM) can introduce the best option based on evidence. We integrated the Analytic Hierarchy Process (AHP) and the Technique for Order of Preference by Similarity to the Ideal Solution (TOPSIS) to prioritize the alternatives for photocatalytic diazinon removal in a bench scale and characterized TiO2-MIL-53(Fe) for this purpose. Criteria and alternatives were listed based on systematic literature reviews and expert opinions. Then, AHP and TOPSIS questionnaires were developed and distributed to an expert panel for pairwise comparisons. We converted the linguistic variables into the corresponding fuzzy values and used R for mathematical calculations. Then, TiO2-MIL-53(Fe) was synthesized and characterized for diazinon removal under LED visible light. The AHP ranked criteria as availability > degradation efficiency > safety for the environment > material cost > energy consumption > mineralization efficiency > photocatalyst reusability > safety for personnel > equipment cost. Based on TOPSIS, the order of alternatives was TiO2-containing/Visible light > ZnO-containing/UV light > TiO2-containing/UV light > ZnO-containing/Visible light > WO3-containing/UV light. With a bandgap of 1.8 eV, TiO2-MIL-53(Fe) could remove 89.35% of diazinon at 10 mg/L diazinon concentration, 750 mg/L catalyst dose, pH 6.8, and 180-min reaction time. Hybrid AHP-TOPSIS identified the best option for photocatalytic diazinon removal from aqueous solutions. Thus, MCDM techniques can use systematic review results to overcome the uncertainty in designing experimental studies.

Photocatalytic removal of diazinon from aqueous solutions: a quantitative systematic review

Diazinon is a widely used pesticide that can be effectively degraded in aqueous solutions via photocatalytic oxidation. This quantitative systematic review was conducted to shed light on the various aspects of photocatalytic diazinon removal based on evidence. A systematic search was performed in Scopus, PubMed, Web of Science, Embase, and Ovid databases with keywords including diazinon, photocatalysis, and their equivalents. The search was limited to original articles in English published between January 1, 2010, and March 25, 2021. The results were expressed by descriptive statistics including mean, SD, median, and percentiles, among others. The initial electronic and manual search retrieved 777 articles, among which 41 studies comprising 49 trials were qualified for data synthesis. The reported diazinon degradation rate ranged from 2 to 100%, with a mean ± SD of 59.17 ± 28.03%. Besides, ZnO/UV, WO₃/UV, TiO₂/UV, and TiO₂/Vis, in sequence, were the most widely used processes with the highest efficacies. Solution pH in the range of 5-8, catalyst dose below 600 mg/L, diazinon initial concentration below 40 mg/L, and contact time of 20-140 min could be the optimum conditions. Diazinon degradation obeyed the first-order kinetic model with k_obs between 0.0042 and 1.86 min^-1 and consumed energy of 38.93-350.36 kWh/m³. Diazoxon and IMP were the most detected by-products of diazinon degradation although bioassay data were scarce. Based on the results, photocatalytic processes are very efficient in removing diazinon from aqueous solutions although more elaborate studies are needed to assess the mineralization rate and effluent toxicity.

Efficient photocatalytic degradation of metronidazole from aqueous solutions using Co/g-C3N4/Fe3O4 nanocomposite under visible light irradiation

Herein, the efficient degradation of a highly consumed antibiotic known as metronidazole (MNZ) in aqueous solutions using Co/g-C₃N₄/Fe₃O₄ nanocomposite under visible light irradiation was accomplished. Initially, the photocatalyst (Co/g-C₃N₄/Fe₃O₄) was synthesized by a simple hydrothermal method and then characterized by several analytical techniques, namely EDS, SEM, XRD, UV-vis DRS, and FTIR. The efficiency of the synthesized photocatalyst with regard to the degradation of the studied antibiotic (MNZ) under visible light irradiation was fully evaluated. The influential operational parameters affecting the efficiency of the degradation process such as pH (2-10), nanocomposite dosage (0.2-1 g/L), MNZ concentration (5-20 mg/L), and irradiation time (0-80 min) were optimized. The results revealed that the maximum degradation efficiency for MNZ was obtained under the following conditions: irradiation time of 60 min, pH = 8, MNZ concentration of 5 mg/L, and photocatalyst dosage of 0.7 g/L. In addition, the degradation of MNZ followed the pseudo-first-order kinetic model. The best rate constant (k) value was determined to be 0.0102 min^-1 with the correlation coefficient (R²) of 0.992. According to the results of the quenching tests, it was found out that hydroxyl radicals (OH°) were the main species responsible for the MNZ degradation. Furthermore, the applied photocatalyst (Co/g-C₃N₄/Fe₃O₄) exhibited a high level of recovery and stability after five cycles of reuse. Co/g-C₃N₄/Fe₃O₄/Vis system exhibited an excellent performance in the treatment of wastewater and real water samples. Finally, it was concluded that the synthesized nanocomposite could be potentially used as a promising and suitable photocatalyst in the degradation of other antibiotics.

