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Photochemical & Photobiological... Apr 2024Photochemistry of the (n-BuN)[Pt(NO)] complex in acetonitrile was studied by means of stationary photolysis and nanosecond laser flash photolysis. The primary...
Photochemistry of the (n-BuN)[Pt(NO)] complex in acetonitrile was studied by means of stationary photolysis and nanosecond laser flash photolysis. The primary photochemical process was found to be an intramolecular electron transfer followed by an escape of an NO radical to the solution bulk. The spectra of two successive Pt(III) intermediates were detected in the microsecond time domain, and their spectral and kinetic characteristics were determined. These intermediates were identified as Pt(NO) and Pt(NO) complexes. Disproportionation of Pt(III) species resulted in formation of final Pt(II) products.
PubMed: 38430371
DOI: 10.1007/s43630-024-00550-5 -
Environmental Science & Technology Nov 2023Chlorine photolysis is an advanced oxidation process that relies on the combination of direct chlorination by free available chlorine, direct photolysis, and reactive...
Chlorine photolysis is an advanced oxidation process that relies on the combination of direct chlorination by free available chlorine, direct photolysis, and reactive oxidants to transform contaminants. In waters that contain bromide, free available bromine and reactive bromine species can also form. However, little is known about the underlying mechanisms or formation potential of disinfection byproducts (DBPs) under these conditions. We investigated reactive oxidant generation and DBP formation under dark conditions, chlorine photolysis, and radical-quenched chorine photolysis with variable chlorine (0-10 mg-Cl/L) and bromide (0-2,000 μg/L) concentrations, as well as with free available bromine. Probe loss rates and ozone concentrations increase with chlorine concentration and are minimally impacted by bromide. Radical-mediated processes partially contribute to the formation targeted DBPs (i.e., trihalomethanes, haloacetic acids, haloacetonitriles, chlorate, and bromate), which increase with increasing chlorine concentration. Chlorinated novel DBPs detected by high-resolution mass spectrometry are attributable to a combination of dark chlorination, direct halogenation by reactive chlorine species, and transformation of precursors, whereas novel brominated DBPs are primarily attributable to dark bromination of electron-rich formulas. The formation of targeted and novel DBPs during chlorine photolysis in waters with elevated bromide may limit treatment applications.
Topics: Disinfection; Chlorine; Bromides; Disinfectants; Bromine; Photolysis; Water Purification; Water Pollutants, Chemical; Halogenation; Chlorides; Oxidants
PubMed: 37363941
DOI: 10.1021/acs.est.3c00431 -
Physical Chemistry Chemical Physics :... Jul 2023The elusive hydrogen-bonded radical complex (˙SH⋯NH) consisting of ammonia (NH) and a mercapto radical (˙SH) has been generated through the 193 nm laser photolysis...
The elusive hydrogen-bonded radical complex (˙SH⋯NH) consisting of ammonia (NH) and a mercapto radical (˙SH) has been generated through the 193 nm laser photolysis of the molecular complex between NH and hydrogen sulfide (HS) in solid Ar- and N-matrixes at 10 K. The identification of ˙SH⋯NH with matrix-isolation IR spectroscopy and UV-vis spectroscopy is supported by N- and D-isotope labeling experiments and quantum chemical calculations at the B3LYP-D3(BJ)/6-311++G(3df,3pd) level of theory. In line with a large red shift of -172.2 cm for the frequency of the S-H stretching mode observed in ˙SH⋯NH ( free ˙SH), the radical ˙SH acts as a hydrogen donor, and NH acts as an acceptor. According to the calculations at the CCSD(T)/aug-cc-pVTZ level, the SH⋯N bonded structure ˙SH⋯NH (binding energy = 3.9 kcal mol) is more stable than the isomeric amidogen radical complex HSH⋯˙NH ( = 2.8 kcal mol) by 16.6 kcal mol. This is in sharp contrast to the photochemistry of the closely related HOH⋯NH complex, since the water-amidogen radical complex HOH⋯˙NH ( = 5.1 kcal mol) was generated under similar photolysis conditions, whereas the ammonia-hydroxyl radical complex ˙OH⋯NH ( = 7.9 kcal mol) is higher in energy by 9.3 kcal mol.
