-
Macromolecular Rapid Communications Aug 2023Poly(vinyl ketones) (PVKs) have received considerable attention over the past few decades due to their unique photochemistry and photodegradation properties under... (Review)
Review
Poly(vinyl ketones) (PVKs) have received considerable attention over the past few decades due to their unique photochemistry and photodegradation properties under ultraviolet (UV) light. Many PVKs rapidly undergo photodegradation under UV light. The side-chain carbonyl moieties of PVKs permit photolysis through Norrish type I or Norrish type II reaction mechanisms and can also be readily modified by nucleophilic addition reactions. These unique properties lead to this class of polymers serving as versatile scaffolds for generating functional materials. This review captures the evolution of synthetic routes to access well-defined PVKs, along with their photochemistry and photo-degradation pathways, and discusses recent and potential applications of these photodegradable materials.
Topics: Polymers; Ketones; Ultraviolet Rays; Photolysis; Photochemistry
PubMed: 37163690
DOI: 10.1002/marc.202300126 -
Chemosphere Sep 2023Paroxetine (abbreviated as PXT) has been widely used as one of the standard antidepressants for the treatment of depression. PXT has been detected in the aqueous...
Photodegradation fate of different dissociation species of antidepressant paroxetine and the effects of metal ion Mg: Theoretical basis for direct and indirect photolysis.
Paroxetine (abbreviated as PXT) has been widely used as one of the standard antidepressants for the treatment of depression. PXT has been detected in the aqueous environment. However, the photodegradation mechanism of PXT remains unclear. The present study aimed to use density functional theory and time-dependent density functional theory to study the photodegradation process of two dissociated forms of PXT in water. The main mechanisms include direct and indirect photodegradation via reaction with ·OH and O and photodegradation mediated by the metal ion Mg. Based on the calculations, PXT and PXT-Mg complexes in water are photodegraded mainly indirectly and directly. It was found that PXT and PXT-Mg complexes were photodegraded by H-abstraction, OH-addition and F-substitution. The main reaction of PXT indirect photolysis is OH-addition reaction, while the main reaction of PXT-Mg complex is H-abstraction. All the reaction pathways of H-abstraction, OH-addition and F-substitution are exothermic. PXT reacts more readily with ·OH or O in water than PXT. However, the higher activation energy of PXT with O indicates that the O reaction plays a minor role in the photodegradation pathway. The direct photolysis process of PXT includes ether bond cleavage, defluorination, and dioxolane ring-opening reaction. In the PXT-Mg complex, the direct photolysis process occurs via a dioxolane ring opening. Additionally, Mg in water has a dual effect on the direct and indirect photolysis of PXT. In other words, Mg can inhibit or promote their photolytic reactions. Overall, PXT in natural water mainly undergo direct and indirect photolysis reactions with ·OH. The main products include direct photodegradation products, hydroxyl addition products and F-substitution products. These findings provide critical information for predicting the environmental behavior and transformation of antidepressants.
Topics: Paroxetine; Photolysis; Dioxolanes; Water; Antidepressive Agents; Metals; Water Pollutants, Chemical; Kinetics
PubMed: 37279823
DOI: 10.1016/j.chemosphere.2023.139070 -
Chemosphere Oct 2023The three environmental degradation tests of hydrolysis, indirect photolysis and Zahn-Wellens microbial degradation were conducted according to the OECD and the US EPA...
The three environmental degradation tests of hydrolysis, indirect photolysis and Zahn-Wellens microbial degradation were conducted according to the OECD and the US EPA guidelines on DEMNUM, a typical linear perfluoropolyether polymer. Low mass degradation products that formed in each test were structurally characterized and indirectly quantified by liquid chromatography mass spectrometry (LC/MS) using a reference compound and an internal standard of similar structure. The degradation of the polymer was assumed to directly correlate with the appearance of lower mass species. The hydrolysis experiment at 50 °C showed the appearance of less than a dozen low mass species with increasing pH but at the negligible total estimated amount of ∼2 ppm relative to polymer. A dozen low mass perfluoro acid entities also appeared following the indirect photolysis experiment in synthetic humic water. Their maximum total amount was at ∼150 ppm relative to polymer. The largest total amount of low mass species formed during the Zahn-Wellens biodegradation test amounted to only ∼80 ppm relative to polymer. The Zahn-Wellens conditions tended to produce larger low mass molecules than the ones formed under photolysis. The results from all three tests indicate that the polymer is stable and non-degradable in the environment.
