Mesopolymer modified with palladium phthalocyaninesulfonate as a versatile photocatalyst for phenol and bisphenol A degradation under visible light irradiation

Advances in photocatalytic degradation of organic pollutants in wastewaters: harnessing the power of phthalocyanines and phthalocyanine-containing materials

Access to clean water is increasingly challenging worldwide due to human activities and climate change. Wastewater treatment and utilization offer a promising solution by reducing the reliance on pure underground water. However, it is crucial to develop efficient and sustainable methods for wastewater purification. Among the emerging wastewater treatment strategies, photocatalysis has gained significant attention for decomposing organic pollutants in water, especially when combined with sunlight and a recoverable photocatalyst. Heterogeneous photocatalysts have distinct advantages, as they can be recovered and reused without significant loss of activity over multiple cycles. Phthalocyanine dyes, with their exceptional photophysical properties, are particularly valuable for homogeneous and heterogeneous photocatalysis. By immobilizing these photosensitizers in various supports, hybrid materials extend their light absorption into the visible spectrum, complementing most supports' limited UV light absorption. The novelty and research importance of this review stems from its discussion of the multifaceted approach to treating contaminated wastewater with phthalocyanines and materials containing phthalocyanines. It highlights key aspects of each study, including photocatalytic efficiency, recyclability characteristics, investigation of the generation of oxygen species responsible for degradation, identification of the major degradation byproducts for each pollutant, and others. Moreover, the review includes tables that illustrate and compare the various phthalocyanines and supporting materials employed in each study for pollutant degradation. Additionally, almost all photocatalysts mentioned in this review could degrade at least 5% of the pollutant, and more than 50 photocatalysts showed photocatalytic rates above 50%. When immobilized in some support, the synergistic effect of the phthalocyanine was visible in the photocatalytic rate of the studied pollutant. However, when performing these types of works, it is necessary to understand the degradation products of each pollutant and their relative toxicities. Along with this, recyclability and stability studies are also necessary. Despite the good results presented in this review, some of the works lack those studies. Moreover, none of the works mentions any study in wastewater.

Insights into the Photodegradation of the Contact Allergen Fragrance Cinnamyl Alcohol: Kinetics, Mechanism, and Toxicity

Fragrances can cause general health issues, and special concerns exist surrounding the issue of skin safety. Cinnamyl alcohol (CAL) is a frequent fragrance contact allergen that has various toxic effects on indiscriminate animals. In the present study, the photodegradation transformation mechanism of CAL and toxicity evolution during this process were examined. The results showed that CAL (50 μM) can be completely degraded after 90-min ultraviolet (UV) irradiation with a degradation rate of 0.086 min^-1 . Increased toxicity on bioluminescent bacteria was observed during this process, with lethality increasing from 10.6% (0 min) to 50.2% (90 min) under UV light irradiation. Further, the photodegradation mechanisms of CAL were explored to find the reason behind the increased toxicity observed. Laser flash photolysis and quenching experiments showed that O₂^•- , ¹ O₂ , and ^• OH were mainly responsible for CAL photodegradation, together with ³ CAL* and e_aq^- . The 5 main photodegradation products were cinnamyl aldehyde, benzaldehyde, benzenepropanal, cinnamic acid, and toluene, as identified using gas chromatography-mass spectrometry and liquid chromatography-quadrupole-time-of-flight-mass spectrometry. Once exposed to air, CAL was found to be easily oxidized to cinnamyl aldehyde and subsequently to cinnamic acid by O₂^•- - or ¹ O₂ -mediated pathways, leading to increased toxicity. Benzaldehyde exhibited bioreactive toxicity, increasing the toxicity through ^• OH-mediated pathways. Theoretical prediction of skin irritation indicated that cinnamyl aldehyde (0.83), benzenepropanal (0.69), cinnamyl aldehyde (0.69), and benzaldehyde (0.70) were higher than CAL (0.63), which may cause a profound impact on an individual's health and well-being. Overall, the present study advances the understanding of the photodegradation processes and health impacts of fragrance ingredients. Environ Toxicol Chem 2021;40:2705-2714. © 2021 SETAC.

Photochemical degradation of fragrance ingredient benzyl formate in water: Mechanism and toxicity assessment

Recently, fragrance ingredients have attracted increasing attention due to their imperceptible risks accompanying the comfortable feeling. To understand transformation mechanisms and toxicity evolution of benzyl formate (BF) in environment, its photochemical degradation in water was thoroughly studied herein. Results showed that 83.5% BF was degraded under ultraviolet (UV) irradiation for 30 min. Laser flash photolysis and quenching experiments demonstrated that triplet excited state (³BF*), O₂^•-, and ¹O₂ were three main reactive species found during BF photodegradation. Eight degradation intermediates, including benzaldehyde, benzyl alcohol, o-cresol, bibenzyl, benzyl ether, 1,2-diphenylethanol, benzoic acid, and benzylhemiformal, were mainly formed as identified by LC-Q-TOF/MS and GC-MS analyses. Furthermore, the degradation mechanism was explained as the bond cleavage of ³BF* and BF^•+, O₂^•-/¹O₂ oxidation, e_aq^- reduction, and ^•OH addition reactions. Aquatic assessment suggests that except benzyl alcohol, benzoic acid, and benzylhemiformal, all the products were persistent and could result in increased aquatic toxicity compared to original BF. Consequently, these degradation products may cause more toxicity to organisms if they remain accumulated in water environment for a long time.

