低温等离子体降解污染土壤热脱附尾气中DDTs
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摘要
为优化低温等离子体技术对污染土壤热脱附尾气的处理效果,采用脉冲电晕放电等离子体处理含DDTs(滴滴涕)的热脱附尾气,控制进气中的ρ(DDTs)为2. 873 mg/m~3,考察了载气φ(O_2)、等离子体温度、载气湿度和脉冲电压对DDTs降解效果的影响,分析了O_3在降解过程中的作用.结果表明:(1)当氮气/氧气混合载气中φ(O_2)分别为0、3%、6%、10%、21%和100%时,DDTs降解率分别为80. 1%、76. 5%、78. 4%、81. 1%、88. 8%和94. 6%,ρ(O_3)分别为0、0. 20、0. 25、0. 40、0. 99和1. 93 mg/L.随着φ(O_2)的增加,ρ(O_3)逐渐增大,除氮气气氛外,DDTs降解率均逐渐增大,当φ(O_2)超过10%时,DDTs降解率较氮气气氛下更高. p,p'-DDD降解率均为100%,p,p'-DDE和o,p'-DDT的降解率随φ(O_2)的增加而增大.氮气气氛下p,p'-DDT降解率高于低浓度氧气气氛,除氮气气氛外,p,p'-DDT降解率随φ(O_2)的增加而增大.(2)当等离子体温度分别为80、100和150℃时,DDTs降解率分别为88. 8%、83. 2%和56. 3%,ρ(O_3)分别为0. 99、0. 65和0. 35 mg/L.当载气湿度为0、1. 0、2. 7和20. 5 g/m~3时,DDTs降解率分别为88. 8%、81. 6%、68. 6%和30. 0%,ρ(O_3)分别为0. 99、0. 73、0. 56和0. 32 mg/L.随着等离子体温度升高、载气湿度增大,反应器内ρ(O_3)逐渐减小,DDTs降解率也随之降低.(3)DDTs降解率随脉冲电压的升高而增大,当脉冲电压为24 k V、脉冲频率为50 Hz、等离子体温度为80℃、气体在反应器中的停留时间为10 s时,DDTs降解率达86. 9%.研究显示,脉冲电晕放电等离子体能够快速、有效地去除热脱附尾气中的DDTs.
In order to optimize the treatment of thermal desorption off-gas by non-thermal plasma,pulsed corona discharge plasma was applied to remove DDTs in thermal desorption off-gas. The effects of oxygen concentration,plasma temperature,humidity and pulse voltage on DDTs removal were investigated. The important role of ozone in DDTs degradation was also analyzed. The results indicated that:( 1) When the oxygen concentrations were 0,3%,6%,10%,21% and 100%,the DDTs degradation efficiencies were 80. 1%,76. 5%,78. 4%,81. 1%,88. 8% and 94. 6%,and the ozone concentrations were 0,0. 20,0. 25,0. 40,0. 99 and 1. 93 mg/L,respectively.Ozone concentration increased with increasing oxygen concentration. The degradation efficiency of DDTs increased with the increase of oxygen concentration in the gas stream. When the oxygen concentration exceeded 10%,the degradation efficiency of DDTs was higher under oxygen atmosphere than under nitrogen atmosphere. With the increase of oxygen concentration,the degradation efficiency of p,p'-DDE and o,p'-DDT increased,and p,p'-DDD was degraded completely. The degradation efficiency of p,p'-DDT under nitrogen atmosphere was higher than that at low oxygen concentrations. The degradation efficiency of p,p'-DDT increased with the increase of oxygen concentration.( 2) When the plasma temperatures were 80,100 and 150 ℃,the DDTs degradation efficiencies were 88. 8%,83. 2% and 56. 3%,the ozone concentrations were 0. 99,0. 65 and 0. 35 mg/L,respectively. When the humidity was 0,1. 0,2. 7 and20. 5 g/m~3,the DDTs degradation efficiencies were 88. 8%,81. 6%,68. 6% and 30. 0%,the ozone concentrations were 0. 99,0. 73,0. 56 and 0. 32 mg/L,respectively. The ozone was generated in the reactor and the DDTs degradation efficiency gradually decreased with the increase of the plasma temperature and the humidity of off-gas.( 3) The DDTs removal efficiency increased with the increase of the pulse voltage. It was 86. 9% when off-gas was treated by 80 ℃ plasma for 10 s at the pulse voltage of 24 k V and the pulse frequency of 50 Hz. In conclusion,the pulsed corona discharge plasma can effectively remove DDTs in thermal desorption off-gas.
