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Environmental Research Jul 2024In our era, water pollution not only poses a serious threat to human, animal, and biotic life but also causes serious damage to infrastructure and the ecosystem. A set... (Review)
Review
In our era, water pollution not only poses a serious threat to human, animal, and biotic life but also causes serious damage to infrastructure and the ecosystem. A set of physical, chemical, and biological technologies have been exploited to decontaminate and/or disinfect water pollutants, toxins, microbes, and contaminants, but none of these could be ranked as sustainable and scalable wastewater technology. The photocatalytic process can harmonize the sunlight to degrade certain toxins, chemicals, microbes, and antibiotics, present in water. For example, transition metal oxides (ZnO, SnO, TiO, etc.), when integrated into an organic framework of graphene or nitrides, can bring about more than 90% removal of dyes, microbial load, pesticides, and antibiotics. Similarly, a modified network of graphitic carbon nitride can completely decontaminate petrochemicals. The present review will primarily highlight the mechanistic aspects for the removal and/or degradation of highly concerned contaminants, factors affecting photocatalysis, engineering designs of photoreactors, and pros and cons of various wastewater treatment technologies already in practice. The photocatalytic reactor can be a more viable and sustainable wastewater treatment opportunity. We hope the researcher will find a handful of information regarding the advanced oxidation process accomplished via photocatalysis and the benefits associated with the photocatalytic-type degradation of water pollutants and contaminants.
Topics: Wastewater; Waste Disposal, Fluid; Catalysis; Water Pollutants, Chemical; Water Purification; Photolysis; Photochemical Processes
PubMed: 38744372
DOI: 10.1016/j.envres.2024.118947 -
The Journal of Physical Chemistry. A Jul 2023Ozonolysis of isoprene is important in atmospheric chemistry because of the abundant emission of isoprene. This process produces the Criegee intermediates CHOO, methyl...
Ozonolysis of isoprene is important in atmospheric chemistry because of the abundant emission of isoprene. This process produces the Criegee intermediates CHOO, methyl vinyl ketone oxide (MVKO, CHC(CH)OO), and methacrolein oxide (MACRO, CHC(CH)CHOO). Gaseous MACRO was recently produced and identified in laboratories after photolysis of a mixture of 1,3-diiodo-2-methyl-prop-1-ene [(CHI)(CH)C═CHI] and O, but the conformation-dependent formation mechanism remains unexplored. We report conformation-distinct IR spectra of ()- and ()-(CHI)(CH)C═CHI isolated in solid -H. Upon irradiation near 300 nm of ()- and ()-(CHI)(CH)C═CHI in solid -H at 3.3 K, 3-iodo-2-methyl-prop-1-en-3-yl [•CHC(CH)CHI] radicals were characterized, with intense infrared absorption lines at 2991.3, 1458.7, 1434.7, 1317.4, 1190.4, 786.3, 677.9, and 467.2 cm and additional 11 weaker ones assigned to •CHC(CH)CHI and intense lines at 3108.5, 3076.2, 3028.5, 2970.0, 1174.2, 796.0, 683.6, and 609.5 cm and additional 7 weaker ones to ()•CHC(CH)CHI. The assignments were derived according to the behaviors of secondary photolysis at 495 and 460 nm and a comparison of the vibrational wavenumbers and IR intensities of the observed lines with those calculated with the B2PLYP-D3/aug-cc-pVTZ-pp method. These observations confirm that only the allylic C-I bond, not the vinylic one, was photodissociated at 290 nm, and in solid -H, the excess energy upon photolysis induced no conformational change. When O was present in the matrix, several intense lines at 1147.5, 1025.7, 914.4, and 728.7 cm, and 4 weaker ones were tentatively assigned to the adduct CHC(CH)CHIOO; the assignments were supported by O isotopic experiments. Unlike in the gaseous phase, the remaining C-I bond of this adduct could not break to form MACRO because of the efficient quenching in a low-temperature matrix.
PubMed: 37463498
DOI: 10.1021/acs.jpca.3c02170 -
The Journal of Physical Chemistry... Dec 2023Blebbistatin () derivatives are a visible light photocage platform. During the photocleavage process, intramolecular charge transfer (ICT) and cationic intermediates...
