过碳酸钠-过硫酸钠双氧化体系降解地下水中三氯乙烯

Degradation of Trichloroethylene from Groundwater by Sodium Percarbonate and Sodium Persulfate Double Oxidation System

为了解决单一氧化体系降解地下水中三氯乙烯的效率不高的问题,采用柠檬酸螯合Fe^(2+)催化过碳酸钠与过硫酸钠协同降解地下水中的三氯乙烯,考察过碳酸钠和过硫酸钠的配比、水质条件(pH、典型阴离子)以及三氯乙烯的初始浓度对三氯乙烯降解效率的影响。结果表明,当三氯乙烯的初始浓度为0.16 mmol/L时,在中性条件下,柠檬酸螯合Fe^(2+)催化过碳酸钠-过硫酸钠双氧化体系可以显著提高地下水中三氯乙烯的降解速率;三氯乙烯的降解受过碳酸钠与过硫酸钠的配比的影响,过碳酸钠、过硫酸钠、柠檬酸、 Fe^(2+)、三氯乙烯的物质的量比为10∶8∶5∶10∶1时,反应180 min后三氯乙烯的降解率为98.5%;随着反应体系pH增大,三氯乙烯的降解率逐渐降低;地下水中常见的阴离子SO_(4)^(2-)、 NO_(3)^(-)对该双氧化体系去除地下水中三氯乙烯的影响较小,但较高浓度的HCO_(3)^(-)、 Cl^(-)显著抑制三氯乙烯的降解;自由基清扫实验确定双氧化体系中存在氢氧自由基HO·、硫酸根自由基SO_(4)^(-)·、超氧自由基O_(2)^(-)·等自由基,且HO·对三氯乙烯的降解起主导作用。

To solve the problem of low efficiency in the degradation of trichloroethylene in groundwater by a single oxida-tion system,citric acid chelated Fe^(2+)was used to catalyze the synergistic degradation of trichlorethylene in groundwater by sodium percarbonate and sodium persulfate.The effects of the ratio of sodium percarbonate and sodium persulfate,water quality conditions(pH,typical anions)and the initial concentration of trichlorethylene on the degradation effect of tri-chlorethylene were investigated.The results show that when the initial concentration of trichlorethylene is 0.16 mmol/L,citric acid chelated Fe^(2+)catalyzing sodium percarbonate and sodium persulfate double oxidation system can significantly increase the degradation rate of trichlorethylene in groundwater under neutral conditions.The degradation of trichloroethy-lene is influenced by the ratio of sodium percarbonate to sodium persulfate.When the molar ratio of sodium percarbonate,sodium persulfate,citric acid,Fe^(2+),and trichloroethylene is 10∶8∶5∶10∶1,the degradation rate of trichlorethylene after 180 min of reaction is 98.5%.The pH has a certain influence on the degradation of trichlorethylene,and the degradation rate of trichlorethylene decreases gradually with the increasing of pH.The common anions SO2-4,and NO-3 in ground-water have a relatively small impact on the removal of trichloroethylene from groundwater by this double oxidation system,but higher concentrations of HCO_(3)^(-) and Cl^(-)significantly inhibit the degradation of trichloroethylene.The free radical scavenging experiments determine the presence of free radicals such as hydroxyl radical HO·,sulfate radical SO_(4)^(-)·,superoxide radical O_(2)^(-)·in the double oxidation system,and HO·plays a leading role in the degradation of trichlorethylene.