Photocatalytic degradation of the herbicide chloridazon on mesoporous titania/zirconia nanopowders

Extra-modification of zirconium dioxide for potential photocatalytic applications towards environmental remediation: A critical review

Photocatalytic degradation is a valuable direction for eliminating organic pollutants in the environment because of its exceptional catalytic activity and low energy requirements. As one of the prospective photocatalysts, zirconium dioxide (ZrO₂) is a promising candidate for photoactivity due to its favorable redox potential and higher chemical stability. ZrO₂ has a high rate of electron-hole recombination and poor light-harvesting capabilities. Still, modification has demonstrated enhancements, especially extra-modification, and is therefore worthy of investigation. This present review provides a comprehensive overview of the extra-modifications of ZrO₂ for enhanced photocatalytic performance, including coupling with other semiconductors, doping with metal, non-metal, and co-doping with metal and non-metal. The extra-modified ZrO₂ showed superior performance in degrading the organic pollutant, particularly dyes and phenolic compounds. Interestingly, this review also briefly highlighted the probable mechanisms of the extra-modification of ZrO₂ such as p-n heterojunction, type II heterojunction, and Z-scheme heterojunction. The latter heterojunction with excellent electron-hole space separation improved the photoactivity. Extensive research on ZrO₂'s photocatalytic potential is presented, including the removal of heavy metals, the redox of heavy metals and organic pollutants, and the evolution of hydrogen. Modified ZrO₂'s photocatalytic effectiveness depends on its band position, oxygen vacancy concentration, and metal defect sites. The opportunities and future problems of the extra-modified ZrO₂ photocatalyst are also discussed. This review aims to share knowledge regarding extra-modified ZrO₂ photocatalysts and inspire new environmental remediation applications.

An eco-friendly and sustainable support of agave-fibers functionalized with graphene/TiO2:SnO2 for the photocatalytic degradation of the 2,4-D herbicide from the drinking water

In this research, we evaluated the photocatalytic performance of biodegradable composites for the removal of the 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide. The composite was composed by agave fibers (AgF), graphene-microplates (GM) and titanium dioxide TiO₂/SnO₂ (TSn) nanoparticles (NPs) and was named TSn + AgF/GM. Both, the TSn NPs and the GM were deposited on the AgF using the Dip-coating method. According to the analysis by X-Ray Diffraction (XRD), the crystalline phase for the TiO₂ and SnO₂ was anatase and tetragonal-rutile, respectively. The Scanning Electron Microscopy (SEM) images demonstrated that the AgF were completely saturated by the GM (which had average dimensions of 15 μm × 22 μm) and by conglomerations of TSn NPs with average size of 642 nm. The TSn NPs and the TSn + AgF/GM composite were evaluated for the photocatalytic degradation of the 2,4-D herbicide under ultraviolet-visible (UV-Vis) light and found a maximum degradation of 98.4 and 93.7% (after 4 h) for the TSn NPs and the TSn + AgF/GM composite, respectively. Reuse cycles were also performed and the degradation percentage decreased by 13.1% and by 7.8% (after 3 cycles of reuse) when the TSn NPs and the TSn + AgF/GM composite are employed, respectively. Scavenger experiments were also carried out and found that the oxidizing agents are mainly produced in the order of: •OH>•O₂^- > h⁺; then, the main oxidizing agents generated during the photocatalytic reaction were the hydroxyl radicals. Thus, the photocatalytic system studied in this work for the degradation of 2,4-D could pave the way for the development of new eco-friendly/floatable photocatalysts, which can be applied in wastewater-treatment plants.

Removal of Chloroacetanilide Herbicides from Water Using Heterogeneous Photocatalysis with TiO2/UV-A

Chloroacetanilide herbicides are widely used in the agricultural sector throughout the world. Because of their poor biodegradability, high water solubility, and long persistence, chloroacetanilide herbicides have a high potential to contaminate water, and conventional water treatment processes do not ensure sufficient removal. Therefore, heterogeneous photocatalysis using TiO2/UV-A was investigated for the degradation of alachlor, acetochlor, and metolachlor from water. Two commercially available TiO2 (P25 and AV-01) were used as photocatalysts. Different experimental setups were also tested. In addition, the toxicity of single herbicides and mixtures of their photocatalytic degradation products to the freshwater alga Chlorella kessleri was investigated via a growth inhibition test. The maximum removal efficiency for alachlor, acetochlor, and metolachlor was 97.5%, 93.1%, and 98.2%, respectively. No significant differences in the removal efficiency of chloroacetanilide herbicides were observed for the photocatalysts used. Although the concentrations of all herbicides during photocatalysis decreased, the toxicity of the resulting mixtures of degradation products increased or remained the same, indicating the formation of toxic degradation products.

