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Connections between the molecular structures and their photochemical properties are highlighted and serve as guiding principles for designing indigos to be The critical impacts of pyrochar during 2,4,6-trichlorophenol photochemical remediation process: Cooperation between persistent free radicals and oxygenated The widespread use of polychlorophenols poses enormous environmental challenges
Biochar has the potential to accelerate the transformation of polychlorophenols. But the biochar-triggered photochemical decomposition mechanism of polychlorophenols still remains unclear. Herein, the photochemical behavior of pyrochar was comprehensively investigated in 2,4,6-trichlorophenol (TCP) remediation. Researches revealed that persistent free radicals (PFRs) and oxygenated functional groups (OFGs) on the surface of pyrochar cooperatively promoted ROS generation for TCP degradation. PFRs performed a key role of electron-donating and energy transfer in ROS conversion, especially in the activation of H2O2 into •OH. The hydroxyl groups of photosensitive components of pyrochar were photo-excited and provided electrons for enhanced ROS formation as well.

With photogenerated ROS involved, more TCP was decomposed through dechlorination under light irradiation than that in the dark, in which 1O2, •OH, and •O2- were the dominant active species. During this process, stronger light intensities (3 W/m2) and shorter light wavelengths (400 nm) can provide more energy for the activation of PFRs and OFGs, promoting the decomposition of TCP. This work casts a new light on the environmental roles of pyrochar in the photochemical removal of polychlorophenol pollutants.declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this Computational study of the mechanism of the photochemical and thermal ring-opening/closure reactions and solvent dependence in spirooxazines.Marcel·lí Domingo s/n, Tarragona-43007, Spain.The spirooxazine/merocyanine couple constitutes a photochromic system that can change from the colorless spirooxazine to the intensely colored merocyanine by thermal or photochemical activation by a reaction that opens the spiro ring of the oxazine. The mechanisms of the ring-opening/closure reactions that interconnect these two isomers have been elucidated by means of a computational study.

First, we have used the CASSCF/CASPT2 method to determine in detail these mechanisms in the gas phase for a small model that contains the photoactive part of the whole system. We have found that the state of spirooxazine excited by the initial absorption changes gradually to a lower excited state that is involved in a conical intersection that connects it with the ground state of merocyanine. The same conical intersection is involved in the backward photochemical reaction. Second, using a larger model that includes all the heteroatoms of the system and using the DFT (B3LYP) method, we have studied the influence of a solvent environment on the thermal equilibrium between the open and the closed species. It has been observed experimentally that the thermal equilibrium between these forms is practically unaltered by polar aprotic solvents, but it can be displaced toward the colored form in mixtures of polar protic and aprotic solvents, even if the first one is found in a very small proportion. To reproduce the experimental environments, we have taken into account the long-range effect of the polar aprotic solvent considering it a polarizable continuum, as done in the PCM method, and the short-range effect of the protic solvent including some explicit water molecules in the cluster studied at the atomic level. The results obtained are in good agreement with the experimental observations and explain the reason for this peculiar behavior.

Advanced oxidation treatment and photochemical fate of selected antidepressant pharmaceuticals in solutions of Suwannee River humic acid.Engineering, University of California, Irvine, Irvine, CA 92697-2175, USA. Antidepressant pharmaceuticals have recently been detected at low concentrations in wastewater and surface water. Seebio UV-Activated Acid Generator reports studies of the direct and indirect photochemical fate and treatment by advanced oxidation of three antidepressant compounds (duloxetine, venlafaxine and bupropion) in solutions of humic acid in order to elucidate their behavior in the natural environment prior to reaching a water treatment facility and potentially entering a potable water supply. Humic acid solution was prepared by adding to distilled water a known amount of organic matter as a photosensitizer. Learn more react very rapidly with hydroxyl radicals (·OH) and hydrated electrons (e(-)(aq)) with measured and used with the second order rate constants to show that the hydroxyl radical was an order of magnitude more effective than the singlet oxygen in the solar-induced photochemical degradation of the antidepressants. Excited state dissolved organic matter also accounted for a substantial portion of degradation of duloxetine, decreasing its half-life by 27% under solar irradiation.

Several reaction pathways and by-products arising from the photodegradation were identified using gamma-irradiation followed by LC-MS analysis.
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