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•The mechanism of ofloxacin degradation by heat-activated persulfate were investigated.•Ofloxacin degradation in the system fitted well with the pseudo-first-order reaction model.•The ...four degradation pathways of ofloxacin were proposed.•The toxicity of ofloxacin and its intermediates was predicted.
The widespread occurrence of fluoroquinolone antibiotics, such as ofloxacin (OFX), in natural water and soil has received increasing attention in terms of their potentially dangerous impacts on public health and ecosystems. In this study, the kinetics and mechanisms of OFX degradation by heat-activated persulfate (HAP) was investigated. Results showed that OFX degradation could be achieved effectively and fitted well with the pseudo-first-order reaction model in the HAP system. The OFX degradation efficiency was dramatically enhanced with increased temperature and initial persulfate dosage and inhibited in the presence of the common coexisting water matrices (e.g., bicarbonate, chloride, and humic acid). Quenching tests and electron paramagnetic resonance studies demonstrated the simultaneous contribution of both radicals with sulfate radicals having a slightly higher effect than hydroxyl radicals in the degradation process of OFX. Various intermediates of OFX degradation were characterized using High-performance liquid chromatography-Mass spectrometry (HPLC-MS), and detailed degradation pathways of OFX were proposed. And the toxicity of OFX and its intermediate products was predicted using the Ecological Structure-Activity Relationships (ECOSAR) and Toxicity Estimation Software Tools (TEST).
Magnetic Fe3O4@BiOI@AgI (FBA) spheres were synthesized through a multi-step process. The fabricated photocatalysts were characterized by different techniques. To testify the visible light driven ...photocatalytic activity of FBA, Rhodamine B and Bisphenol A were chosen as model common and emerging organic contaminants, respectively. While, gram-negative strain Escherichia coli was selected as model waterborne bacteria. The results showed that under visible light irradiation, FBA contained strong photocatalytic degradation capacity towards both RhB and BPA. Moreover, FBA was also found to exhibit excellent disinfection activity towards E. coli. The photocatalytic mechanisms for different pollutants by FBA were determined and found to vary for different pollutants. Specifically, scavenger experiments, degradation intermediates determination, as well as theoretical density functional theory (DFT) analysis showed that RhB and BPA were degraded via photosensitization (dominated by e- and ·O2−) and direct photocatalytic oxidation (contributed by h+, e- and ·O2−), respectively. Whereas, E. coli cells yet were found to be inactivated by the generation of e- and ·O2− rather than by the released Ag+. Since it contained superparamagnetic property, FBA could be easily separated from the reaction suspension after use. Due to the excellent photo stability, FBA exhibited strong photocatalytic activity in the fourth reused recycle. Therefore, FBA could serve as a promising alternative for water purification.
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•Facile synthesis of Fe3O4@BiOI@AgI hybrid photocatalyst.•Excellent visible light driven activity towards RhB, BPA and E. coli cells.•Different photocatalytic mechanisms for different pollutants.•Magnetic recycle and good photo stability.•DFT calculation elucidates the degradation pathways of RhB and BPA.
This article presents a review of drying processes of fruits and vegetables in which vitamin C degradation was considered. Vitamin C is an important and essential nutrient for humans and it can be ...taken as an index of nutrient quality of processes. Many researchers have reported the effect of different drying methods and the influence of drying conditions on the vitamin C content. In addition, the effect of other parameters related to the sample structure or to pretreatments on the final quality of the dried product is discussed. Vitamin C degradation mechanisms proposed in the literature, models applied to describe its kinetics, and recent advances in drying processes aiming high retention of this nutrient are also provided.
