Na2S2O8、H2O2在氧化处理石油污染土壤中的持续有效性研究

以过氧化氢(H_2O_2)和过硫酸钠(Na_2S_2O_8)为氧化剂,通过室内模拟实验,研究不同氧化剂及分次添加方式(1次或分3次)、外源添加零价铁(ZVI)处理对石油污染土壤中石油烃类污染物的去除能力,探讨了不同处理下氧化剂的持续性和去除污染物的有效性。结果表明:在氧化剂初始浓度为21、63、105 mmol·L~(-1)的处理中,H_2O_2在反应第2 d均已检测不到,Na_2S_2O_8剩余量在反应10 d后分别为11、35、60 mmol·L~(-1);反应10 d后,总石油烃类(TPH)总去除率在氧化剂初始浓度为63、105 mmol·L~(-1)的Na_2S_2O_8处理中显著高于H_2O_2处理(P0.05),分别高出12.41%、14.21%;在第4～10 d Na_2S_2O_8和TPH剩余浓度的降低均非常缓慢,表明土壤中能活化Na_2S_2O_8的物质不足;加入ZVI显著提高了TPH总去除率(P0.05),尤其促进了第4～10 d TPH的持续降解(分别增加了8.46%、8.49%、12.26%)。总量相等的H_2O_2分3次在第0、24、48 h投加,反应10 d后TPH降解率比一次性投加分别提高了17.26%、25.43%、28.11%。通过对反应体系有机组分的GC-MS图谱分析,反应10 d后H_2O_2分3次添加、ZVI活化Na_2S_2O_8处理中石油烃类总峰值分别降低了56.64%和57.60%,且部分长链烷烃被降解为相对较短的烷烃组分。研究表明:Na_2S_2O_8在石油污染土壤中持续性优于H_2O_2,但Na_2S_2O_8去除TPH的有效性随反应时间增加而降低;添加ZVI提高了Na_2S_2O_8去除TPH的有效性;分批次投加H_2O_2提高了石油污染土壤中的TPH降解率。

Persistence and effectiveness of oxidants during the treatment of petroleum-contaminated soil by chemical oxidation with Na2S2O8 and H2O2

Hydrogen peroxide(H₂O₂)and sodium persulfate(Na₂S₂O₈)were used to treat petroleum-contaminated soil in laboratory experiments. The influences of different oxidants, fractional addition methods(1 or 3 times), and external addition of zero-valent iron(ZVI)on the degradation of total petroleum hydrocarbon(TPH)were investigated. The persistence of oxidants and the effectiveness of removing pollutants under different treatments were discussed. The results showed that H₂O₂ was not detected on the second day of the reaction, but the remaining amount of Na₂S₂O₈ was 11, 35, and 60 mmol·L^-1, respectively, after 10 days of reaction in treatments with initial oxidant concentration at 21, 63, and 105 mmol·L^-1. After 10 days of reaction, the total removal rate of TPH in Na₂S₂O₈ treatment was 12.41% and 14.21% higher than that in H₂O₂ treatment with the initial oxidant concentration at 63 mmol·L^-1 and 105 mmol·L-(1 P<0.05), respectively. The decrease of Na₂S₂O₈ and TPH residual concentration was extremely slow on the 4th to 10th day, indicating that the substances capable of activating Na₂S₂O₈ were insufficient in the soil. Adding ZVI to Na₂S₂O₈ treatment significantly promoted the total removal rate of TPH(P<0.05), and the degradation of TPH during days 4~10 increased by 8.46%, 8.49%, and 12.26%, respectively, with initial oxidant concentration at 21, 63, and 105 mmol·L^-1. When H₂O₂ was added in three portions at 0, 24, and 48 h, with initial total oxidant concentration at 21, 63, and 105 mmol·L^-1, TPH degradation rate rose by 17.26%, 25.43%, and 28.11%, respectively, after 10 days of reaction. GC-MS analysis of the organic components showed that the total peak area of petroleum hydrocarbons decreased by 56.64% and 57.60%, respectively, in treatments with H₂O₂ added in three portions and ZVI-activated Na₂S₂O₈, and some long-chain alkanes were degraded to relatively "short-chain" alkane component. The overall results show that persistence of Na₂S₂O₈ in petroleum-contaminated soil is superior to that of H₂O₂, but the effectiveness of Na₂S₂O₈ in removing TPH decrease with the reaction time. The addition of ZVI improve the effectiveness of Na₂S₂O₈ in removing TPH. Fractional addition of H₂O₂(added three times)increase the degradation rate of TPH in petroleum-contaminated soils.