Blebbistatin () derivatives are a visible light photocage platform. During the photocleavage process, intramolecular charge transfer (ICT) and cationic intermediates play a decisive role. However, slow photolysis rate and low photolysis quantum yield are the main problems for 's derivatives. Herein, by introducing a substituted OCH group at the -position of the D ring, and derivatives with various leaving groups were synthesized and studied, and the photolysis performance was unveiled by steady-state spectra, photolysis rate experiments, photolysis quantum yield, and density functional theory calculations. Substituted OCH derivatives of may enhance the photolysis rate and increase the photolysis quantum yield because the electron-donating group can promote the ICT process and stabilize the cationic intermediate during the photolytic reaction. More generally, the insights gained from this structure-reactivity relationship may provide theoretical guidance and aid in the development of new highly efficient photoreactions.
PubMed: 38100086
DOI: 10.1021/acs.jpclett.3c02970 -
The Review of Scientific Instruments Nov 2023UV-vis spectroscopy is widely used for kinetic studies in physical chemistry, as species' absolute cross-sections are usually less sensitive to experimental conditions...
A white cell based broadband transient UV-vis absorption spectroscopy with pulsed laser photolysis reactors for chemical kinetics under variable temperatures and pressures.
UV-vis spectroscopy is widely used for kinetic studies in physical chemistry, as species' absolute cross-sections are usually less sensitive to experimental conditions (i.e., temperature and pressure). Here, we present the design and characterization of a multipass UV-vis absorption spectroscopy white cell coupled to a pulsed-laser photolysis flow reactor. The glass reactor was designed to facilitate studies of gas phase chemical reactions over a range of conditions (239-293 K and 10-550 Torr). Purged windows mitigate contamination from chemical precursors and photolysis products. We report the measured impact of this purging on temperature uniformity and the absorption length and present some supporting flow calculations. The combined optical setup is unique and enables the photolysis laser to be coaligned with a well-defined absorption pathlength probe beam. This alignment leverages the use of one long-pass filter to increase the spectrum flatness and increase the light intensity vs other systems that use two dichroic mirrors. The probe beam is analyzed with a dual exit spectrograph, customized to split the light between an intensified CCD and photomultiplier tube, enabling simultaneous spectrum and single wavelength detection. This multipass system yields a pathlength of ∼450 cm and minimum observable concentrations of ∼3.7 × 1011 molecule cm-3 (assuming cross-sections ∼1.2 × 10-17 cm2). The temperature profile across the reaction region is ±2 K, defined by the worst-case temperature of 239 K, validated by measurements of the N2O4 equilibrium constant. Finally, the system is implemented to study the simplest Criegee intermediate, demonstrating the instrument performance and advantages of simultaneous spectrum and temporal profile measurements.
PubMed: 37943165
DOI: 10.1063/5.0164733 -
Environmental Geochemistry and Health Dec 2023The impacts and mechanisms of natural water constituents, such as humic acid (HA), nitrates, iron and chloride ions, to the photodegradation of bisphenol A (BPA) were...
The impacts and mechanisms of natural water constituents, such as humic acid (HA), nitrates, iron and chloride ions, to the photodegradation of bisphenol A (BPA) were investigated in aqueous media under UV light irradiation. Due to the contributions of ·OH, O, O and BPA* to BPA photodegradation in pure water in 13.4, 7.7, 22.9 and 47.9%, respectively, BPA was attenuated through the reaction pathway of direct photodegradation more than self-sensitized photodegradation. About indirect photodegradation, BPA photolysis through inhibitory effect from HA was mainly by light screening effect and quenching effect was insignificant. NO- 3 and NO- 2 both showed inhibitory effect but due to different reactive oxidization species (ROS). The photodegradation of BPA was significantly enhanced by the addition of iron from the formation of ·OH and HO, due to iron-assisted indirect photolysis for the degradation process. A dual effect of chloride depending on the different concentration levels involved quenching and promotion effect on reactive photo-induced species (RPS). A simple linear model revealed that BPA photodegradation was significantly impacted by the interaction of the above factors. In natural water, the decreased photolytic rate of BPA was mainly attributed to triple-excited dissolved organic matter (DOM*), indicating that indirect photolysis was the primary transformation pathway of BPA. The detected photolysis products, such as nitrate and chlorinated products, suggest that there might be potential ecological risk of BPA photodegradation.
Topics: Photolysis; Chlorides; Hydrogen Peroxide; Iron; Water
PubMed: 38147143
DOI: 10.1007/s10653-023-01780-9 -
Environmental Toxicology and Chemistry Aug 2023While salinity can alter the photodegradation of hydrophobic organic compounds (HOCs), the cause of their altered kinetics in seawater is not well understood. Because...
