2,4-Dichlorophenoxyacetic acid (2,4-D) photodegradation on WO3-TiO2-SBA-15 nanostructured composite

Designing a Z-scheme rGO-SnS2 synergistic photocatalyst for photocatalytic mineralization of atrazine and 2,4-dichlorophenoxyacetic acid and applying machine learning for predictive modelling of photocatalytic performance

The extensive use of agrochemicals for crop protection and quality enhancement has raised environmental concerns due to their negative effects on human health. This study focuses on the design and synthesis of a Z-scheme rGO-SnS2 photocatalyst for wastewater treatment. rGO-SnS2 nanocomposites with varying SnS2 nanoparticle loadings were synthesized using a thermal decomposition method and characterized using various analytical techniques to confirm their composition, phase, structure, morphology, optical properties, and functional groups. The photocatalytic performance of the rGO-SnS2 nanocomposites was evaluated for the degradation of atrazine (ATZ) and 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solutions under natural sunlight. The optimized nanocomposite achieved fast and efficient degradation, with a removal efficiency of 91% for ATZ and 87% for 2,4-D within 3 minutes, compared to only 18% and 26% removal by pure rGO. The study also explored key parameters affecting photocatalytic performance, including catalyst loading, pH, dosage, and regeneration. The degradation pathways and major intermediates of ATZ and 2,4-D were identified using LC-MS analysis, and a detailed reaction mechanism was proposed based on scavenger and mineralization studies. Additionally, machine learning (ML) models, including Gaussian process (GP), artificial neural network (ANN), and support vector machine (SVM), were employed exclusively for predictive analysis of the photocatalytic performance. ANN demonstrated the best predictive capability, with an R 2 value of 0.974 and an error of 0.002. This work highlights the potential of rGO-SnS2 nanocomposites as effective photocatalysts for agrochemical mineralization, with ML aiding in performance prediction for real-world applications.

Degradation of Rhodamine B dye using the mesoporous material KIT-6/TiO2 photocatalyst obtained by in situ anchoring method

In this study, a novel synthesis approach was employed to create the KIT-6/TiO2 photocatalyst with different ratios of Si/Ti. The results of the X-ray diffraction revealed that incorporating TiO2 with the anatase phase maintained the mesoporous structure of KIT-6 (Korean Institute of Technology 6). The scanning electron microscope and transmission electron microscope images exhibited unobstructed mesopores, validating their anchoring within the internal structure of the support. Furthermore, nitrogen adsorption-desorption studies confirmed the presence of TiO2 within the pores. X-ray photoelectron spectroscopy (XPS) analysis corroborated the successful incorporation of TiO2, showing the presence of Ti4+ and Ti3+ species, with Ti3+ indicating the presence of oxygen vacancies that enhance photocatalytic performance. Photodegradation efficiency was assessed for Rhodamine B, achieving 95% and 86.5% for KIT-6/TiO2 (Si/Ti = 25) and KIT-6/TiO2 (Si/Ti = 75), respectively. The molar ratio Si/Ti = 25 exhibited higher activity, which can be attributed to a better distribution of active sites, as confirmed by the measurement of turnover frequency (TOF = 2.0 × 10-2 min-1). The stability of the KIT-6/TiO2 (Si/Ti = 25) has also been investigated, and stable performance in recycling photocatalytic reactions was obtained after four cycles of use. The scavengers used indicated that the superoxide anion radical (•O2-) and electron (e-) were the major active species. This study successfully demonstrated the incorporation of TiO2 into the walls of mesoporous materials using the ISA method, achieving high photocatalytic efficiency. Moreover, this method enabled superior performance with a reduced amount of photocatalyst compared to a pure TiO2 sample.

