High-concentration nitrite-containing wastewater that presents extreme toxicity to human health and organisms is difficult to be treated using traditional biological process.In this study,a novel microwave-enhanced ch...High-concentration nitrite-containing wastewater that presents extreme toxicity to human health and organisms is difficult to be treated using traditional biological process.In this study,a novel microwave-enhanced chemical reduction process(MECRP)using sulfarninic acid(SA)was proposed as a new manner to treat such type of wastewater.Based on lab-scale experiments,it was shown that 75%-80%nitrite(NO2-)could be removed within time as short as 4 min under 50 W microwave irradiation in pH range 5-10 when molar ratio of SA to nitrite(SA/NO2-)was 0.8.Pilot-scale investigations demonstrated that MECRP was able to achieve nitrite and chemical oxygen demand(COD)removal with efficiency up to 80%and 20%,respectively under operating conditions of SA concentration 80 kg/m3,SA/NO2-ratio 0.8,microwave power 3.4 kW,and stirring time 3 min.Five-day biological oxygen demand(BODs)/COD value of treated effluent after MECRP was increased from 0.05 to 0.36(by 620%),which clearly suggested a considerable improvement of biodegradability for subsequent biological treatment.This study provided a demonstration of using microwave irradiation to enhance reaction between SA and nitrite in a short time,in which nitrite in wastewater was completely converted into nitrogen gas without leaving any sludge and secondary pollutants.展开更多
Microwave-enhanced laser-induced breakdown spectroscopy(ME-LIBS)is a promising analysis technique for trace element detection with the advantage of high signal intensity.However,the shot-to-shot repeatability of the M...Microwave-enhanced laser-induced breakdown spectroscopy(ME-LIBS)is a promising analysis technique for trace element detection with the advantage of high signal intensity.However,the shot-to-shot repeatability of the ME-LIBS signal is relatively low,which affects the precision of the result and limits quantification performance.A cavity confinement microwave-enhanced laser-induced plasma(CC-ME-LIP)modulation method is proposed to improve the repeatability of the ME-LIBS signal.During the plasma evolution,cavity confinement provides an environment that regulates plasma around the microwave probe,controls plasma expansion,and minimizes interaction with the atmosphere.This behavior enhances the stability of the plasma morphology,leading to improved signal repeatability.In addition,confinement increases the energy transfer process within the plasma by the superimposition of two methods,resulting in a stronger signal intensity.The CC-ME-LIP modulation method is applied to the brass sample.The relative standard deviation(RSD)of the different copper and zinc lines has been reduced,along with an improvement of the intensity enhancement factor(IEF).For example,Cu 521.820 nm line RSD reduced from 29.11%(ME-LIBS)to 17.12%(CC-MELIBS)with an IEF of 1.08.The result demonstrated that the proposed approach significantly improves the repeatability of the ME-LIBS signal,thereby increasing the overall signal quality.To gain a deeper understanding,a detailed analysis of the mechanisms behind the increased signal intensity and improved repeatability was further investigated.展开更多
基金supported by the National Natural Science Foundation of China(No.50678045)
文摘High-concentration nitrite-containing wastewater that presents extreme toxicity to human health and organisms is difficult to be treated using traditional biological process.In this study,a novel microwave-enhanced chemical reduction process(MECRP)using sulfarninic acid(SA)was proposed as a new manner to treat such type of wastewater.Based on lab-scale experiments,it was shown that 75%-80%nitrite(NO2-)could be removed within time as short as 4 min under 50 W microwave irradiation in pH range 5-10 when molar ratio of SA to nitrite(SA/NO2-)was 0.8.Pilot-scale investigations demonstrated that MECRP was able to achieve nitrite and chemical oxygen demand(COD)removal with efficiency up to 80%and 20%,respectively under operating conditions of SA concentration 80 kg/m3,SA/NO2-ratio 0.8,microwave power 3.4 kW,and stirring time 3 min.Five-day biological oxygen demand(BODs)/COD value of treated effluent after MECRP was increased from 0.05 to 0.36(by 620%),which clearly suggested a considerable improvement of biodegradability for subsequent biological treatment.This study provided a demonstration of using microwave irradiation to enhance reaction between SA and nitrite in a short time,in which nitrite in wastewater was completely converted into nitrogen gas without leaving any sludge and secondary pollutants.
基金the financial support from the National Key Research and Development Program of China(No.2023YFB4102900)the Carbon Neutrality and Energy System Transformation(CNEST)Program led by Tsinghua UniversityHuaneng Group Science and Technology Research Project(No.HNKJ22-H105).
文摘Microwave-enhanced laser-induced breakdown spectroscopy(ME-LIBS)is a promising analysis technique for trace element detection with the advantage of high signal intensity.However,the shot-to-shot repeatability of the ME-LIBS signal is relatively low,which affects the precision of the result and limits quantification performance.A cavity confinement microwave-enhanced laser-induced plasma(CC-ME-LIP)modulation method is proposed to improve the repeatability of the ME-LIBS signal.During the plasma evolution,cavity confinement provides an environment that regulates plasma around the microwave probe,controls plasma expansion,and minimizes interaction with the atmosphere.This behavior enhances the stability of the plasma morphology,leading to improved signal repeatability.In addition,confinement increases the energy transfer process within the plasma by the superimposition of two methods,resulting in a stronger signal intensity.The CC-ME-LIP modulation method is applied to the brass sample.The relative standard deviation(RSD)of the different copper and zinc lines has been reduced,along with an improvement of the intensity enhancement factor(IEF).For example,Cu 521.820 nm line RSD reduced from 29.11%(ME-LIBS)to 17.12%(CC-MELIBS)with an IEF of 1.08.The result demonstrated that the proposed approach significantly improves the repeatability of the ME-LIBS signal,thereby increasing the overall signal quality.To gain a deeper understanding,a detailed analysis of the mechanisms behind the increased signal intensity and improved repeatability was further investigated.