Topics: Biodegradation, Environmental; Chromatography, Liquid; Mass Spectrometry; Photolysis; Hydrolysis
PubMed: 37379990
DOI: 10.1016/j.chemosphere.2023.139331 -
Chemistry, An Asian Journal Nov 2023Phosphaketenes of divalent group 14 compounds can potentially serve as precursors for the synthesis of heavy multiple-bond systems. We have employed the Cbz...
Phosphaketenes of divalent group 14 compounds can potentially serve as precursors for the synthesis of heavy multiple-bond systems. We have employed the Cbz substituent ( Cbz=1,8-bis(3,5-ditertbutylphenyl)-3,6-ditertbutylcarbazolyl) to prepare such phosphaketenyltetrylenes [( Cbz)EPCO] (E=Ge, Sn, Pb). While the phosphaketenyltetrylenes are stable at ambient conditions, they can be readily decarbonylated photolytically. For the germylene and stannylene derivatives, dimeric diphosphene-type products [( Cbz)EP] (E=Ge, Sn) were obtained. In contrast, photolysis of the phosphaketenylplumbylene, via isomerisation of the [( Cbz)PbP] intermediate to [( Cbz)PPb], afforded an unsymmetric and incompletely decarbonylated product [( Cbz) Pb P CO] formally comprising a [( Cbz)PPb] and a [( Cbz)PbPCO] moiety.
PubMed: 37702378
DOI: 10.1002/asia.202300698 -
Chemosphere Aug 2023This study investigated the indirect photodegradation of sulfadimidine (SM) and sulfapyridine (SP) in the presence of chromophoric dissolved organic matter (CDOM), and...
This study investigated the indirect photodegradation of sulfadimidine (SM) and sulfapyridine (SP) in the presence of chromophoric dissolved organic matter (CDOM), and studied the influences of main marine factors (salinity, pH, NO and HCO). Reactive intermediate (RI) trapping experiments demonstrated that triplet CDOM (CDOM*) played a major role in the photodegradation of SM with a 58% photolysis contribution, and the contributions to the photolysis of SP were 32%, 34% and 34% for CDOM*, hydroxyl radical (HO·) and singlet oxygen (O), respectively. Among the four CDOMs, JKHA, with the highest fluorescence efficiency, exhibited the fastest rate of SM and SP photolysis. The CDOMs were composed of one autochthonous humus (C1) and two allochthonous humus (C2 and C3). C3, with the strongest fluorescence intensity, had the strongest capacity to generate RIs and accounted for approximately 22%, 11%, 9% and 38% of the total fluorescence intensity of SRHA, SRFA, SRNOM and JKHA, respectively, indicating the predominance of CDOM fluorescent components in the indirect photodegradation of SM and SP. These results demonstrated the photolysis mechanism: The photosensitization of CDOM occurred after its fluorescence intensity decreased, and a large number of RIs (CDOM*, HO· and O, etc.) were generated by energy and electron transfer, then these RIs reacted with SM and SP to cause photolysis. The increase in salinity stimulated the photolysis of SM and SP consecutively. The photodegradation rate of SM first increased and then decreased with increasing pH, whereas the photolysis of SP was remarkably promoted by high pH but remained stable at low pH. NO and HCO had little effect on the indirect photodegradation of SM and SP. This research may contribute to a better understanding of the fate of SM and SP in the ocean and provide new insights into the transformation of other sulfonamides (SAs) in marine ecological environments.
Topics: Dissolved Organic Matter; Sulfapyridine; Sulfamethazine; Photolysis; Seawater; Soil; Water Pollutants, Chemical
PubMed: 37149098
DOI: 10.1016/j.chemosphere.2023.138821 -
Environmental Toxicology and Chemistry Oct 2023The aqueous photolysis of four pharmaceuticals with varying fluorinated functional groups was assessed under neutral, alkaline, advanced oxidation, and advanced...