While salinity can alter the photodegradation of hydrophobic organic compounds (HOCs), the cause of their altered kinetics in seawater is not well understood. Because HOC intermediate photoproducts are often more toxic than their parent compounds, characterizing the generation of intermediates in saline environments is needed to accurately predict their health effects. The present study investigated the influence of salinity on the generation of anthraquinone through the photolysis of anthracene and the generation of anthrone and 1-hydroxyanthraquinone from the photolysis of anthraquinone as well as their reactivities with hydroxyl radicals. This was conducted by measuring the photolysis rates of anthracene and anthraquinone and characterizing their product formation in buffered deionized water, artificial seawater, individual seawater halides (bromide, chloride, and iodide), dimethyl sulfoxide, furfuryl alcohol, and solutions of hydrogen peroxide. Salinity enhanced the persistence of anthraquinone by a factor >10 and altered its product formation, including the generation of the suspected carcinogen 1-hydroxyanthraquinone. In part, this was attributed to reactive oxygen species (ROS) scavenging by the seawater constituents chloride and bromide. In addition, anthraquinone and its hydroxylated products were found to be moderately to highly reactive with hydroxyl radicals, further illustrating their tendency to react with ROS in aqueous environments. The present study emphasizes the importance of considering the effects of salinity on organic contaminant degradation; it can significantly enhance the persistence of HOCs and alter their intermediate formation, subsequently impacting chemical exposure times and potential toxic effects on estuarine/marine organisms. Environ Toxicol Chem 2023;42:1721-1729. © 2023 SETAC.
Topics: Reactive Oxygen Species; Bromides; Chlorides; Water; Anthraquinones; Anthracenes; Organic Chemicals; Photolysis; Hydroxyl Radical; Water Pollutants, Chemical
PubMed: 37283213
DOI: 10.1002/etc.5687 -
The Science of the Total Environment Aug 2023Sulfamerazine (SM) is a commonly used antibiotic and have been widely used to control various bacterial infectious diseases. The structural composition of colored...
Sulfamerazine (SM) is a commonly used antibiotic and have been widely used to control various bacterial infectious diseases. The structural composition of colored dissolved organic matter (CDOM) is known to be a major factor that influences the indirect photodegradation of SM, yet the influence mechanism remains unknown. In order to understand this mechanism, CDOM from different sources was fractionated using ultrafiltration and XAD resin, and characterized using UV-vis absorption and fluorescence spectroscopy. The indirect photodegradation of SM in these CDOM fractions was then investigated. Humic acid (JKHA) and Suwannee River natural organic matter (SRNOM) were used in this study. The results showed that CDOM could be divided into four components (three humic-like components and one protein-like component), and terrestrial humic-like components C1 and C2 were found to be the main components that promote SM indirect photodegradation due to their high aromaticity. The indirect photodegradation of SM was much faster in low molecular weight (MW) solutions, whose structures were dominated by greater aromaticity and terrestrial fluorophores in JKHA and higher terrestrial fluorophores in SRNOM. The HIA and HIB fractions of SRNOM contained large aromaticity and high fluorescence intensities of C1 and C2, resulting in a greater indirect photodegradation rate of SM. The HOA and HIB fractions of JKHA had abundant terrestrial humic-like components and contributed more to SM indirect photodegradation.
Topics: Sulfamerazine; Dissolved Organic Matter; Organic Chemicals; Photolysis; Anti-Bacterial Agents; Rivers; Spectrometry, Fluorescence; China
PubMed: 37201832
DOI: 10.1016/j.scitotenv.2023.164231 -
The Science of the Total Environment Jun 2024Tioxazafen (TXF) is the first 1,2,4-oxadiazole nematicide. In the present study, the aqueous degradation of TXF was investigated in terms of hydrolysis and photolysis....
Tioxazafen (TXF) is the first 1,2,4-oxadiazole nematicide. In the present study, the aqueous degradation of TXF was investigated in terms of hydrolysis and photolysis. Under the irradiation of simulated sunlight, TXF degraded very fast in ultrapure water and buffers with half-lives (ts) <8.3 min. A sole photoproduct (PP) PP228a was isolated, and identified by spectroscopic means (UV, IR, HRMS, and H NMR) to be the thiophen-3-yl isomer converted from its thiophen-2-yl parent. Comparing with TXF, PP228a had quite extended ts ranging from 6.9 to 7.9 d. The photolysis kinetics of TXF and PP228a showed no pH-dependence, and varied for each individual compound as affected by nitrate, fulvic acid, and humic acid. Besides, both compounds were hydrolytically stable. 6 PPs of PP228a were identified, with two of them being its isomers. The mechanisms involved in the process included the biradical photosensitization, photoinduced electron transfer, and ring contraction-ring expansion reactions. The 48 h-EC to Daphnia magna was 0.808 mg/L for PP228a comparing to >1.12 mg/L for TXF, while the results of Vibrio fischeri assays indicated that one or more PPs of PP228a might have higher toxicity.