The origin of the dissolution of methylammonium lead trihalide (MAPI) crystals in liquid water is clarified by finite-temperature molecular dynamics by developing a MYP-based force field (MYP1) for ...water–MAPI systems. A thermally activated process is found with an energy barrier of 0.36 eV consisting of a layer-by-layer degradation with generation of inorganic PbI2 films and solvation of MA and I ions. We rationalize the effect of water on MAPI by identifying a transition from a reversible absorption and diffusion in the presence of vapor to the irreversible destruction of the crystal lattice in liquid due to a cooperative action of water molecules. A strong water–MAPI interaction is found with a binding energy of 0.41 eV/H2O and wetting energy of 0.23 N/m. The water vapor absorption is energetically favored (0.29 eV/H2O), and the infiltrated molecules can migrate within the crystal with a diffusion coefficient D = 1.7 × 10–8 cm2/s and activation energy of 0.28 eV.
High levels of toxic organic pollutants commonly detected during domestic/industrial wastewater treatment have been attracting research attention globally because they seriously threaten human ...health. Sulfate-radical-based advanced oxidation processes (SR-AOPs) have been successfully used in wastewater treatment, such as that containing antibiotics, pesticides, and persistent organic pollutants, for refractory contaminant degradation. This review summarizes activation methods, including physical, chemical, and other coupling approaches, for efficient generation of sulfate radicals and evaluates their applications and economic feasibility. The degradation behavior as well as the efficiency of the generated sulfate radicals of typical domestic and industrial wastewater treatment is investigated. The categories and characteristics of the intermediates are also evaluated. The role of sulfate radicals, their kinetic characteristics, and possible mechanisms for organic elimination are assessed. In the last section, current difficulties and future perspectives of SR-AOPs for wastewater treatment are summarized.
•Focus on the preparation and electrochemical property of BDD film electrode.•Insight into the electrocatalytic process and mechanism on BDD electrodes towards pollutants.•The enhancement approaches ...towards electrochemical oxidation kinetics are included.•Other combination technologies based on electrochemical oxidation on BDD electrode are also described.•Perspectives and outlooks for BDD electrodes in electrochemical oxidation.
Boron-doped diamond (BDD) electrode has been considered as an optimal electrode material for electrochemical oxidation of organic contaminants in the aquatic environment due to its good physical and chemical properties. The fundamental research and practical application of BDD electrode in the mineralization of organic pollutants have been well developed up to now. In this review, the preparation and electrochemical properties of BDD film electrode are focused first. Then, we investigate the electrocatalytic process and degradation mechanisms on BDD electrodes based on the electrochemical oxidation of refractory pollutants in recent years. The enhancement approaches towards electrochemical oxidation kinetics are further highlighted, which include the establishment of high activity BDD electrodes and enhancement of mass transfer process during the electrochemical oxidation. Other combination technologies based on electrochemical oxidation with BDD electrode are also described to expand the application of BDD electrode in wastewater treatment. Further, the opportunity and prospective of BDD electrode are forecasted according to the existing problems in wastewater treatment.
The Cover Feature shows that hydroxyl‐radical‐initiated degradation and transformation of methyl and ethyl iodides are crucial in the iodine chemical cycle in the marine boundary layer. Their ...atmospheric degradation would produce atomic iodine, which leads to ozone layer depletion. Cover design by Feng‐Yang Bai, Jia‐Ming Sun and Co‐workers. More information can be found in the Research Article by Feng‐Yang Bai, Shuang Ni, Zhen Zhao and co‐workers.
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•A trace Ti3+ and N-codoped TiO2 nanotube array anode is fabricated successfully.•The electrochemical performance could be improved by reduction and N doping.•LSV revealed that the ...introduction of trace N is conducive to the increase of OEP.•The degradation processes follow an apparent first-order kinetic model.•The removal efficiency, COD removal rate and TOC removal rate could be improved.