In order to optimize the treatment of thermal desorption off-gas by non-thermal plasma,pulsed corona discharge plasma was applied to remove DDTs in thermal desorption off-gas. The effects of oxygen concentration,plasma temperature,humidity and pulse voltage on DDTs removal were investigated. The important role of ozone in DDTs degradation was also analyzed. The results indicated that:( 1) When the oxygen concentrations were 0,3%,6%,10%,21% and 100%,the DDTs degradation efficiencies were 80. 1%,76. 5%,78. 4%,81. 1%,88. 8% and 94. 6%,and the ozone concentrations were 0,0. 20,0. 25,0. 40,0. 99 and 1. 93 mg/L,respectively.Ozone concentration increased with increasing oxygen concentration. The degradation efficiency of DDTs increased with the increase of oxygen concentration in the gas stream. When the oxygen concentration exceeded 10%,the degradation efficiency of DDTs was higher under oxygen atmosphere than under nitrogen atmosphere. With the increase of oxygen concentration,the degradation efficiency of p,p'-DDE and o,p'-DDT increased,and p,p'-DDD was degraded completely. The degradation efficiency of p,p'-DDT under nitrogen atmosphere was higher than that at low oxygen concentrations. The degradation efficiency of p,p'-DDT increased with the increase of oxygen concentration.( 2) When the plasma temperatures were 80,100 and 150 ℃,the DDTs degradation efficiencies were 88. 8%,83. 2% and 56. 3%,the ozone concentrations were 0. 99,0. 65 and 0. 35 mg/L,respectively. When the humidity was 0,1. 0,2. 7 and20. 5 g/m~3,the DDTs degradation efficiencies were 88. 8%,81. 6%,68. 6% and 30. 0%,the ozone concentrations were 0. 99,0. 73,0. 56 and 0. 32 mg/L,respectively. The ozone was generated in the reactor and the DDTs degradation efficiency gradually decreased with the increase of the plasma temperature and the humidity of off-gas.( 3) The DDTs removal efficiency increased with the increase of the pulse voltage. It was 86. 9% when off-gas was treated by 80 ℃ plasma for 10 s at the pulse voltage of 24 k V and the pulse frequency of 50 Hz. In conclusion,the pulsed corona discharge plasma can effectively remove DDTs in thermal desorption off-gas.
引文
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[24] SUN Y X,HAKODA T,CHMIELEWSKI A G,et al.Mechanism of1,1-dichloroethylene decomposition in humid air under electron beam irradiation[J].Radiation Physics&Chemistry,2001,62(4):353-360.
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[26] VANRAES P,WILLEMS G,DAELS N,et al. Decomposition of atrazine traces in water by combination of non-thermal electrical discharge and adsorption on nanofiber membrane[J]. Water Research,2015,72(9):361-371.
[27] KARUPPIAH J,REDDY E L,REDDY P M,et al. Abatement of mixture of volatile organic compounds(VOCs)in a catalytic nonthermal plasma reactor[J]. Journal of Hazardous Materials,2012,237238(6):283-289.
[28] CHEN H,STANIER C O,YOUNG M A,et al. A kinetic study of ozone decomposition on illuminated oxide surfaces[J]. Journal of Physical Chemistry A,2011,115(43):11979-11987.