Tailored functional materials as robust candidates to mitigate pesticides in aqueous matrices-a review

Pesticides are among the top-priority contaminants, which significantly contribute to environmental deterioration. Conventional techniques are not efficient enough to remove pollutants from environmental matrices. The development of functional materials has emerged as promising candidates to remove and degrade pesticides and related hazardous compounds. Furthermore, the nanohybrid materials with unique structural and functional characteristics, such as better material anchorage, mass transfer, electron-hole separation, and charged interaction make them a versatile option to treat and reduce pollutants from aqueous matrices. Herein, we present the current progress in the development of functional materials for the abatement of toxic pesticides. The physicochemical characteristics and pesticide-removal functionalities of various metallic functional materials (e.g., zirconium, zinc, titanium, tungsten, and iron), polymer, and carbon-based materials are critically discussed with suitable examples. Finally, the industrial-scale applications of the functional materials, concluding remarks, and future directions in this important arena are given.

Construction of Superhydrophobic Ru/TiCeOx Catalysts for the Enhanced Water Resistance of o-Dichlorobenzene Catalytic Combustion

In this paper, a simple method to enhance the H₂O resistance of Ru/TiCeO_x catalysts for o-DCB catalytic combustion by constructing superhydrophobic coating of phenyltriethoxysilane (PhTES) was proposed. The effect of PhTES content on the pore structure, specific surface area, H₂O resistance, contact angle (CA) value, and catalytic activity of the catalyst was studied. When water was added, the pristine Ru/TiCeO_x catalytic activity decreased by about 26%, while the Ru/TiCeO_x-16Ph activity hardly decreased. According to the analysis results of XRD, FT-IR, SEM, and CA, PhTES was closely coated on the surface of Ru/TiCeO_x to produce a more hydrophobic surface. The Ru/TiCeO_x-16Ph catalyst had strong hydrophobicity, and the contact angle was 159.8°, which not only significantly enhanced the water resistance and self-cleaning activity but also showed a good elimination temperature (T₉₀ = 341 °C) for the o-DCB. The enhanced water resistance of Ru/TiCeO_x-XPh catalysts resulted from the reduction of the active centers consumed (water occupying oxygen vacancy sites). The reaction mechanism of the Ru/TiCeO_x-16Ph catalyst based on surface oxygen species and the Deacon reaction was proposed. This method provided new idea for the design of a new water-resistant composite catalyst and promoted the practical application of the composite catalyst in the catalytic oxidation of o-DCB.

Current Trends in the Application of Nanomaterials for the Removal of Emerging Micropollutants and Pathogens from Water

Water resources contamination has a worldwide impact and is a cause of global concern. The need for provision of clean water is becoming more and more demanding. Nanotechnology may support effective strategies for the treatment, use and reuse of water and the development of next-generation water supply systems. The excellent properties and effectiveness of nanomaterials make them particularly suitable for water/wastewater treatment. This review provides a comprehensive overview of the main categories of nanomaterials used in catalytic processes (carbon nanotubes/graphitic carbon nitride (CNT/g-C₃N₄) composites/graphene-based composites, metal oxides and composites, metal–organic framework and commercially available nanomaterials). These materials have found application in the removal of different categories of pollutants, including pharmaceutically active compounds, personal care products, organic micropollutants, as well as for the disinfection of bacterial, viral and protozoa microbial targets, in water and wastewater matrices. Apart from reviewing the characteristics and efficacy of the aforementioned nanoengineered materials for the removal of different pollutants, we have also recorded performance limitations issues (e.g., toxicity, operating conditions and reuse) for their practical application in water and wastewater treatment on large scale. Research efforts and continuous production are expected to support the development of eco-friendly, economic and efficient nanomaterials for real life applications in the near future.