Novel catalytic degradation of Diazinon with ozonation/mg-Al layered double hydroxides: optimization, modeling, and dispersive liquid-liquid microextraction

PURPOSE

In this study MgAl- layered double hydroxides (MgAl-LDH) nanoparticles were prepared by a simple and fast co-precipitation method and used as a catalyst in the ozonation process to degrade diazinon from aqueous solutions.

METHODS

The structure of the synthesized MgAl-LDH was investigated by X-ray diffraction pattern (XRD) and field emission scanning electron microscope-energy dispersive spectroscopy (FESEM-EDX). The response surface methodology (RSM) was used to investigate the effects of different parameters including of reaction time, initial diazinon concentration, pH, and LDH dose on the removal of diazinon by MgAl-LDH catalytic ozonation process. Central Composite Design (CCD) was employed for the optimization and modeling of the process. Dispersive liquid-liquid microextraction (DLLME) method was used to extract diazinon from aqueous samples. The GC-Mass analysis was performed to determine intermediate compounds during diazinon degradation reactions. To evaluate the process performance, TOC and COD removal were measured under optimum conditions.

RESULTS

The highest removal efficiency of 92% was observed in optimum conditions as follow; initial diazinon concentration: 120 mg/L, pH: 8.25, LDH dose: 750 mg/L, and reaction time: 70 min. The quadratic model was obtained with a good fit. The removal of COD and TOC were 80% and 74%, respectively.

CONCLUSION

This process can be suggested and used in the treatment of various industrial wastewaters.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00687-w.

Environmental Occurrence, Toxicity Concerns, and Degradation of Diazinon Using a Microbial System

Diazinon is an organophosphorus pesticide widely used to control cabbage insects, cotton aphids and underground pests. The continuous application of diazinon in agricultural activities has caused both ecological risk and biological hazards in the environment. Diazinon can be degraded via physical and chemical methods such as photocatalysis, adsorption and advanced oxidation. The microbial degradation of diazinon is found to be more effective than physicochemical methods for its complete clean-up from contaminated soil and water environments. The microbial strains belonging to Ochrobactrum sp., Stenotrophomonas sp., Lactobacillus brevis, Serratia marcescens, Aspergillus niger, Rhodotorula glutinis, and Rhodotorula rubra were found to be very promising for the ecofriendly removal of diazinon. The degradation pathways of diazinon and the fate of several metabolites were investigated. In addition, a variety of diazinon-degrading enzymes, such as hydrolase, acid phosphatase, laccase, cytochrome P450, and flavin monooxygenase were also discovered to play a crucial role in the biodegradation of diazinon. However, many unanswered questions still exist regarding the environmental fate and degradation mechanisms of this pesticide. The catalytic mechanisms responsible for enzymatic degradation remain unexplained, and ecotechnological techniques need to be applied to gain a comprehensive understanding of these issues. Hence, this review article provides in-depth information about the impact and toxicity of diazinon in living systems and discusses the developed ecotechnological remedial methods used for the effective biodegradation of diazinon in a contaminated environment.

Rare-Earth Metals-Doped Nickel Aluminate Spinels for Photocatalytic Degradation of Organic Pollutants

Visible-light-activated photocatalysts based on samarium-doped, europium-doped, and gadolinium-doped nickel aluminates (SmNA, EuNA, GdNA) were synthesized. The spinel crystalline structures of the doped mixed metal oxides were demonstrated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. The presence of the rare-earth metals (REMs) was confirmed by the energy-dispersive X-ray (EDX) studies. Ultraviolet-visible-near-infrared (UV-Vis-NIR) spectra revealed that the REMs-doped catalysts absorb in the full solar spectrum range covering both visible and near infrared wavelengths. Scanning electron microscopy (SEM) visualized the profound morphological alterations of the doped nickel aluminate samples. Consequently, the pore volume and the Brunauer-Emmett-Teller (BET) surface area decreased, while nanoparticles sizes increased. Fourier-transform infrared spectroscopy (FTIR) exposed that surfaces of REMs-doped nickel aluminates are rich in hydroxyl groups. Finally, the photocatalytic performance was notably increased through doping nickel aluminate (NA) with REMs; the highest activity was observed for EuNA.