[29]李杰,赵先军,商克峰,等.沿面放电生成臭氧的传输损耗研究[J].高电压技术,2016,42(2):349-353.LI Jie,ZHAO Xianjun,SHANG Kefeng,et al.Study on transmission loss of ozone generated by surface discharge[J]. High Voltage Engineering,2016,42(2):349-353.
[30]章旭明.低温等离子体净化处理挥发性有机气体技术研究[D].杭州:浙江大学,2011.
[31] NIE Y,ZHENG Q,LIANG X,et al. Decomposition treatment of SO2F2using packed bed DBD plasma followed by chemical absorption[J]. Environmental Science&Technology,2013,47(14):7934-7939.
[32] WANG T C,LU N,LI J,et al.Degradation of pentachlorophenol in soil by pulsed corona discharge plasma[J]. Journal of Hazardous Materials,2010,180(123):436-441.
[2]汪光,吕永龙,史雅娟,等.北京东南化工区土壤有机氯农药污染特征和分布规律[J].环境科学与技术,2010,33(9):91-96.WANG Guang,LV Yonglong,SHI Yajuan,et al. Characterization and distribution of organochlorine pesticides in soils from Beijing southeast chemical industrial zone[J]. Environmental Science&Technology(China),2010,33(9):91-96.
[3] VOLDNER E C,LI Yifan. Global usage of selected persistent organochlorines[J]. Science of the Total Environment,1995,160:201-210.
[4] TURUSOV V,RAKITSKY V,TOMATIS L. Dichlorodiphenyltrichloroethane(DDT):ubiquity,persistence,and risks[J].Environmental Health Perspectives,2002,110(2):125-128.
[5] LI Jian,LI Na,MA Mei,et al. In vitro profiling of the endocrine disrupting potency of organochlorine pesticides[J]. Toxicology Letters,2008,183(1):65-71.
[6] GAO Yanfei,YANG Hong,ZHAN Xinhua,et al. Scavenging of BHCs and DDTs from soil by thermal desorption and solvent washing[J].Environmental Science and Pollution Research,2013,20(3):1482-1492.
[7] ARESTA M,DIBENEDETTO A,FRAGALE C,et al. Thermal desorption of polychlorobiphenyls from contaminated soils and their hydrodechlorination using Pd-and Rh-supported catalysts[J].Chemosphere,2007,70(6):1052-1058.
[8] PAL D,FANN S,WIGHT S. Application guide for thermal desorption systems[R]. California:Naval Facilities Engineering Service Center,1998:16-23.
[9] QI Zhifu,CHEN Tong,BAI Sihong,et al.Effect of temperature and particle size on the thermal desorption of PCBs from contaminated soil[J]. Environmental Science&Pollution Research,2014,21(6):4697-4704.
[10]许端平,何依琳,庄相宁,等.热解吸修复污染土壤过程中DDTs的去除动力学[J].环境科学研究,2013,26(2):202-207.XU Duanping,HE Yilin,ZHUANG Xiangning,et al. Desorption kinetics of DDTs from contaminated soil during processes of thermal desorption[J].Research of Environmental Sciences,2013,26(2):202-207.
[11] United States Environmental Protection Agency.Reference guide to non-combustion technologies for remediation of persistent organic pollutants in soil,second edition-2010[R].Cincinnati:Solid Waste and Emergency Response,2010:42-45.
[12] NUNEZ C M,RAMSEY G H,PONDER W H,et al. Corona destruction:an innovative control technology for VOCs and air toxics[J]. Journal of the Air&Waste Management Association,1993,43(2):242-247.
[13] ODA T,TAKAHAHSHI T,YAMAJI K. Nonthermal plasma processing for dilute VOCs decomposition[J]. IEEE Transactions on Industry Applications,2002,38(3):873-878.
[14]王奕文,张倩,伍斌,等.脉冲电晕放电等离子体去除污染土壤热脱附尾气中的DDTs[J].环境科学研究,2017,30(6):974-980.WANG Yiwen,ZHANG Qian,WU Bin,et al. Removal of DDTs in thermal desorption off-gas by pulsed corona discharge plasma[J].Research of Environmental Sciences,2017,30(6):974-980.
