Photocatalytic degradation of deltamethrin by using Cu/TiO2/bentonite composite

Recent advances of application of bentonite-based composites in the environmental remediation

Bentonite-based composites have been widely utilized in the removal of various pollutants due to low cost, environmentally friendly, ease-to-operate, whereas the recent advances concerning the application of bentonite-based composites in environmental remediation were not available. Herein, the modification (i.e., acid/alkaline washing, thermal treatment and hybrids) of bentonite was firstly reviewed; Then the recent advances of adsorption of environmental concomitants (e.g., organic (dyes, microplastics, phenolic and other organics) and inorganic pollutants (heavy metals, radionuclides and other inorganic pollutants)) on various bentonite-based composites were summarized in details. Meanwhile, the effect of environmental factors and interaction mechanism between bentonite-based composites and contaminants were also investigated. Finally, the conclusions and prospective of bentonite-based composites in the environmental remediation were proposed. It is demonstrated that various bentonite-based composites exhibited the high adsorption/degradation capacity towards environmental pollutants under the specific conditions. The interaction mechanism involved the mineralization, physical/chemical adsorption, co-precipitation and complexation. This review highlights the effect of different functionalization of bentonite-based composites on their adsorption capacity and interaction mechanism, which is expected to be helpful to environmental scientists for applying bentonite-based composites into practical environmental remediation.

Photocatalytic degradation of four emerging antibiotic contaminants and toxicity assessment in wastewater: A comprehensive study

Excessive usage and unrestricted discharge of antibiotics in the environment lead to their accumulation in the ecosystem due to their highly stable and non-biodegradation nature. Photodegradation of four most consumed antibiotics such as amoxicillin, azithromycin, cefixime, and ciprofloxacin were studied using Cu2O-TiO2 nanotubes. Cytotoxicity evaluation of the native and transformed products was conducted on the RAW 264.7 cell lines. Photocatalyst loading (0.1-2.0 g/L), pH (5, 7 and 9), initial antibiotic load (50-1000 μg/mL) and cuprous oxide percentage (5, 10 and 20) were optimized for efficient photodegradation of antibiotics. Quenching experiments to evaluate the mechanism of photodegradation with hydroxyl and superoxide radicals were found the most reactive species of the selected antibiotics. Complete degradation of selected antibiotics was achieved in 90 min with 1.5 g/L of 10% Cu2O-TiO2 nanotubes with initial antibiotic concentration (100 μg/mL) at neutral pH of water matrix. The photocatalyst showed high chemical stability and reusability up to five consecutive cycles. Zeta potential studies confirms the high stability and activity of 10% C-TAC (Cuprous oxide doped Titanium dioxide nanotubes for Applied Catalysis) in the tested pH conditions. Photoluminescence and Electrochemical Impedance Spectroscopy data speculates that 10% C-TAC photocatalyst have efficient photoexcitation in the visible light for photodegradation of antibiotics samples. Inhibitory concentration (IC50) interpretation from the toxicity analysis of native antibiotics concluded that ciprofloxacin was the most toxic antibiotic among the selected antibiotics. Cytotoxicity percentage of transformed products showed r: -0.985, p: 0.01 (negative correlation) with the degradation percentage revealing the efficient degradation of selected antibiotics with no toxic by-products.

Remediation of pesticides using TiO2 based photocatalytic strategies: A review

Nowadays, pesticides are regarded as the most dangerous of the various organic pollutants, posing substantial environmental and human threats worldwide. Pesticide contamination has become one of the most crucial environmental issues due to its bio-persistence and bioaccumulation. Different conventional methods are being utilized for pesticide removal, yet pesticides are thought to be significantly present in the environment. The development and application of sophisticated wastewater treatment methods are being pursued to remove contaminants effectively, particularly pesticides. In the past several decades, nanoscience and nanotechnology have emerged as essential tools for the identification, removal, and mineralization of persistent pesticides by employing advanced nanomaterials such as pristine titanium dioxide (TiO₂), doped TiO₂, nanocomposites (NCs) TiO₂, and ternary nanocomposites (TNCs) TiO₂ by advanced oxidation processes (AOPs). Advancement in the characteristics of TiO₂ by doping, co-doping, construction of NCs and TNCs has contributed to the dramatic efficiency up-gradation by reducing band gap, solar active photocatalyst, enhancing PCA, high photostability, chemically inertness and multiple time reusability. Based on previous literature, utilizing La-TiO₂ NCs photocatalyst, the mineralization of pesticide (imidacloprid) attained up to 98.17% that is almost 40-53% greater than pristine TiO₂. The present review attempt to discuss the recent research performed on TiO₂ based nanoparticles (NPs) and NCs for photocatalytic mineralization of various pesticides. The basic mechanism of TiO₂ photocatalysis, types of reactors used for photocatalysis, and optimized experimental conditions of TiO₂ for pesticides mineralization are discussed.