The aqueous photolysis of four pharmaceuticals with varying fluorinated functional groups was assessed under neutral, alkaline, advanced oxidation, and advanced reduction conditions with varying light sources. Solar simulator quantum yields were 2.21 × 10 mol Ei for enrofloxacin, 9.36 × 10 mol Ei for voriconazole, and 1.49 × 10 mol Ei for flecainide. Florfenicol direct photolysis was slow, taking 150 h for three degradation half-lives. Bimolecular rate constants between pharmaceuticals and hydroxyl radicals were 10 to 10 M s . Using a combined quantitative fluorine nuclear magnetic resonance spectroscopy ( F-NMR) and mass spectrometry approach, fluorine mass balances and photolysis product structures were elucidated. Enrofloxacin formed a variety of short-lived fluorinated intermediates that retained the aryl F motif. Extended photolysis time led to complete aryl F mineralization to fluoride. The aliphatic F moiety on florfenicol was also mineralized to fluoride, but the resulting product was a known antibiotic (thiamphenicol). For voriconazole, the two aryl Fs contributed more to fluoride production compared with the heteroaromatic F, indicating higher stability of the heteroaromatic F motif. The two aliphatic CF moieties in the flecainide structure remained intact under all conditions, further supporting the stability of these moieties found in per- and polyfluoroalkyl substances under a variety of conditions. The advanced treatment conditions generating hydroxyl radicals or hydrated electrons accelerated the degradation, but not the defluorination, of flecainide. The combination of F-NMR and mass spectrometry proved powerful in allowing identification of fluorinated products and verifying the functional groups present in the intermediates and products. The results found in the present study will aid in the understanding of which fluorinated functional groups should be incorporated into pharmaceuticals to ensure organofluorine byproducts are not formed in the environment and help determine the water-treatment processes that effectively remove specific pharmaceuticals and more generally fluorinated motifs. Environ Toxicol Chem 2023;00:1-12. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
PubMed: 37861370
DOI: 10.1002/etc.5773 -
The Science of the Total Environment Feb 2024Direct and indirect photolysis are important abiotic processes in aquatic environments through which plastics can be transformed physically and chemically. Transport of... (Review)
Review
Direct and indirect photolysis are important abiotic processes in aquatic environments through which plastics can be transformed physically and chemically. Transport of biodegradable plastics in water is influenced by vertical mixing and turbulent flow, which make biodegradable plastics remain susceptible to sunlight and photolysis despite their high density. In general, biodegradable plastics are composed of ester containing polymers (e.g., poly(butylene succinate), polyhydroxyalkanoate, and polylactic acid), whereas non-biodegradable plastics are composed of long chains of saturated aliphatic hydrocarbons in their backbones (e.g., polyethylene, polypropylene, and polystyrene). Based on the reviewed knowledge and discussion, we may hypothesize that 1) direct photolysis is more pronounced for non-biodegradation than for biodegradable plastics, 2) smaller plastics such as micro/nano-plastics are more prone to photodegradation and photo-transformation by direct and indirect photolysis, 3) the production rate of reactive oxygen species (ROS) on the surface of biodegradable plastics is higher than that of non-biodegradable plastics, 4) the photodegradation of biodegradable plastics may be promoted by ROS produced from biodegradable plastics themselves, and 5) the subsequent reactions of ROS are more active on biodegradable plastics than non-biodegradable plastics. Moreover, micro/nanoplastics derived from biodegradable plastics serve as more effective carriers of organic pollutants than those from non-biodegradable plastics and thus biodegradable plastics may not necessarily be more ecofriendly than non-biodegradable plastics. However, biodegradable plastics have been largely unexplored from the viewpoint of direct or indirect photolysis. Roles of reactive oxygen species originating from biodegradable plastics should be further explored for comprehensively understanding the photodegradation of biodegradable plastics.
Topics: Biodegradable Plastics; Photolysis; Reactive Oxygen Species; Plastics; Polypropylenes; Polystyrenes; Water Pollutants, Chemical
PubMed: 37981156
DOI: 10.1016/j.scitotenv.2023.168539 -
Environmental Science & Technology Feb 2024Fluorinated breakdown products from photolysis of pharmaceuticals and pesticides are of environmental concern due to their potential persistence and toxicity. While mass...
Fluorinated Pharmaceutical and Pesticide Photolysis: Investigating Reactivity and Identifying Fluorinated Products by Combining Computational Chemistry,F NMR, and Mass Spectrometry.