PubMed: 37387234
DOI: 10.1039/d3cp01689g -
Water Research Oct 2023Confronted with the imperative crisis of water quality deterioration, the pursuit of state-of-the-art decontamination technologies for a sustainable future never stops.... (Review)
Review
Confronted with the imperative crisis of water quality deterioration, the pursuit of state-of-the-art decontamination technologies for a sustainable future never stops. Fitting into the framework of suitability, advanced oxidation processes have been demonstrated as powerful technologies to produce highly reactive radicals for the degradation of toxic and refractory contaminants. Therefore, investigations on their radical-induced degradation have been the subject of scientistic and engineering interests for decades. To better understand the transient nature of these radical species and rapid degradation processes, laser flash photolysis (LFP) has been considered as a viable and powerful technique due to its high temporal resolution and rapid response. Although a number of studies exploited LFP for one (or one class of) specific reaction(s), reactions of many possible contaminants with radicals are largely unknown. Therefore, there is a pressing need to critically review its implementation for kinetic quantification and mechanism elucidation. Within this context, we introduce the development process and milestones of LFP with emphasis on compositions and operation principles. We then compare the specificity and suitability of different spectral modes for monitoring radicals and their decay kinetics. Radicals with high environmental relevance, namely hydroxyl radical, sulfate radical, and reactive chlorine species, are selected, and we discuss their generation, detection, and implications within the frame of LFP. Finally, we highlight remaining challenges and future perspectives. This review aims to advance our understandings of the implementation of LFP in radical-induced transient processes, and yield new insights for extrapolating this pump-probe technique to make significant strides in environmental implications.
Topics: Photolysis; Chlorides; Chlorine; Halogens; Lasers
PubMed: 37672949
DOI: 10.1016/j.watres.2023.120526 -
Journal of Hazardous Materials Jun 2024The use of vacuum-ultraviolet (VUV) photolysis in water treatment has been gaining significant interest due to its efficacy in degrading refractory organic contaminants... (Review)
Review
The use of vacuum-ultraviolet (VUV) photolysis in water treatment has been gaining significant interest due to its efficacy in degrading refractory organic contaminants and eliminating oxyanions. In recent years, the reactive species driving pollutant decomposition in VUV-based advanced oxidation and reduction processes (VUV-AOPs and VUV-ARPs) have been identified. This review aims to provide a concise overview of VUV photolysis and its advancements in water treatment. We begin with an introduction to VUV irradiation, followed by a summary of the primary reactive species in both VUV-AOPs and VUV-ARPs. We then explore the factors influencing VUV-photolysis in water treatment, including VUV irradiation dose, catalysts or activators, dissolved gases, water matrix components (e.g., DOM and inorganic anions), and solution pH. In VUV-AOPs, the predominant reactive species are hydroxyl radicals (˙OH), hydrogen peroxide (HO), and ozone (O). Conversely, in VUV-ARPs, the main reactive species are the hydrated electron (e) and hydrogen atom (˙H). It is worth noting that VUV-based advanced oxidation/reduction processes (VUV-AORPs) can transit between VUV-AOPs and VUV-ARPs based on the externally added chemicals and dissolved gases in the solution. Increase of the VUV irradiation dose and the concentration of catalysts/activators enhances the degradation of contaminants, whereas DOM and inorganic anions inhibit the reaction. The pH influences the redox potential of ˙OH, the speciation of contaminants and activators, and thus the overall performance of the VUV-AOPs. Conversely, an alkaline pH is favored in VUV-ARPs because e predominates at higher pH.
PubMed: 38691932
DOI: 10.1016/j.jhazmat.2024.134432 -
Ecotoxicology and Environmental Safety Sep 2023Pyriclobenzuron (PBU) is a novel molluscicide developed to control Pomacea canaliculate, and little information on its environmental fate has been published. In this...
