A comparative approach of methylparaben photocatalytic degradation assisted by UV-C, UV-A and Vis radiations

Photocatalytic degradation of parabens: A comprehensive meta-analysis investigating the environmental remediation potential of emerging pollutant

The increasing prevalence of paraben compounds in the environment has given rise to concerns regarding their detrimental impacts on both ecosystems and human health. Over the past few decades, photocatalytic reactions have drawn significant attention as a method to accelerate the otherwise slow degradation of these pollutants. The current study aims to evaluate the current efficacy of the photocatalytic method for degrading parabens in aqueous solutions. An extensive literature review and bibliometric analysis were conducted to identify key research trends and influential areas in the field of photocatalytic paraben degradation. Studies were screened based on the predetermined inclusion and exclusion criteria, which led to 13 studies that were identified as being appropriate for the meta-analysis using the random effects model. Furthermore, experimental parameters such as pH, paraben initial concentration, catalyst dosage, light intensity, and contact time have been reported to have key impacts on the performance of the photocatalytic degradation process. A comprehensive quantitative assessment of these parameters was carried out in this work. Overall, photocatalytic techniques could eliminate parabens with an average degradation efficiency of >80 %. The findings of the Egger's test and the Begg's test were statistically not significant suggesting potential publication bias was not observed. This review provides a holistic understanding of the photocatalytic degradation of parabens and is anticipated to encourage more widespread adoption of photocatalytic procedures as a suitable method for the elimination of parabens from aqueous solutions, opening new avenues for future research in this direction.

Preparation of Novel C/N-Doped LaFeO3 Type Perovskite for Efficient Photocatalytic Degradation of Sodium Humate

LaFeO3 chalcocite precursor was prepared by solid-phase milling method, and LaFeO3-type chalcocite composite catalyst, referred to as LFCN catalyst, was synthesized by in situ doping of carbon and nitrogen (urea, melamine, dicyandiamide, and carbon powder), The catalytic performance of the catalysts was investigated by the different mass ratios of LaFeO3 chalcocite precursor and carbon and nitrogen (1:1, 1:2, and 2:1) and the degradation mechanism. Various characterization analyses, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET), showed that the doped composite LFCN catalysts exhibited a hemispherical network structure with a larger specific surface area than that of the pure phase LaFeO3 material. In addition, the LaFeO3 material adjusted the electronic structure of the original LaFeO3 chalcogenide material to a certain extent after in situ doping with organic C and N elements, which enhanced its lattice oxygen oxidation ability. In the study of the catalytic degradation of sodium humate solution under natural light conditions, the catalytic performance was significantly improved compared to that of the pure phase LaFeO3, and 10 mg of the catalyst degraded 30 mg/L of sodium humate solution in 50 min, with a degradation rate increasing from 40 to 98%. The degradation rate increased from 40 to 98% after 4 applications, indicating that the LFCN catalyst has good stability and significant catalytic degradation performance.

Toxicity and removal of parabens from water: A critical review

Parabens are biocides used as preservatives in food, cosmetics and pharmaceuticals. They possess antibacterial and antifungal activity due to their ability to disrupt cell membrane and intracellular proteins, and cause changes in enzymatic activity of microbial cells. Water, one of our most valuable natural resource, has become a huge reservoir for parabens. Halogenated parabens from chlorination/ozonation of water contaminated with parabens have shown to be even more persistent in water than other types of parabens. Unfortunately, there is dearth of data on their (halogenated parabens) presence and fate in groundwater which serves as a major source of drinking water for a huge population in developing countries. An attempt to neglect the presence of parabens in water will expose man to it through ingestion of contaminated food and water. Although there are reviews on the occurrence, fate and behaviour of parabens in the environment, they largely omit toxicity and removal aspects. This review therefore, presents recent reports on the acute and chronic toxicity of parabens, their estrogenic agonistic and antagonistic activity and also their relationship with antimicrobial resistance. This article further X-rays several techniques that have been employed for the removal of parabens in water and their drawbacks including adsorption, biodegradation, membrane technology and advanced oxidation processes (AOPs). The heterogeneous photocatalytic process (one of the AOPs) appears to be more favoured for removal of parabens due to its ability to mineralize parabens in water. However, more work is needed to improve this ability of heterogeneous photocatalysts. Perspectives that will be relevant for future scientific studies and which will drive policy shift towards the presence of parabens in our drinking waters are also offered. It is hoped that this review will elicit some spontaneous actions from water professionals, scientists and policy makers alike that will provide more data, effective technologies, and adaptive policies that will address the growing threat of the presence of parabens in our environment with respect to human health.

Cu2O/hollow mesoporous silica composites for the rapid and efficient removal of methylene blue

Cu₂O/hollow mesoporous silica (HMS) composite was synthesized using HMS as supporting material by the impregnation method. This composite displayed integrated physicochemical performance of Cu₂O and HMS, resulting in low density, large surface area and excellent dispersibility. The synthesized nano-sized composite of Cu₂O/HMS demonstrated rapid and effective removal for methylene blue with an efficiency of 99.8% with the reaction time of 5 min. Moreover, the Cu₂O/HMS composite exhibited high stability and present no obvious performance degradation after seven cycles. The dye removal efficiency stood up to 89% even after 15 cycles. The improved properties of Cu₂O/HMS are possibly the account of the collaborative effect between the mesoporous adsorption with Cu₂O photocatalysis.

