Search

Your search keyword '"Li, Mengkai"' showing total 259 results
Start Over Author "Li, Mengkai"
259 results on '"Li, Mengkai"'

65. Degradation of micropolluants in flow-through VUV/UV/H2O2 reactors:Effects of H2O2 dosage and reactor internal diameter

Author

Zhan, Lumeng, Li, Wentao, Liu, Li, Han, Tao, Li, Mengkai, Qiang, Zhimin, Zhan, Lumeng, Li, Wentao, Liu, Li, Han, Tao, Li, Mengkai, and Qiang, Zhimin

Abstract

The degradation of atrazine (ATZ), sulfamethoxazole (SMX) and metoprolol (MET) in flow-through VUV/UV/H2O2 reactors was investigated with a focus on the effects of H2O2 dosage and reactor internal diameter (ID). Results showed that the micropollutants were degraded efficiently in the flow-through VUV/UV/H2O2 reactors following the pseudo first-order kinetics (R2 > 0.92). However, the steady-state assumption (SSA) kinetic model being vital in batch reactors was found invalid in flow-through reactors where fluid mixing was less sufficient. With the increase of H2O2 dosage, the ATZ removal efficiency remained almost constant while the SMX and MET removal was enhanced to different extents, which could be explained by the different reactivities of the pollutants towards HO•. A larger reactor ID resulted in lower degradation rate constants for all the three pollutants on account of the lower average fluence rate, but the change in energy efficiency was much more complicated. In reality, the electrical energy per order (EEO) of the investigated VUV/UV/H2O2 treatments ranged between 0.14–0.20, 0.07–0.14 and 0.09–0.26 kWh/m3/order for ATZ, SMX and MET, respectively, with the lowest EEO for each pollutant obtained under varied H2O2 dosages and reactor IDs. This study has demonstrated the efficiency of VUV/UV/H2O2 process for micropollutant removal and the inadequacy of the SSA model in flow-through reactors, and elaborated the influential mechanisms of H2O2 dosage and reactor ID on the reactor performances.

Published
2021

70. Multidentate Ligand Polyethylenimine Enables Bright Color-Saturated Blue Light-Emitting Diodes Based on CsPbBr3 Nanoplatelets

Author

Yin, Wenxu, primary, Li, Mengkai, additional, Dong, Wei, additional, Luo, Zhao, additional, Li, Yanxiu, additional, Qian, Jingyu, additional, Zhang, Jiaqi, additional, Zhang, Wei, additional, Zhang, Yu, additional, Kershaw, Stephen V., additional, Zhang, Xiaoyu, additional, Zheng, Weitao, additional, and Rogach, Andrey L., additional

Published
2021
Full Text
View/download PDF

72. VUV/UV light inducing accelerated phenol degradation with a low electric input† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6ra26043h Click here for additional data file

Author

Li, Mengkai, Wen, Dong, Qiang, Zhimin, and Kiwi, John

Subjects
Chemistry
Abstract

This study presents the kinetics and mechanism for the accelerated degradation of phenol in a mini-fluidic VUV/UV photoreaction system., This study presents the first evidence for the accelerated degradation of phenol by Fenton's reagent in a mini-fluidic VUV/UV photoreaction system (MVPS). A low-pressure mercury lamp used in the MVPS led to a complete degradation of phenol within 4–6 min. The HO˙ and HO2˙ originating from both Fenton's reagent and VUV photolysis of water were identified with suitable radical scavengers. The effects of initial concentrations of phenol, H2O2 and Fe3+ as well as solution pH on phenol degradation kinetics were examined. Increasing the initial phenol concentration slowed down the phenol degradation, whereas increasing the initial H2O2 or Fe3+ concentration accelerated the phenol degradation. The optimal solution pH was 3.7. At both 254 and 185 nm, increasing phenol concentration enhanced its absorption for the incident photons. The reaction mechanism for the degradation of phenol was suggested consistent with the results obtained. This study indicates that the VUV/UV photo-Fenton process has potential applications in the treatment of industrial wastewater containing phenol and related aromatic pollutants.