A trace Ti3+- and N-codoped TiO2 nanotube array (TiON) anode is fabricated by electrochemical reduction after introducing nitrogen into the TiON. The TiON anode material is characterized by scanning electron microscopy, X-ray diffraction, Raman spectra and X-ray photoelectron spectroscopy. Electrochemical analyses of TiON, including cyclic voltammetry, electrochemical impedance spectroscopy and linear scan voltammetry, are conducted to confirm that the electrochemical performance could be significantly improved by electrochemical reduction and N doping. The achieved TiON anode is applied to the electrocatalytic oxidation of tetracycline (TC) and metronidazole (MNZ). The effect of applied current density, initial solution pH and initial TC/MNZ concentration on the reaction kinetics is systematically evaluated to obtain the optimal conditions. The degradation processes follow an apparent first-order kinetic model in all conditions. After 240 min of reaction time, the TC removal efficiency, chemical oxygen demand (COD) removal rate and total organic carbon (TOC) removal rate are >99%, 92.86% and 74.98%, respectively. The MNZ removal efficiency, COD and TOC removal rate achieved are >99%, 93.03% and 79.30%, respectively, after 240 min of degradation. The excellent removal efficiency of TC and MNZ indicates that this TiON anode is a promising material in the practical application of removing antibiotics from water.
Astaxanthin is a pigment from the carotenoid group found in algae, shrimp, and crabs. Due to its chemical structure, astaxanthin has many health benefits but low stability against direct exposure to ...light and oxygen. In this study, the Zn-astaxanthin complex was synthesized using a reflux reactor at 37o and 60oC. Complex compounds were analyzed using a UV-Vis spectrophotometer and FTIR. The UV-Vis spectrophotometer analysis showed a bathochromic shift in acetone (475 to 477 nm). In comparison, in dimethyl sulfoxide, a hypsochromic shift (493 to 475 nm) was observed, and a new absorption peak was observed at 330 nm. FTIR analysis shows a decrease in the intensity of the C=O stretching vibration and -OH group vibration at 1712 and 1219 cm-1, respectively. This indicated an interaction between the metal ion Zn2+ and astaxanthin. Zn-astaxanthin has better stability than astaxanthin during irradiation, using a halogen lamp at a light intensity of 300 W/m2 for 6 hours. Based on the zero-order degradation kinetics model, the degradation rate constant of the Zn-astaxanthin complex was 0.0621, smaller than that of astaxanthin (0.0880).
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•Bi-Sn-Sb/γ-Al2O3 particle electrode is prepared by impregnation method.•Tetracycline removal rate is significantly influenced by preparation conditions.•Intermediates and possible ...pathway of Tetracycline by three-dimensional reactor are identified.•Bi-Sn-Sb/γ-Al2O3 particle electrode shows excellent electrocatalytic oxidation capacity.
In this work, highly efficient Bi-Sn-Sb/γ-Al2O3 particle electrodes were prepared for effectively degrading tetracycline. The effects of a mass ratio (Sn: Sb), the mass ration of Bi:(Sn + Sb), impregnation times, calcination temperature, and calcination time on the electrocatalytic oxidation capacity of Bi-Sn-Sb/γ-Al2O3 particle electrode was investigated. Conditions in which mass ratio of (Sn: Sb) = 10:1, the mass ratio of Bi:(Sn/Sb) = 1:1, impregnation times 2 h, calcination temperature 500 °C., and calcination time 3 h were considered as optimal preparation conditions for Bi-Sn-Sb/γ-Al2O3 particle electrode. It was cherecterized by infrared spectroscopy (IR), scanning electron microscope (SEM), energy dispersive X-ray detector (EDX), X-Ray Diffraction (XRD), and X-ray fluorescence (XRF) techniques to conforming that the triclinic Bi2O3 formed in the preparation conditions has superior electrocatalytic activity. The electrocatalytic oxidation mechanism of tetracycline by Bi-Sn-Sb/γ-Al2O3 particle electrode is proposed by determining degradation intermediates through LC–MS detection. Electrocatalytic oxidation experiments by adding tert-butyl alcohol indicate that the formation of OH is the primary responsibility for degradating tetracycline. Electrocatalytic degradation of tetracycline at different initial concentration shows that the degradation of tetracycline meets the pseudo first-order kinetics. Results suggest that the three-dimensional electrochemical reactor with Bi-Sn-Sb/γ-Al2O3 particle electrodes could be an alternative for the pretreatment of antibiotic wastewater before biological treatment.
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