Single flow treatment degradation of antibiotics in water using falling-film dielectric barrier discharge

The environmental contamination caused by antibiotics is increasingly conspicuous due to their widespread manufacture and misuse. Plasma has been employed in recent years for the remediation of antibiotic pollution in the environment. In this work, a falling-film dielectric barrier discharge was used to degrade the antibiotic tetracycline(TC) in water. The reactor combined the gas-liquid discharge and active gas bubbling to improve the TC degradation performance. The discharge characteristics, chemical species’ concentration, and degradation rates at different parameters were systematically studied. Under the optimized conditions(working gas was pure oxygen, liquid flow rate was 100 mL/min, gas flow rate was 1 L/min,voltage was 20 kV, single treatment), TC was removed beyond 70% in a single flow treatment with an energy efficiency of 145 mg/(kW·h). The reactor design facilitated gas and liquid flow in the plasma area to produce more ozone in bubbles after a single flow under pure oxygen conditions, affording fast TC degradation. Furthermore, long-term stationary experiment indicated that long-lived active species can sustain the degradation of TC. Compared with other plasma treatment systems, this work offers a fast and efficient degradation method, showing significant potential in practical industrial applications.

Editorial:The development of eco-friendly insulating gases and SF6-free equipment for‘net-zero’

Developing low-carbon gas insulated transmission and distribution equipment is essential to achieve the‘carbon peak,carbon neutralisation’or‘net-zero’in the power industry.Scholars have carried out various research on the eco-friendly insulating gas(such as C4F7N,C5F10O)and next-generation SF6-free equipment to gradually reduce the utilisation of strong greenhouse gas SF6.

Assessment on gas-polyethylene terephthalate solid interface partial discharge properties of C4F7N/CO_(2)gas mixture for eco-friendly gas insulating transformer

The eco-friendly insulating gas perfluoroisobutyronitrile(C_(4)F_(7)N)is potentially used in gas-insulated transformers(GIT)to replace sulphur hexafluoride(SF_(6)).However,evaluation of the long-term insulation reliability and gas–solid interface discharge decomposition characteristics of the gas–solid film insulation structure in GIT is indispensable.The authors simulated the gas–solid film insulation structure in GIT and explored the interface partial discharge(PD)characteristics of C4F7N/CO_(2)gas mixture with polyethylene terephthalate(PET).The effect of gas pressure,mixing ratio on gas–solid interface gas decomposition,PET degradation was investigated,and the interaction mechanism was analysed.It is found that the interface PD generated three degradation regions on a PET film.The gas–solid interface reaction in the electrode contact region and the discharge development trace was significantly higher than that of halation region.The content of gas decomposition products decreases with the increase of gas pressure and the PD intensity of SF6-PET is inferior to that of C_(4)F_(7)N/CO_(2)under the same condition.Relevant results provide reference for the development and application of C_(4)F_(7)N/CO_(2)based GIT.

Numerical and Experimental Study on Performance of a Low-Backpressure Polyhedral Thermoelectric Generator for Waste Heat Recovery

Optimized fin arrangement and dimension of heat exchanger can improve the maximum output power of thermoelectric generator(TEG)system which converts the wasted heat into electricity with thermoelectric modules(TEMs).Considering that the geometric symmetry contributes to the temperature uniformity improvement and convenient TEMs arrangement,a low-backpressure TEG system based on a polyhedral-shape heat exchanger was developed.To assess the effect of inner topology and fin parameters on the heat transfer and output power of the TEG system,a realizable k-?turbulence based numerical model was established and validated to perform numerical simulations.The results demonstrate that increasing fin length,fin width and fin intersection angle are beneficial to the average surface temperature,temperature distribution uniformity and maximum output power of the TEG system.Moreover,decreasing fin spacing distance contributes to the enhanced average surface temperature and maximum power of TEG system,and has insignificant effect on its temperature uniformity.The inserted fins with optimal length,width,intersection angle and spacing distance enhance higher output power,whereas result in increasing backpressure.The maximum difference between the experimental and simulation results is 3.2%,which validates the feasibility of the established numerical model.It also provides a theoretical reference to the optimal design and performance analysis of low-backpressure TEG systems used in automobile exhaust heat recovery.