Published
2017

81. Electrical conductivity of thermally reduced graphene oxide/polymer composites with a segregated structure

Author

Li Mengkai, Hongliang Hu, Zhudi Zhao, and Chunxiao Gao

Subjects
chemistry.chemical_classification, Materials science, Graphene, Oxide, Percolation threshold, General Chemistry, Polymer, law.invention, chemistry.chemical_compound, chemistry, law, Electrical resistivity and conductivity, General Materials Science, Composite material, Fluoride, Electrical conductor, Graphene oxide paper
Abstract

A simple method to prepare thermally reduced graphene oxide/polymer composites was developed to enhance the electrical conductivity of the polymer. Graphene oxide sheets were coated onto the surfaces of poly(vinylidene fluoride) powders and then hot pressed at 200 °C to form composites with a segregated structure. After hot-pressing, the thermally reduced graphene oxide sheets were located in the interstices among the polymer domains and formed a two-dimensional conductive network. The resulting composites exhibited excellent electrical conductivity and a low percolation threshold (0.105 vol.%).

Published
2013

90. Micropollutant Degradation by the UV/H2O2Process: Kinetic Comparison among Various Radiation Sources

Author

Li, Mengkai, Li, Wentao, Wen, Dong, Bolton, James R., Blatchley, Ernest R., and Qiang, Zhimin

Abstract

Kinetic comparisons of micropollutant degradation by ultraviolet (UV) based advanced oxidation processes among various radiation sources are an important issue, yet this is still a challenge at present. This study investigated comparatively the kinetics of sulfamethazine (SMN) degradation by the UV/H2O2process among three representative radiation sources, including low-pressure mercury UV (LPUV, monochromatic), medium-pressure mercury UV (MPUV, polychromatic), and vacuum UV(VUV)/UV (dual wavelengths causing different reaction mechanisms) lamps. Experiments were conducted with a newly developed mini-fluidic MPUV photoreaction system and a previously developed mini-fluidic VUV/UV photoreaction system. Measured and modeled results both indicate that the photon fluence-based SMN degradation rate constant (kp′) followed a descending order of VUV/UV/H2O2> MPUV/H2O2(200–300 nm) > LPUV/H2O2, and the kp′of the MPUV lamp was dependent on the wavelength range selected for photon fluence calculation. Analysis of potential errors revealed that a shorter effective path-length could have a lower error, and the maximum errors for the MPUV/H2O2and LPUV/H2O2processes in this study were 7.7% and 18.2%, respectively. This study has developed a new method for kinetic comparisons of micropollutant degradation by UV-AOPs among various radiation sources at bench-scale, which provides useful reference to practical applications.

Published
2019
Full Text
View/download PDF

91. Organic Pollutant Degradation in Water by the Vacuum-Ultraviolet/Ultraviolet/H2O2Process: Inhibition and Enhancement Roles of H2O2

Author

Li, Mengkai, Li, Wentao, Bolton, James R., Blatchley, Ernest R., and Qiang, Zhimin

Abstract

A vacuum-ultraviolet/ultraviolet (VUV/UV) mercury lamp was found to be a highly efficient radiation source for UV-based advanced oxidation processes (AOPs). If this lamp could enhance the UV/H2O2process, it would be very attractive. Hence, we have investigated sulfamethazine (SMN) degradation by the VUV/UV/H2O2process based on a bench-scale mini-fluidic VUV/UV photoreaction system (MVPS), a pilot reactor, and a model analysis. At high [SMN]0in the MVPS, the apparent SMN degradation rate constant (k′app) increased with increasing H2O2dose, while at low [SMN]0, k′appdecreased with increasing H2O2dose; this behavior was unexpected. Meanwhile, at low [SMN]0in a pilot reactor, H2O2induced just a slight enhancement in the VUV/UV/H2O process. A numerical simulation of the process suggested that for an integrated AOP (i.e., VUV/UV/H2O2) consisting of various component AOPs, H2O2could inhibit the component AOPs with HO* that did not originate from H2O2(e.g., VUV photolysis of water). The apparent H2O2role in the integrated AOPs was dependent on the contribution comparison between component AOPs that involved HO* that did or did not originate from H2O2. These results revealed important information regarding the application of the VUV/UV/H2O2process in water treatment.

Published
2018
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results