柠檬酸强化纳米零价铁活化过硫酸钠体系降解水溶液中的三氯乙烯

Enhanced trichloroethylene degradation in aqueous solution by citric acid and nanoscale zero-valent iron activated sodium persulfate system

采用螯合剂柠檬酸(CA)强化纳米零价铁(nZVI),活化过硫酸钠(PS)体系,降解水溶液中的三氯乙烯(TCE),分别考察了PS、CA、nZVI投加量、溶液初始pH和无机阴离子对TCE降解效果的影响,确定了在TCE降解过程中起主导作用的活性氧自由基,并验证了PS/nZVI/CA体系降解实际地下水中TCE的效果。结果表明:投加适量的CA可以明显提高PS/nZVI体系对TCE的降解效果,但当CA浓度过高时,TCE降解反而受到抑制,过量或不足的PS、nZVI均会降低TCE的降解率;当溶液初始pH为3~9时,PS/nZVI/CA体系可有效降解TCE;溶液中存在的Cl^-和HCO3^-会抑制TCE的降解,其中HCO3^-的抑制作用大于Cl^-;自由基清除实验和电子顺磁共振实验表明PS/nZVI/CA体系中产生了HO·、SO4^-·和O 2^-·活性氧自由基,其中HO·、SO4^-·对TCE降解起主导作用;CA的加入有利于实际地下水中TCE的降解,PS/nZVI/CA体系相比PS/nZVI体系,更适应实际地下水中各种水质条件的冲击,具有实际应用前景。

The chemical degradation performance of trichloroethylene(TCE)in aqueous solution by citric acidenhanced nanoscale zero-valent iron(nZVI)activated sodium persulfate(PS)system was investigated.The effects of various factors,including the dosages of PS,CA,nZVI,initial solution pH and common inorganic anions concentration(Cl^-,HCO3^-)on TCE degradation were evaluated.The generation of reactive oxygen species(ROS)was elucidated by free radical scavenger test and electron paramagnetic resonance(EPR)analysis.Moreover,TCE degradation performance by PS/nZVI/CA system in actual groundwater was tested The results indicated that the addition of CA in moderate dosages could remarkably enhance TCE removal,bu excessive dose of CA had an inhibitive effect on TCE degradation.Excessive or deficient dosages of PS and nZVI could cause the reduction in TCE degradation rate.TCE could be effectively degraded by PS/nZVI/CA system within a wider pH range of 3~9.Cl^- and HCO3^- in solution had inhibitive effects on TCE removal,of which the inhibitive effect of HCO3^- was higher.The scavenging tests and EPR detection confirmed that HO·SO4^-·and O2^-·were generated,and HO·and SO4^-·were the dominant radicals responsible for TCE degradation in PS/nZVI/CA system.PS/nZVI/CA system had better adaptation to the impact of actual groundwater constituents than PS/nZVI system,and TCE degradation efficiency by PS/nZVI system was improved by CA addition when implemented in actual groundwater,indicating that PS/nZVI/CA system has practical application prospects in the remediation of TCE contaminated groundwater.