[15] SUARASAN I,GHIZDAVU L,GHIZDAVU I,et al. Experimental characterization of multi-point corona discharge devices for direct ozonization of liquids[J]. Journal of Electrostatics,2002,54(2):207-214.
[16] ABD A Z,WHITEHEAD J C,MARTIN P. Remediation of dichloromethane(CH2Cl2)using non-thermal,atmospheric pressure plasma generated in a packed-bed reactor[J].Environmental Science&Technology,2014,48(1):558-565.
[17]王铁成.场地有机物污染土壤的脉冲放电等离子体修复方法和机理研究[D].大连:大连理工大学,2013.
[18]高树香,陈宗柱.气体导电[M].南京:南京工学院出版社,1988:87-93.
[19]区瑞锟.介质阻挡放电等离子体中的活性粒子及其降解甲醛的研究[D].广州:华南理工大学,2011.
[20] WANG T C,LU N,LI J,et al. Degradation characteristics of pentachlorophenol in soil under different plasmas using pulsed electrical discharge[J]. International Journal of Plasma Environmental Science&Technology,2010,4(2):101-107.
[21] VISSCHER A D,DEWULF J,DURME J V,et al. Non-thermal plasma destruction of allyl alcohol in waste gas:kinetics and modelling[J].Plasma Sources Science&Technology,2008.doi:10.10880963-0252171015004.
[22] AERTS R,TU X,VAN G W,et al.Gas purification by nonthermal plasma:a case study of ethylene[J]. Environmental Science&Technology,2013,47(12):6478-6485.
[23] FALKENSTEIN Z.The influence of ultraviolet illumination on OH formation in dielectric barrier discharges of ArO2H2O:the Joshi effect[J].Journal of Applied Physics,1997,81(11):7158-7162.
[24] SUN Y X,HAKODA T,CHMIELEWSKI A G,et al.Mechanism of1,1-dichloroethylene decomposition in humid air under electron beam irradiation[J].Radiation Physics&Chemistry,2001,62(4):353-360.
[25] PEYROUS R,PIGNOLET P,HELD B. Kinetic simulation of gaseous species created by an electrical discharge in dry or humid oxygen[J].Journal of Physics D:Applied Physics,2000,22(11):1658-1667.
[26] VANRAES P,WILLEMS G,DAELS N,et al. Decomposition of atrazine traces in water by combination of non-thermal electrical discharge and adsorption on nanofiber membrane[J]. Water Research,2015,72(9):361-371.
[27] KARUPPIAH J,REDDY E L,REDDY P M,et al. Abatement of mixture of volatile organic compounds(VOCs)in a catalytic nonthermal plasma reactor[J]. Journal of Hazardous Materials,2012,237238(6):283-289.
[28] CHEN H,STANIER C O,YOUNG M A,et al. A kinetic study of ozone decomposition on illuminated oxide surfaces[J]. Journal of Physical Chemistry A,2011,115(43):11979-11987.
[29]李杰,赵先军,商克峰,等.沿面放电生成臭氧的传输损耗研究[J].高电压技术,2016,42(2):349-353.LI Jie,ZHAO Xianjun,SHANG Kefeng,et al.Study on transmission loss of ozone generated by surface discharge[J]. High Voltage Engineering,2016,42(2):349-353.
[30]章旭明.低温等离子体净化处理挥发性有机气体技术研究[D].杭州:浙江大学,2011.
[31] NIE Y,ZHENG Q,LIANG X,et al. Decomposition treatment of SO2F2using packed bed DBD plasma followed by chemical absorption[J]. Environmental Science&Technology,2013,47(14):7934-7939.
[32] WANG T C,LU N,LI J,et al.Degradation of pentachlorophenol in soil by pulsed corona discharge plasma[J]. Journal of Hazardous Materials,2010,180(123):436-441.