Occurrence, endocrine-related bioeffects and fate of bisphenol A chemical degradation intermediates and impurities: A review

In recent decades, increasing attention has been directed toward the effects of bisphenol A (BPA) as an environmental pollutant, primarily due to its demonstrated endocrine-disruptive effects. A growing body of evidence indicates that many BPA derivatives also exhibit endocrine activity and other adverse biological properties. A review of the published literature was performed to identify BPA degradation intermediates resulting from chemical degradation processes of BPA, as well as BPA's associated co-pollutants. Products of biological metabolism were not included in this study. Seventy-nine chemicals were identified. Of these chemicals, a subset - those containing two 6-membered aromatic rings connected by a central ring-linking carbon - was identified, and a further literature review was conducted to identify demonstrated biological effects associated with the chemicals in this subset. The objectives of this review were to assess the potential risks to human and environmental health associated with BPA derivatives, characterize our current understanding of BPA's degradation intermediates and co-pollutants, and aid in the identification of compounds of interest that have received insufficient scrutiny.

Sono-photo-Fenton oxidation of bisphenol-A over a LaFeO3 perovskite catalyst

In this study, oxidation of bisphenol-A (IUPAC name - 2,2-(4,4-dihydroxyphenyl, BPA), which is an endocrine disrupting phenolic compound used in the polycarbonate plastic and epoxy resin industry, was investigated using sono-photo-Fenton process under visible light irradiation in the presence of an iron containing perovskite catalyst, LaFeO₃. The catalyst prepared by sol-gel method, calcined at 500°C showed a catalytic activity in BPA oxidation using sono-photo-Fenton process with a degradation degree and a chemical oxygen demand (COD) reduction of 21.8% and 11.2%, respectively. Degradation of BPA was studied by using individual and combined advanced oxidation techniques including sonication, heterogeneous Fenton reaction and photo oxidation over this catalyst to understand the effect of each process on degradation of BPA. It was seen, the role of sonication was very important in hybrid sono-photo-Fenton process due to the pyrolysis and sonoluminescence effects caused by ultrasonic irradiation. The prepared LaFeO₃ perovskite catalyst was a good sonocatalyst rather than a photocatalyst. Sonication was not only the effective process to degrade BPA but also it was the cost effective process in terms of energy consumption. The studies show that the energy consumption is lower in the sono-Fenton process than those in the photo-Fenton and sono-photo- Fenton processes.

Role of Free Radicals/Reactive Oxygen Species in MeHg Photodegradation: Importance of Utilizing Appropriate Scavengers

A variety of free radicals (FR)/reactive oxygen species (ROS) have been proposed to dominate methylmercury (MeHg) photodegradation, primarily based on the results of FR/ROS scavenger addition experiments. However, in addition to eliminating FR/ROS, the added scavengers may also affect the experimental results by altering some water chemical properties, resulting in a misleading assessment of the importance of FR/ROS. In this study, 20 common FR/ROS scavengers were evaluated in terms of their influence on light absorbance, pH, MeHg analysis, MeHg-dissolved organic matter (DOM) complexation, and the scavenger-induced degradation of MeHg. Only nine scavengers were identified to be appropriate for investigating MeHg photodegradation. By utilizing these appropriate scavengers, direct photodegradation of MeHg-DOM complexes was found to be the major pathway of MeHg photodegradation in Laoshan Reservoir water and Stone Old Beach seawater. In contrast, MeHg photodegradation in Ink River water primarily occurs through both ·OH and ³DOM* mediated indirect pathways and direct photodegradation of MeHg-DOM complexes. The diverse pathways of MeHg photodegradation in the tested water may be due to differences in water chemical properties. A severe overestimation of the role of FR/ROS was observed when several improper but commonly used scavengers were adopted, highlighting the necessity of utilizing appropriate scavengers.

Heterogeneous catalytic wet peroxide oxidation of simulated phenol wastewater by copper metal–organic frameworks

Two different porous copper metal–organic frameworks (Cu-MOFs) named as Cu₃(BTC)₂ and Cu(BDC) were synthesized and applied as heterogeneous catalysts for the catalytic wet peroxide oxidation (CWPO) of simulated phenol wastewater (100 mg L⁻¹).

Recent developments in heterogeneous photocatalytic water treatment using visible light-responsive photocatalysts: a review

This review summarizes the recent progress in the design, fabrication, and application of visible light-responsive photocatalysts.