热脱附耦合过硫酸盐对土壤苯并[a]芘去除效果研究

Study of thermal desorption coupled persulfate on removal of benzo[a]pyrene in soil

为提高低温热脱附技术对土壤高沸点多环芳烃污染物的去除效果,在电加热炉和土壤加热箱中分别模拟热脱附耦合过硫酸盐(PS)热氧化降解苯并[a]芘(Bap)的效果研究。结果表明:序批式试验中,在60℃条件下热活化PS可有效降解土壤中Bap污染物,120 min内去除率为48.4%,远优于单独PS氧化或单独热脱附的效果;Bap降解效果随着温度提高(40~90℃)、PS浓度增大(0.05~0.5 mol/L)以及水土质量比升高(0.5/1~2/1)而提高。在应用试验中,氧化剂PS的循环注入一定程度上影响了土壤升温速率,但在较高PS浓度注入下加热箱中各取样点位Bap的残留均能达到修复要求(<0.55 mg/kg);PS的持续分解表明热脱附耦合PS修复技术具有持续性。

To improve the removal of polycyclic aromatic hydrocarbons(PAHs),one kind of high boiling point contaminants in soil,by medium-low temperature thermal desorption process,thermal desorption coupled persulfate(PS)technology was investigated for PAHs-contaminated soil remediation through thermal-oxidation processes.In this study,benzo[a]pyrene(Bap)was selected as the characteristic contaminant,and two thermal-oxidation experiments of Bap were conducted.First of all,an electric heating furnace was used in the sequential batch study,and the effects of temperature,PS concentration,and water/soil ratio on Bap removal were explored.Secondly,a soil heating box equipped with electric heating rods and a reagent circulating injection device was used in the application verification research to simulate in situ soil remediation.The results of the sequencing batch study indicated that at 60℃,thermally activated PS could degrade Bap efficiently.Under the experimental conditions,the removal of Bap within 120 min reached up to 48.4%,which is more effective than that of both the single PS oxidation process and single thermal desorption process under the same conditions.In addition,the removal of Bap increases with the increase of temperature(from 40℃to 90℃),PS concentration(from 0.05 mol/L to 0.5 mol/L),and water/soil ratio(from 0.5/1 to 2/1)by several single factor experiments.Meanwhile,the results of application verification research demonstrated that the cyclic injection of PS oxidant solution under a circulation flow rate of 120-480 mL/min could affect the heating rate of the soil,while with a high concentration of PS injection,Bap removal at each sampling point in the heating box could meet the target for remediation(<0.55 mg/kg).Moreover,PS decomposed continuously under heating conditions and the decomposition rate was not affected by the initial PS concentration,implying that thermal desorption coupled PS technology was sustainable for contaminated soil remediation.