CdIn2Se4@chitosan heterojunction nanocomposite with ultrahigh photocatalytic activity under sunlight driven photodegradation of organic pollutants

This research focused on synthesizing a CdIn2Se4@Ch nanocomposite by doping CdIn2Se4 into chitosan using a photolysis assisted ultrasonic process. The aim was to enhance the photodegradation efficiency of ofloxacin and 2,4-dichlorophenoxyacetic acid under sunlight. The synthesized CdIn2Se4@Ch nanocomposite was investigated via different techniques, including XRD, XPS, FTIR, TEM, DSC, TGA, UV-Vis and PL. The study also investigated the influence of various reaction parameters, including the effects of inorganic and organic ions. The synthesized nanocomposite demonstrated exceptional efficiency, achieving 86 % and 95 % removal rates, with corresponding rate constants of 0.025 and 0.047 min-1. This performance surpasses that of CdIn2Se4 by approximately 1.35 and 2.25 times, respectively. The values of COD were decreased to 78 and 86 % for ofloxacin and 2,4-dichlorophenoxyacetic, while the TOC values decreased to 71 and 84 %, respectively, from their premier values. The improvement in performance is associated with the introduction of CdIn2Se4 into chitosan, resulting in the self-integration of Cd into the catalyst. This creates a localized accumulation point for electrons, enhancing the efficiency of charge separation and further reducing the surface charge of chitosan. Experimental evidence suggests that superoxide and hydroxyl radicals play a significant role in the photodegradation of pollutants. Additionally, the nanocomposite exhibits excellent stability and can be reused up to five times, indicating remarkable stability and reusability of the developed photocatalyst.

Greener Method for the Application of TiO2 Nanoparticles to Remove Herbicide in Water

TiO₂ nanoparticles have emerged as a great photocatalyst to degrade organic contaminants in water; however, the nanoparticles dispersed in water could be difficult to be recovered and potentially become contaminant. Herbicide like 2,4-dichlorophenoxyacetic acid (2,4-D) used in agriculture usually ends up with a large fraction remaining in water and sediment, which may cause potential risk to human health and the ecosystem. This study proposes a greener method to utilize TiO₂ as photocatalyst to remove 2,4-D from water. Accordingly, TiO₂ nanoparticles (10-45 nm) were synthesized and grafted on lightweight fired clay to generate a TiO₂-based floating photocatalyst. Experimental testing revealed that 60.2% of 2,4-D (0.1 mM) can be decomposed in 250 min under UV light with TiO₂-grafted lightweight fired clay floating on water. Degradation fits well into the pseudo-first-order kinetic model. The floating photocatalysts can degrade approximately 50% 2,4-D in 250 min under sunlight and the degradation efficiency is stable for cycles. The results revealed that the fabrication of floating photocatalyst could be a promising and greener way to remove herbicide contaminants in water using TiO₂.

TiO2-embedded mesoporous silica with lower porosity is beneficial to adsorb the pollutants and retard UV filter absorption: A possible application for outdoor skin protection

The purpose of the current investigation was to develop multifunctional TiO₂-embedded mesoporous silica incorporating avobenzone to protect against environmental stress through pollutant adsorption and UVA protection. We sought to explore the effect of the mesoporous porosity on the capability of contaminant capture and the suppression of avobenzone skin penetration. The porosity of the mesoporous silica was tuned by adjusting the ratio of template triblock copolymers (Pluronic P123 and F68). The Pluronic P123:F68 ratios of 3:1, 2:2, and 1:3 produced mesoporous silica with pore volumes of 0.66 (TiO₂/SBA-L), 0.47 (TiO₂/SBA-M), and 0.25 (TiO₂/SBA-S) cm³/g, respectively. X-ray scattering and electron microscopy confirmed the SBA-15 structure of the as-prepared material had a size of 3-5 μm. The maximum adsorbability of fluoranthene and methylene blue was found to be 43% and 53% for the TiO₂/SBA-S under UVA light, respectively. The avobenzone loaded into the mesoporous silica demonstrated the synergistic effect of in vitro UVA protection, reaching an UVA/UVB absorbance ratio of near 1.5 (Boots star rating = 5). The encapsulation of avobenzone into the TiO₂/SBA-S lessened cutaneous avobenzone absorption from 0.76 to 0.50 nmol/mg, whereas no reduction was detected for the TiO₂/SBA-L. The avobenzone-loaded TiO₂/SBA-S hydrogel exhibited a greater improvement in skin barrier recovery and proinflammatory mediator mitigation compared to the SBA-S hydrogel (without TiO₂). The cytokines/chemokines in the photoaged skin were reduced by two- to three-fold after TiO₂/SBA-S treatment compared to the non-treatment control. Our data suggested that the mesoporous formulation with low porosity and a specific surface area showed effective adsorbability and UVA protection, with reduced UVA filter absorption. The versatility of the developed mesoporous system indicated a promising potential for outdoor skin protection.