Photodegradation comparison for methyl orange by TiO2, H2O2 and KIO4

The photodegradation of methyl orange in water by the catalyst TiO₂ or the oxidants (H₂O₂, KIO₄) or their combination (TiO₂ + H₂O₂, TiO₂ + KIO₄) under UV light illumination is studied. During the above process, as far as the photodiscoloration degree of methyl orange is concerned, the effect sequence is KIO₄ + TiO₂ >> KIO₄ > TiO₂ + H₂O₂ > TiO₂ > H₂O₂; as far as the photomineralization degree of methyl orange is concerned, the effect sequence is TiO₂ ≈ TiO₂ + H₂O₂ > H₂O₂ > KIO₄ + TiO₂ >> KIO₄; as for the catalysis of TiO₂, h⁺ plays more important role than HO·, the inorganic ions ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]) are generated, especially for the amount of [Formula: see text]. Active HO· is generated, we can measure HO· by terephthalic acid (TA) indirectly: TA reacts with HO· to form highly fluorescent product, namely 2-hydroxyterephthalic acid (TAOH).

ZnO, AgCl and AgCl/ZnO nanocomposites incorporated chitosan in the form of hydrogel beads for photocatalytic degradation of MB, E. coli and S. aureus

Significant improvement of effective and low-cost decolorization and disinfecting technologies is required to address the problems created by dyes and dangerous microorganisms from water and wastewaters. This article expresses the degradation of methylene blue (MB), Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as gram negative and positive bacteria via a chitosan/AgCl/ZnO (CS/AgCl/ZnO) nanocomposite hydrogel beads system as a photocatalyst under visible light irradiation. The techniques such as FT-IR, SEM, EDAX, TGA, and XRD were applied to recognize the synthesized beads. Decolorization and disinfection experimental results revealed that the hydrogel beads system effectively degrade MB and bacteria. Also, the effects of the initial amount of catalysts, pH, coions and initial concentration of dye on the photocatalytic decolorization were investigated. Moreover, kinetics analysis indicates that the photocatalytic degradation rate of MB and bacteria can be described by Langmuir-Hinshelwood (L-H) and Weibull inactivation models, respectively. We provide a reusable and recoverable effective organic/inorganic photocatalyst in the form of beads that could solve the disadvantages of powder photocatalytic, without reducing the efficiency.

Sonocatalytic degradation of butylparaben in aqueous phase over Pd/C nanoparticles

In the present work, the sonocatalytic degradation of butylparaben was investigated using Pd immobilized on carbon black as the sonocatalyst. The presence of 25 mg/L 10Pd/C significantly increased the removal rate of butylparaben and the observed kinetic constant increased from 0.0126 to 0.071 min^-1, while the synergy index between sonolysis and adsorption was 70.7%. The BP degradation followed pseudo-first-order kinetics with the apparent kinetic constant decreased from 0.071 to 0.030 min^-1 when the initial concentration of butylparaben increased from 0.5 to 2 mg/L. The process was being favored slightly under alkaline conditions. The presence of organic matter (20 mg/L humic acid) reduced the apparent kinetic constant more than two times. The addition of chlorides up to 250 mg/L did not significantly reduce the rate of reaction, while the presence of 250 mg/L bicarbonates reduced the observed kinetic constant from 0.071 to 0.0472 min^-1. The prepared catalyst retains the efficiency after five subsequent experiments since the apparent kinetic constant was only slightly decreased from 0.071 to 0.059 min^-1.

Comparison of Photocatalytic and Photosensitized Oxidation of Paraben Aqueous Solutions Under Sunlight

It is well-established that aquatic wildlife is exposed to natural and synthetic endocrine disrupting compounds which are able to interfere with the hormonal system. Although advanced oxidation processes (AOPs) have shown to be effective, their application is limited by a relatively high operational cost. In order to reduce the cost of energy consumed in the AOPs, widely available solar energy instead of UV light may be applied either as photocatalytic oxidation or as photosensitized oxidation. The main goal of the present study was to investigate the sunlight photodegradation of paraben mixture. Two processes, namely the photocatalytic oxidation with modified TiO2 nanoparticles and photosensitized oxidation with photosensitive chitosan beads, were applied. The oxidants were identified as singlet oxygen and hydroxyl radicals for photosensitized and photocatalytic oxidation, respectively. The toxicity, as well as ability to water disinfection of both processes under natural sunlight, has been investigated. Application of sunlight for the processes led to degradation of parabens. The efficiency of both processes was comparable. Despite the fact that singlet oxygen is weaker oxidant than hydroxyl radicals, the photosensitized oxidation seems to be more promising for wastewater purification, due to the possibility of chitosan bead reuse and more effective water disinfection. Graphical Abstractᅟ.