改进Fenton氧化体系修复石油污染土壤的机理研究

It has brought serious pollution to soil resource due to the crude oil leakage, oily wastewater and oily waste slurry in the process of petroleum drilling, mining, refining and storage. The chemical oxidation method is one of the effective practices remediating the petroleum-contaminated soils. The organic pollutants of oily wastewater can be removed effectively by using of the traditional Fenton reaction (Fe2+/H2O2),which result in hydroxyl radical of the strong oxidizing power under the acidic condition of pH 3, but there are some limitations, including excessive reaction rate, regular addition of Fe2+ and the requirement of the pH≤3, which affect seriously efficiency of remediation of petroleum contaminated soil. It is intended to on the basis of physical and chemical properties of petroleum contaminated soil and pollution status in Jianghan oil field, using of pretreatment method such as ultrasonic vibration, chemical cleaning agents, the dynamic process of petroleum contaminants desorbed from soil colloids will be discussed by adopting the dual-equilibrium desorption (DED) model in this project. Application of orthogonal design and split-plot design, effect of the different types and different concentrations of oxidants, catalysts and different ultrasonic energy densities and other factors on the removal of petroleum contaminants in soil will be explored. It will be established that improved Fenton oxidation system with effective response can be occurred in neutral and alkaline pH conditions. The parameters of the oxidation will be optimized to suit for subsequent microbial processing. After inoculating high efficient petroleum degrading microorganisms which separated and screened from Jianghan oil fields and application with different nutritional additives, the indicators of total petroleum hydrocarbon contents and different hydrocarbon component contents in the soils will be determinated periodically. The degradational dynamic processes of petroleum contaminants in the soils will be simulated by using of mathematical models such as second-order dynamic equation and Richards equation. The goodness of fitting about the simulating equations will be tested and the geometric meaning of corresponding parameters will be stated. The intermediate product in the degradation process and the change of soil structure will be detected respectively by means of GC-MS and X-ray diffraction instruments. Application of appropriate capture agent, hydroxyl radical and superoxide ion radical generated from the oxidation process of the ultrasonic-Fenton oxidation system will be determined quantitatively by using of high performance liquid chromatography (HPLC) and fluorescence photometric analysis. The intrinsic reaction mechanism of the system will be explored. These research contents will provid the scientific basis for the remediation of petroleum contaminated soil.

传统的Fenton反应(Fe2+/H2O2)在pH为3的酸性条件下，产生具有强氧化力的羟基自由基，能有效地去除含油废水中的有机污染物，但在处理石油污染土壤时因反应速度过快、需定期补充Fe2+、控制pH值≤3等条件限制而影响其修复效果。本项目根据江汉油田石油污染土壤的理化性质及其污染程度，采用超声波振动、化学清洗剂等预处理方法，应用"双元平衡解吸(DED)模型"探讨从土壤胶体表面解吸石油烃类污染物的动力学过程；采用正交设计和裂区设计，探讨不同种类和浓度的氧化剂、催化剂及不同超声能量密度等处理对土壤中石油烃类污染物的去除效果，构建改进的Fenton氧化体系；以改进的Fenton氧化、超声-Fenton氧化等方法去除被解吸的石油污染物，并优化适宜于后续微生物修复的Fenton氧化条件，采用GC-MS、X射线衍射仪等多种手段检测降解中间产物及其土壤结构的变化，为石油污染土壤修复提供科学依据。

为了构建自然土壤pH条件下具有较强氧化能力和温和的改进型Fenton反应用于石油污染土壤修复，采用表面活性剂、超声波振动等预处理方法和改进Fenton联合处理试验，探讨了4种表面活性剂对中度石油污染土壤在不同时间下的解吸特征，并用对数回归方程显著地模拟了从土壤颗粒表面解吸污染物的动力学过程，分析了3种不同类型土壤上表面活性剂SDS和Fenton联合处理的效果，从不同功率、不同时间的超声处理对石油污染物及其组分的去除率揭示了最佳的超声处理参数，探讨了Fenton、改进型Fenton、超声+Fenton联用法等去除土壤中石油污染物的效果及其上述几个氧化体系中羟自由基产生量，结果表明：超声+Fenton处理比Fenton处理、络合剂改进的Fenton处理比无络合剂的Fenton处理、Fe2+比Fe3+催化的Fenton反应均显著提高了羟自由基产生量和土壤中C28-以下的正构烷烃、类异戊二烯烃、多环芳香烃和多环萜类饱和烃等石油污染物的去除率。根据江汉油田石油污染土壤的理化性质及其污染程度，以室内模拟石油污染土壤为对象，采用L8(4×24)正交试验设计，研究了4种络合剂类型、用量和[H2O2]/[Fe3+]比等因素对改进Fenton反应去除石油污染物效果及其正构烷烃组分的影响，结果表明4种络合剂改进的Fenton处理均比无络合剂的Fenton处理土壤中石油烃类去除率高，较高络合剂用量和氧化剂用量的Fenton处理，更有利于C21-正烷烃的分解，对姥鲛烷、植烷及iC16- iC17异构烷烃也有较好的降解效果。针对Fenton中的氧化剂改进进行了试验，比较了4种氧化剂类型对污染物去除率的动力学变化趋势，探讨了不同氧化剂浓度、氧化剂与催化剂的不同比例对土壤中石油污染物去除效果的影响，结果表明在氧化剂浓度相同时，H2O2对土壤中残油的去除率比Na2S2O8高，两者分别比对照增加了145.5%-238.7%和112.6%-167.5%，在催化剂用量相同时，达到最高残油去除率的浓度比分别为50:1和100:1。经改进Fenton氧化处理后的污染土壤接种筛选的优势石油降解菌，随着培养时间的延长，石油污染物氧化后各处理正构烷烃和多环芳烃浓度均比CK呈现出显著地下降趋势，表明经改进Fenton氧化后提高了三芳甾烷、硫芴、菲等石油污染物的可生物降解特性。以上结论可为石油污染土壤修复提供理论依据。