Fluorinated breakdown products from photolysis of pharmaceuticals and pesticides are of environmental concern due to their potential persistence and toxicity. While mass spectrometry workflows have been shown to be useful in identifying products, they fall short for fluorinated products and may miss up to 90% of products. Studies have shown that F NMR measurements assist in identifying and quantifying reaction products, but this protocol can be further developed by incorporating computations. Density functional theory was used to compute F NMR shifts for parent and product structures in photolysis reactions. Computations predicted NMR spectra of compounds with an R of 0.98. Computed shifts for several isolated product structures from LC-HRMS matched the experimental shifts with <0.7 ppm error. Multiple products including products that share the same shift that were not previously reported were identified and quantified using computational shifts, including aliphatic products in the range of -80 to -88 ppm. Thus, photolysis of fluorinated pharmaceuticals and pesticides can result in compounds that are polyfluorinated alkyl substances (PFAS), including aliphatic-CF or vinyl-CF products derived from heteroaromatic-CF groups. C-F bond-breaking enthalpies and electron densities around the fluorine motifs agreed well with the experimentally observed defluorination of CF groups. Combining experimental-computational F NMR allows quantification of products identified via LC-HRMS without the need for authentic standards. These results have applications for studies of environmental fate and analysis of fluorinated pharmaceuticals and pesticides in development.
PubMed: 38340057
DOI: 10.1021/acs.est.3c09341 -
Environmental Monitoring and Assessment Dec 2023In view of the widespread and distribution of several classes and types of organic contaminants, increased efforts are needed to reduce their spread and subsequent... (Review)
Review
In view of the widespread and distribution of several classes and types of organic contaminants, increased efforts are needed to reduce their spread and subsequent environmental contamination. Although several remediation approaches are available, adsorption and photodegradation technologies are presented in this review as one of the best options because of their environmental friendliness, cost-effectiveness, accessibility, less selectivity, and wider scope of applications among others. The bandgap, particle size, surface area, electrical properties, thermal stability, reusability, chemical stability, and other properties of silver nanoparticles (AgNPS) are highlighted to account for their suitability in adsorption and photocatalytic applications, concerning organic contaminants. Literatures have been reviewed on the application of various AgNPS as adsorbent and photocatalyst in the remediation of several classes of organic contaminants. Theories of adsorption have also been outlined while photocatalysis is seen to have adsorption as the initial mechanism. Challenges facing the application of silver nanoparticles have also been highlighted and possible solutions have been presented. However, current information is dominated by applications on dyes and the view of the authors supports the need to strengthen the usefulness of AgNPS in adsorption and photodegradation of more classes of organic contaminants, especially emerging contaminants. We also encourage the simultaneous applications of adsorption and photodegradation to completely convert toxic wastes to harmless forms.
Topics: Silver; Adsorption; Environmental Monitoring; Photolysis; Metal Nanoparticles; Kinetics
PubMed: 38112987
DOI: 10.1007/s10661-023-12194-6 -
A mini review on microwave and contemporary based biohydrogen production technologies: a comparison.Environmental Science and Pollution... Dec 2023Hydrogen gas, along with conventional fossil fuels, has been used as a green fuel with enormous potential. Due to the rapid depletion of fossil fuels, a new dimension of... (Review)
Review
Hydrogen gas, along with conventional fossil fuels, has been used as a green fuel with enormous potential. Due to the rapid depletion of fossil fuels, a new dimension of hydrogen production technology has arrived to reduce reliance on nonrenewable energy sources. Microwave-based hydrogen production is a more promising and cost-effective technology than other existing green hydrogen production methods such as fermentation and gasification. Microwave heating may be superior to traditional heating due to several advantages such as less power consumption compared to other methods, higher yield, and a higher rate of conversion. Compared to another process for hydrogen production, the microwave-driven process worked efficiently at lower temperatures by providing more than 70% yield. The process of production can be optimized by using properly sized biomass, types of biomass, water flow, temperature, pressure, and reactor size. This method is the most suitable, attractive, and efficient technique for hydrogen production in the presence of a suitable catalyst. Hot spots formed by microwave irradiation would have a substantial impact on the yield and properties of microwave-processed goods. The current techno-economic situation of various technologies for hydrogen production is discussed here, with cost, efficiency, and durability being the most important factors to consider. The present review shows that a cost-competitive hydrogen economy will necessitate continual efforts to increase performance, scale-up, technical prospects, and political backing.
Topics: Microwaves; Fermentation; Technology; Hydrogen; Fossil Fuels; Biomass; Biofuels
PubMed: 35840831
DOI: 10.1007/s11356-022-21979-0