Pyriclobenzuron (PBU) is a novel molluscicide developed to control Pomacea canaliculate, and little information on its environmental fate has been published. In this study, the photolysis of PBU in an aqueous environment was simulated using a xenon lamp. Results showed that the photolysis of PBU in water followed first-order kinetics, exhibiting a t of 95.1 h and 83.6 h in Milli-Q water and river water, respectively. Two main photolysis products (PPs) were detected by HPLC-UV and identified by UPLC-Q/TOF MS, which were formed via the hydroxylation and photocatalytic hydro-dehalogenation of PBU, respectively. The initial relative abundance of photolysis product 1 (PP-1) in Milli-Q water was 1.55 times higher than that in river water. PP-1 was detected at 26.5 % and 76.8 % of the maximum relative abundance in the river water and Milli-Q water after 720 h, respectively. Photolysis product 2 (PP-2) was stable in water because of its weak hydrophilicity. The PP-2 detected after 720 h in Milli-Q water and river water was 93.7 % and 93.5 % of the maximum relative abundance, respectively. Finally, ECOSAR software was used to evaluate the acute aquatic toxicity of PBU and its PPs, revealing that the PPs had lower toxicity levels to non-target aquatic organisms.
Topics: Sunlight; Kinetics; Water; Photolysis; Water Pollutants, Chemical
PubMed: 37473704
DOI: 10.1016/j.ecoenv.2023.115272 -
Environmental Science & Technology Jun 2024Hydrogen-tuned 185 nm vacuum ultraviolet (VUV/H) photolysis is an emerging technology to destroy per- and polyfluoroalkyl substance (PFAS) in brine. This study...
Promotive Effects of Chloride and Sulfate on the Near-Complete Destruction of Perfluorocarboxylates (PFCAs) in Brine via Hydrogen-tuned 185-nm UV Photolysis: Mechanisms and Kinetics.
Hydrogen-tuned 185 nm vacuum ultraviolet (VUV/H) photolysis is an emerging technology to destroy per- and polyfluoroalkyl substance (PFAS) in brine. This study discovered the promotive effects of two major brine anions, i.e., chloride and sulfate in VUV/H photolysis on the hydrated electron (e) generation and perfluorocarboxylates (PFCAs) destruction and established a kinetics model to elucidate the promotive effects on the steady-state concentration of e ([e]). Results showed that VUV/H achieved near-complete defluorination of perfluorooctanoic acid (PFOA) in the presence of up to 1000 mM chloride or sulfate at pH 12. The defluorination rate constant () of PFOA peaked with a chloride concentration at 100 mM and with a sulfate concentration at 500 mM. The promotive effects of chloride and sulfate were attributed to an enhanced generation of e via their direct VUV photolysis and conversion of additionally generated hydroxyl radical to e by H, which was supported by a linear correlation between the predicted [e] and experimentally observed . The value increased from pH 9 to 12, which was attributed to the speciation of the H/e pair. Furthermore, the VUV system achieved >95% defluorination and ≥99% parent compound degradation of a concentrated PFCAs mixture in a synthetic brine, without generating any toxic perchlorate or chlorate.
Topics: Kinetics; Photolysis; Ultraviolet Rays; Fluorocarbons; Sulfates; Hydrogen; Chlorides; Salts; Water Pollutants, Chemical; Caprylates
PubMed: 38808621
DOI: 10.1021/acs.est.3c10552 -
Journal of Environmental Sciences... Dec 2023Vacuum ultraviolet (VUV) photolysis is a facile method for volatile organic compounds (VOCs) elimination, but is greatly limited by the relatively low removal efficiency...
