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Comparison of acetaminophen degradation in UV-LED-based advance oxidation processes: Reaction kinetics, radicals contribution, degradation pathways and acute toxicity assessment
摘要： Ultraviolet light emitting diode (UV-LED)-based advanced oxidation processes (AOPs) including UV-LED/chloramine (UV-LED/NH2Cl), UV-LED/hydrogen peroxide (UV-LED/H2O2) and UV-LED/persulfate (UV-LED/PS), were adopted for acetaminophen (AAP) removal. Results showed that AAP could be effectively degraded by the hybrid processes compared to solely using with UV irradiation and oxidants. The AAP degradation in the three UV-LED-based AOPs were in the order of UV-LED/PS N UV-LED/H2O2 N UV-LED/NH2Cl and followed a pseudo-?rst-order kinetics. The degradation rate constant (kobs) increased with increasing oxidant dosage, whereas overdosing lowered the AAP degradation. The second-order rate constants of HO?, SO4??, and Cl? with AAP were calculated as 5.15 × 109, 7.66 × 109 and 1.08 × 1010 M?1 s?1, respectively. Under neutral conditions, the contributions of UV-LED, HO?, and Cl? to AAP degradation were 4.21%, 60.15% and 35.64% in the UV-LED/NH2Cl system, whereas the respective contributions of UV-LED, HO? and SO4?? to AAP degradation were 2.09%, 22.84% and 75.07% in UV-LED/PS system, respectively. Meanwhile, the corresponding contributions of the involved reactive species were found to be pH-dependence. The natural organic materials (NOM) inhibited the ? had different effects on AAP degradation in the ?, and NO3 AAP degradation, and the presence of Cl?, HCO3 three hybrid processes. The AAP degradation was signi?cantly inhibited in the three UV-LED-based AOPs in real water. In addition, the intermediate products were also identi?ed, and possible degradation pathways were proposed in the three UV-LED-based AOPs. The acute toxicity bioassay using bacterium Vibrio ?scheri suggested that the UV-LED/PS process was more effective than the UV-LED/H2O2 and UV-LED/NH2Cl processes in reducing the acute toxicity of the reacted AAP solution. Among the three UV-LED-based AOPs, the UV-LED/PS was found to be the most ef?cient process for AAP degradation.
关键词： Acute toxicity,Rate constants,UV-LED-based AOPs,Degradation pathways,Acetaminophen
更新于2025-09-23 15:21:01
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Kinetic and Mechanistic Investigation of the Photocatalyzed Surface Reduction of 4-Nitrothiophenol Observed on a Silver Plasmonic Film via Surface-Enhanced Raman Scattering
摘要： Hot electrons generated by photo-induced plasmon decay from plasmonic metal surface can reduce 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP). Comparing to the reduction with a reducing agent such as sodium borohydride, Surface-Enhanced Raman scattering (SERS) measurements were performed here to elucidate the complex molecular mechanism of the reduction in presence of halide ions and hydrogen ions. The SERS measurements were performed using a simply prepared silver plasmonic film (AgPF), which enables monitoring of the reaction in different conditions at a solid-liquid surface, and eliminates the need for use of a reducing agent. As the concentration of H+ and Cl- could controlled, the observation of the reaction under a systematic set of condition was possible. Based on the kinetic traces of the intermediates, a reaction mechanism for the 4-NTP to 4-ATP reduction is suggested. Rate constants for the individual reactions are presented that fit the measured kinetic traces, and the role of hydrogen in each reaction step is characterized. This work provides clarification on the molecular transformation directly using protons as hydrogen source and demonstrates an effective method of applying a simple and low-cost silver surface catalyst for SERS studies. Moreover, the monitoring of Cl--concentration-dependent spectra gained insight into the hot-electron conversion process during the photoreduction and strongly support the formation of AgCl for activation of H+.
关键词： in-situ SERS spectra,kinetic rate constants,reaction mechanism,time-resolved measurements,selective surface photocatalytic reaction
更新于2025-09-23 15:19:57
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[Springer Theses] The Electronic Transitions of Molecular Oxygen || Solvent Effects on the O2(a1?g) → O2(b1$$\Sigma_{\text{g}}^{ + }$$) Transition
摘要： In this chapter, we have presented O2(a1Δg) → O2(b1Σ+g) absorption spectra and extinction coefficients for oxygen in 16 solvents. Through the Strickler-Berg equation, these data were converted into the corresponding O2(b1Σ+g) → O2(a1Δg) radiative rate constants to give the first comprehensive set of data on the probability of the O2(b1Σ+g) → O2(a1Δg) transition in solution. With these data in hand, energies and transition probabilities of all three electronic transitions in oxygen have been quantified in a wide range of solvents. We find that our data is consistent with the theoretical framework put forth by Minaev. Nevertheless, our data also suggest that the interaction between oxygen and the solvent takes place through different mechanisms that are simultaneously acting to perturb each of the electronic transitions in oxygen in different ways. In our mind, the system must now be subjected to more systematic and extensive theoretical investigations, in order to quantitatively rationalize these experimental observations.
关键词： Minaev’s theory,radiative rate constants,O2(a1Δg) → O2(b1Σ+g) transition,Strickler-Berg equation,solvent effects
更新于2025-09-23 15:19:57
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Tuning the Crystal Packing and Semiconductor Electronic Properties of 7,7’-Diazaisoindigo by Side-Chain Length and Halogenation
摘要： In the last years, the 7,7’-diazaisoindigo has emerged as a promising building block for semiconductor materials. In this work, we have studied different electronic properties which can be related to the semiconducting character of a family of 7,7’-diazaisoindigo derivatives. Concretely, we have analyzed the role of halogen substituents and different-length side chains on these properties calculated by means of the Density Functional Theory. In total, sixteen halogenated and non-halogenated diazaisoindigo derivatives were investigated. Four of these compounds were also synthetized and their X-ray structures were employed as starting points for the calculation of crystal structure of the rest of the novel compounds. In general, high electron transfer rate constants and electron mobilites were calculated for the studied 7,7’-diazaisoindigo derivatives, especially for bromine derivatives and compounds with long-side chains. The origin of these high rate constants mainly resides in the strong electronic couplings found for diazaisoindigo crystals in the π-stacking direction.
关键词： 7,7’-diazaisoindigo,side chains,electron mobilities,halogen substituents,Density Functional Theory,semiconductor materials,electron transfer rate constants,π-stacking direction
更新于2025-09-04 15:30:14