PubMed: 38880139
DOI: 10.1016/j.scitotenv.2024.173817 -
The Science of the Total Environment Feb 2024A wide range of contaminants of emerging concern (CECs) are known to photodegrade in the surface layers of natural waters and wastewater systems. Computer programs such... (Review)
Review
A wide range of contaminants of emerging concern (CECs) are known to photodegrade in the surface layers of natural waters and wastewater systems. Computer programs such as GCSolar, ABIWAS, APEX, EXAMS and WASP model the direct photolysis rates and half-lives of CECs, usually as a function of the solar irradiance, water molar light extinction, chemical molar light absorption and reaction quantum yield. These programs have been used extensively for studies in natural water systems in the northern hemisphere. However, their applicability to wastewater treatment systems such as waste stabilisation ponds and/or southern hemisphere conditions is not well studied. Here we present a comparative review of the major software used and their potential applicability to predicting direct photolysis rates and half-lives in wastewater. The newer equivalent monochromatic wavelength, approach, which enables the approximation of polychromatic photodegradation via a monochromatic wavelength is also discussed. Current software appears to be less suitable for modelling photodegradation in wastewater systems in the southern hemisphere than the northern hemisphere as their internal databases are based on data from natural waters in the northern hemisphere. This may be because there have been few attempts to model CEC photolysis in wastewater systems, particularly in the southern hemisphere. This indicates that either new software needs to be developed, or these programs need to be updated with data on wastewater matrices and/or the southern hemisphere. We anticipate this review will promote the adaptation of these programs as tools to further the understanding CEC photodegradation in wastewater treatment plants.
PubMed: 38040346
DOI: 10.1016/j.scitotenv.2023.168921 -
Physical Chemistry Chemical Physics :... Aug 2023Ethanol (CHOH) is one of the most common alcohol molecules observed in various space media (molecular clouds, star formation regions, and, highly likely, interstellar...
Ethanol (CHOH) is one of the most common alcohol molecules observed in various space media (molecular clouds, star formation regions, and, highly likely, interstellar ices), where it is exposed to light and ionizing radiation, leading to more complex organic molecules and eventually to the biologically important species. To better understand the radiation-induced evolution of ethanol molecules in icy media, we have examined the transformations of isolated CHOH and CDOH under the action of X-rays and vacuum ultraviolet (VUV) radiation in solid inert matrices (Ne, Ar, Kr, and Xe) at 4.4 K using Fourier transform infrared (FTIR) spectroscopy. The results obtained with X-ray irradiation demonstrate the formation of a variety of radiolysis products corresponding to dehydrogenation (CHCHOH˙, CHCHO, CHCHOH, CHCO˙, HCCO-H, HCCO, HCCO˙, CCO) and C-C bond rupture (HCO, HCO˙, CO, CH, and CH˙). The absorptions of the CHCHOH˙ radical related to the CCO stretching (the bands at 1249.1, 1247.0, 1246.2, and 1245.1 cm, in Ne, Ar, Kr, and Xe, respectively) were first tentatively characterized on the basis of comparison with available computational data. In addition, the CH⋯HO complex, which corresponds to dehydrogenation, was found followed by C-O bond cleavage. The results were confirmed by experiments with isotopic substitution. It was found that dehydrogenation strongly predominated in a xenon matrix, while skeleton bond rupture is more feasible in neon and argon. The matrix effect was attributed to a significant role of "hot" reaction channels in neon and argon, which are efficiently quenched due to relaxation in more polarizable xenon. The VUV photolysis (185 nm) in Ar and Xe matrices yields a similar set of products, except for CHCHOH˙ and CHCHOH, which were not found (the nonobservation of the former species may be explained by its efficient secondary photolysis). The plausible mechanisms of product formation and astrochemical implications of the results are discussed.
PubMed: 37566409
DOI: 10.1039/d3cp02834h