Vacuum ultraviolet (VUV) photolysis is a facile method for volatile organic compounds (VOCs) elimination, but is greatly limited by the relatively low removal efficiency and the possible secondary pollution. To overcome above drawbacks, we developed an efficient method for VOCs elimination via VUV photolysis coupled with wet scrubbing process. In this coupled process, volatile toluene, a representative of VOCs, was oxidized by the gas-phase VUV photolysis, and then scrubbed into water for further oxidation by the liquid-phase VUV photolysis. More than 96% of toluene was efficiently removed by this coupled process, which was 2 times higher than that in the gas-phase VUV photolysis. This improvement was attributed to the synergistic effect between gas-phase and liquid-phase VUV photolysis. O and HO are the predomination reactive species for the toluene degradation in this coupled process, and the generation of O in gas-phase VUV photolysis can efficiently enhance the HO production in liquid-phase VUV photolysis. The result from in-situ proton transfer reaction ionization with mass analyzer (PTR-MS) further suggested that most intermediates were trapped by the wet scrubbing process and efficiently oxidized by the liquid-phase VUV photolysis, showing a high performance for controlling the secondary pollution. Furthermore, the result of stability test and the reuse of solution demonstrated that this coupled process has a highly stable and sustainable performance for toluene degradation. This study presents an environmentally benign and highly efficient VUV photolysis for gaseous VOCs removal in the wet scrubbing process.
Topics: Photolysis; Vacuum; Volatile Organic Compounds; Oxidation-Reduction; Gases; Toluene
PubMed: 37673533
DOI: 10.1016/j.jes.2022.05.002 -
Environment International Jul 2023The photochemical behaviors of chiral pollutants in aqueous solutions are rarely studied using chiral monomers, which may hamper their precise risk assessment and lead...
The photochemical behaviors of chiral pollutants in aqueous solutions are rarely studied using chiral monomers, which may hamper their precise risk assessment and lead to suspicious conclusions. In this study, we systematically investigated the phototransformation behavior and toxicity evolution of two widely used chiral pesticides (triadimefon (TF) and triadimenol (TN)) at enantiomer and diastereomer levels, and proposed a calculation method of total photolysis rate constants of chiral mixture. Results show that TF and TN could be photodegraded faster in pure water than in natural waters, and the observed photolysis rate constants (k) of TN with two chiral centers exhibit enantioselectivity, i.e., k(TN-RS) = k(TN-SR) > k(TN-RR) = k(TN-SS). The photolysis of TF and TN mainly occurs through their excited singlet and triplet states, respectively. Their photodegradation pathways mainly include dechlorination and elimination of triazole ring. TF could also undergo ether bond cleavage. It is also found that, both TF and TN exhibit photo-induced toxicity to V. fischeri, due to the generation of more toxic products than parent compounds. Furthermore, TN exhibits enantioselective photo-induced toxicity after 240-min irradiation, which could be ascribed to the formation of chiral products. These results could benefit the understanding of enantioselective environmental behavior of chiral pollutants.
Topics: Pesticides; Environmental Pollutants; Photolysis; Stereoisomerism; Water; Water Pollutants, Chemical; Kinetics
PubMed: 37276764
DOI: 10.1016/j.envint.2023.107996 -
Nature Communications Dec 2023Prodrug photolysis enables spatiotemporal control of drug release at the desired lesions. For photoactivated therapy, near-infrared (NIR) light is preferable due to its...
Prodrug photolysis enables spatiotemporal control of drug release at the desired lesions. For photoactivated therapy, near-infrared (NIR) light is preferable due to its deep tissue penetration and low phototoxicity. However, most of the photocleavable groups cannot be directly activated by NIR light. Here, we report a upconversion-like process via only one step of energy transfer for NIR light-triggered prodrug photolysis. We utilize a photosensitizer (PS) that can be activated via singlet-triplet (S-T) absorption and achieve photolysis of boron-dipyrromethene (BODIPY)-based prodrugs via triplet-triplet energy transfer. Using the strategy, NIR light can achieve green light-responsive photolysis with a single-photon process. A wide range of drugs and bioactive molecules are designed and demonstrated to be released under low-irradiance NIR light (100 mW/cm, 5 min) with high yields (up to 87%). Moreover, a micellar nanosystem encapsulating both PS and prodrug is developed to demonstrate the practicality of our strategy in normoxia aqueous environment for cancer therapy. This study may advance the development of photocleavable prodrugs and photoresponsive drug delivery systems for photo-activated therapy.
Topics: Prodrugs; Photolysis; Drug Delivery Systems; Photosensitizing Agents; Energy Transfer
PubMed: 38062051
DOI: 10.1038/s41467-023-43805-y