Adsorption properties of environmentally friendly insulating medium C_(4)F_(7)N and its common decomposition products in NaA,NaZSM-5,and NaX molecular sieves

Selecting suitable materials to adsorb the C_(4)F_(7)N mixtures decomposition products could not only keep the stable operation of the environmentally friendly insulating gas switch cabinet,but also ensure the safety of operation and maintenance personnel.It is necessary to study the interaction of three types of molecular sieves with the C_(4)F_(7)N mixture and its decomposition products,which could provide a theoretical basis for the selection of adsorbents in the C_(4)F_(7)N gas switch cabinet.In this research,the molecular dynamics simulation was used to study the C_(4)F_(7)N-CO_(2)mixture and its ten kinds of decomposition products CO,CF_(4),C_(2)F_(6),C_(3)F_(6),C_(3)F_(8),CF_(3)H,CF_(3)CN,C_(2)F_(5)CN,C_(2)N_(2),and COF_(2)in three molecular sieves adsorption process(NaA,NaZSM-5,and NaX).The gas concentration distribution curve and interaction energy parameters were obtained by simulation.The interaction energies of C_(3)F_(8)in NaA,C_(4)F_(7)N in NaZSM-5,and C_(3)F_(6)in NaX molecular sieve are the largest,which are−368.35 kJ/mol,−174.93 kJ/mol,and−340.09 kJ/mol respectively.Then,the theoretical results were verified by the fluorocarbon gases adsorption experiment.The adsorption performance of three molecular sieves for all gases was obtained by combining the experimental results and dynamics parameters.The adsorption rate of the NaA molecular sieve for fluorocarbon gas is less than 35%,and its adsorption performance for all gases is weak.NaZSM-5 and NaX molecular sieves show excellent adsorption performance for C_(3)F_(6)and C_(3)F_(8),and the adsorption rates are over 70%.NaZSM-5 molecular sieve shows good adsorption capacity for CF_(3)CN,C_(2)F_(6),C_(2)N_(2),C_(3)F_(6),C_(3)F_(8),C_(4)F_(7)N,and C_(2)F_(5)CN.NaX molecular sieve shows good adsorption capacity for C_(3)F_(6),C_(3)F_(8),C_(4)F_(7)N,and C_(2)F_(5)CN.Both of them have the potential to be used as adsorbents in environmental protection insulated gas switch cabinet.

Arc decomposition behavior of C_(4)F_(7)N/Air gas mixture and biosafety evaluation of its by-products

At present,reports on the arc interruption and decomposition behavior of a C_(4)F_(7)N/air gas mixture especially the biosafety of its by-products are limited.Herein,a 57%C_(4)F_(7)N/43%air gas mixture was employed as an arc-quenching medium to conduct 200 breaking tests on a load switch(630 A/24 kV).The arc interruption and decomposition behavior of the gas mixture were evaluated,and the biosafety of the decomposition products was assessed based on an acute inhalation toxicity test.It was found that the average arcing time of the 200 breakings was about 10.1 ms and that breakings were basically completed at the zero-crossing of the second or third current half-cycle.The gas mixture after breaking decomposed dramatically(the C_(4)F_(7)N content decreased by 75.6%),generating a large number of gaseous by-products(CO,CF_(4),C_(2)F_(6),C_(3)F_(8),CF_(3)CN,C_(4)F_(8),CO_(2),C_(4)F_(10)N_(2),C_(3)F_(6),C_(2)N_(2),etc.)as well as solid by-products(carbon particles).The lethal concentration of 50%(LC50,4 h)of C_(4)F_(7)N/air after 200 breakings was 31 ppm(male mice)and 34 ppm(female mice),respectively,and the toxicity was classified as Grade 1.In general,C_(4)F_(7)N has an arc interruption capability,albeit weaker than that of SF_(6)under the same conditions.After breaking,the C_(4)F_(7)N gas mixture has a relatively high acute inhalation toxicity,and relevant safety protection measures for research or operation personnel are strictly needed.