Green photosensitisers for the degradation of selected pesticides of high risk in most susceptible food: A safer approach

Pesticides are the leading defence against pests, but their unsafe use reciprocates the pesticide residues in highly susceptible food and is becoming a serious risk for human health. In this study, mint extract and riboflavin were tested as photosensitisers in combination with light irradiation of different frequencies, employed for various time intervals to improve the photo-degradation of deltamethrin (DM) and lambda cyhalothrin (λ-CHT) in cauliflower. Different source of light was studied, either in ultraviolet range (UV-C, 254 nm or UV-A, 320-380 nm) or sunlight simulator (> 380-800 nm). The degradation of the pesticides varied depending on the type of photosensitiser and light source. Photo-degradation of the DM and λ-CHT was enhanced by applying the mint extracts and riboflavin and a more significant degradation was achieved with UV-C than with either UV-A or sunlight, reaching a maximum decrement of the concentration by 67-76%. The light treatments did not significantly affect the in-vitro antioxidant activity of the natural antioxidants in cauliflower. A calculated dietary risk assessment revealed that obvious dietary health hazards of DM and λ-CHT pesticides when sprayed on cauliflower for pest control. The use of green chemical photosensitisers (mint extract and riboflavin) in combination with UV light irradiation represents a novel, sustainable, and safe approach to pesticide reduction in produce.

Biological removal of deltamethrin in contaminated water, soils and vegetables by Stenotrophomonas maltophilia XQ08

The consideration of ecological and human health risk is an emerging concern with the excessive or inappropriate use of deltamethrin. In this study, the degradation conditions of the newly deltamethrin-degrading strain Stenotrophomonas maltophilia XQ08 were optimized, which were temperature 35 °C, pH 7.5, cell concentration 5.5 × 10⁸ cfu/mL, and substrate concentration 50 mg/L. Strain XQ08 could effectively degrade deltamethrin into three smaller molecular weight and lower toxic compounds. Enriched strain XQ08 was immobilized in a charcoal-alginate matrix and possessed more prominent biodegradability, reusability, storability and thermostability than free XQ08. In a continuous reactor system, immobilized XQ08 could averagely remove 78.81% of deltamethrin at the gradient influent dosages of 50, 75 and 100 mg/L within 30 d. Immobilized XQ08 introduced into the filed brown and yellow soils exhibited a superior degradation potential for deltamethrin with the half-lives of 1.77 and 2.04 d, which were 2.39 and 2.14 folds, or 6.09 and 5.47 folds faster than free XQ08 degradation (4.23 and 4.37 d) or natural dissipation (10.78 and 11.16 d), respectively. Moreover, application of free XQ08 decreased the persistence of deltamethrin in Brassica pekinensis and Brassica chinensis from 5.47 and 6.23 to 2.05 and 2.32 d, or by 62.52% and 62.76%, respectively. This study provides a feasible, effective and rapid biological removal technology for deltamethrin-contaminated environments in situ.

A Review on Metal Ions Modified TiO2 for Photocatalytic Degradation of Organic Pollutants

TiO2 is a semiconductor material with high chemical stability and low toxicity. It is widely used in the fields of catalysis, sensing, hydrogen production, optics and optoelectronics. However, TiO2 photocatalyst is sensitive to ultraviolet (UV) light; this is why its photocatalytic activity and quantum efficiency are reduced. To enhance the photocatalytic efficiency in the visible light range as well as to increase the number of the active sites on the crystal surface or inhibit the recombination rate of photogenerated electron–hole pairs electrons, various metal ions were used to modify TiO2. This review paper comprehensively summarizes the latest progress on the modification of TiO2 photocatalyst by a variety of metal ions. Lastly, the future prospects of the modification of TiO2 as a photocatalyst are proposed.