【作者】 王亚玲；

【导师】 蔡喜运；

【作者基本信息】 大连理工大学 ， 环境工程， 2023， 博士

【摘要】 石油工业生产过程的“跑冒滴漏”及事故性排放导致普遍的土壤及地下水污染,石油污染物组分复杂,主要包括烷烃、多环芳烃（PAHs）和苯系物。基于过硫酸盐的化学氧化修复技术具有高氧化效率和低成本的特点,被广泛应用于石油污染土壤修复。过硫酸盐氧化修复土壤效果受限于土壤污染特征和污染物形态的差异性以及氧化反应的复杂性,导致过硫酸盐氧化修复污染土壤效果变异性大。环糊精具有超分子识别功能,能调控污染物的物理化学特性与氧化反应过程,然而,环糊精对过硫酸盐氧化修复石油污染土壤的强化机制尚不清楚,限制了环糊精强化过硫酸盐修复技术的开发。因此,本研究综合考虑土壤污染特征和氧化修复过程的复杂性,识别了过硫酸盐氧化修复石油烃污染土壤的关键影响因素,揭示了环糊精强化过硫酸盐氧化修复石油烃污染土壤的机制,开发了新型环糊精活化材料及其强化过硫酸盐氧化技术。主要研究内容及结论如下:（1）基于土壤污染特征和过硫酸盐氧化修复过程的复杂性,构建了包含土壤性质、污染特征和过硫酸盐氧化修复技术参数的氧化修复效果综合影响模型。研究发现,模型包含有机质、铁和锰等土壤性质,石油烃有效态含量和有效态占比等污染物特征,及过硫酸盐投加量等技术参数以交互项组成的五项因子（n=319,R²=0.87）,外部验证（n=82）结果表明模型具有良好的预测能力,1倍偏差之内的预测准确率为91%。其中,铁-锰因子对过硫酸盐氧化修复石油烃污染土壤效果的贡献度最高（51.3%）,其次为含有石油烃有效态含量及有效态占比的因子（19.6%）和过硫酸盐氧化修复技术参数因子（18.0%）。有机质-污染物总量因子对过硫酸盐氧化修复石油烃污染土壤效果呈负影响,贡献度达到11.1%。过硫酸盐氧化修复效果综合影响模型识别了铁锰含量和污染物有效性等因素对过硫酸盐氧化修复石油烃污染土壤效果的影响规律。（2）利用Feflow模拟和吸附、解吸、传质及降解序批式实验,探究了环糊精强化过硫酸盐氧化降解土壤PAHs的机制。研究发现,环糊精强化过硫酸盐氧化降解土壤PAHs的过程是环糊精用量和污染物解吸、传质等环境过程的函数。环糊精通过抑制土壤吸附PAHs、促进PAHs解吸和加速PAHs传质过程强化过硫酸盐氧化降解土壤PAHs。土壤中PAHs解吸过程对环糊精投加量变化的响应敏感度（29.0%–54.0%）高于PAHs传质过程（19.9%–24.4%）。环糊精投加量影响PAHs解吸和传质过程对过硫酸盐氧化降解土壤PAHs效果的贡献度。其中,0.1%环糊精投加量条件下,环糊精促进PAHs解吸过程对过硫酸盐氧化修复PAHs污染土壤效果的贡献度最高,达到59.8%–82.9%。1.0%环糊精投加量条件下,环糊精促进PAHs传质过程对过硫酸盐氧化修复PAHs污染土壤效果的贡献度最高,达到76.3%–89.5%。（3）开发了具有活化过硫酸盐和加速污染物传质双重效应的环糊精涂层Fe₃O₄@Fe⁰核壳材料,构建了环糊精强化过硫酸盐氧化修复技术。研究发现,Fe₃O₄@Fe⁰-CD的环糊精涂层将Fe（Ⅳ）活性物种产率提高367%,水中PAHs传质速率提高51%,进而促进PAHs与Fe（Ⅳ）碰撞,实现污染物的快速去除。Fe₃O₄@Fe⁰-CD/PS降解萘的k_obs为0.571min^-1,是Fe₃O₄@Fe⁰/PS体系(0.019 min^-1)的30倍,18次补加萘/PS的循环降解实验中,Fe₃O₄@Fe⁰-CD/PS实现13次完全去除水体萘,Fe₃O₄@Fe⁰/PS仅1次完全去除,表明Fe₃O₄@Fe⁰-CD/PS可长效活化过硫酸盐高效降解水体萘。同时,Fe₃O₄@Fe⁰-CD通过促进土壤中石油污染物的解吸提高污染物的过硫酸盐氧化去除效果。污染土壤修复效果显示,Fe₃O₄@Fe⁰-CD/PS对石油污染物的去除率是Fe₃O₄@Fe⁰/PS体系的1.2–3.0倍,是1.0%-CaO/PS体系的1.4–9.8倍。综上,本研究阐明了土壤铁锰含量、石油污染物有效性和氧化剂添加量等因素对过硫酸盐氧化修复石油污染土壤效果的影响规律,揭示了环糊精促进PAHs解吸和传质过程强化过硫酸盐氧化修复污染土壤的机制,有助于环糊精强化过硫酸盐高效氧化修复技术的开发。更多还原

【Abstract】 Contamination of soils and groundwater by petroleum is a serious problem worldwide,due to the massive production and releasing of crude oil and petroleum-based products.Petroleum hydrocarbons（TPHs）mainly include alkanes,polycyclic aromatic hydrocarbons（PAHs）and monoaromatic hydrocarbons.Persulfate（PS）oxidation technology is widely used for petroleum contaminated soil remediation,due to high oxidation performance and efficiency-cost relation.PS oxidation of compounds in soils highly depends on contaminated soil properties and distributions of contaminants.Performance of PS oxidation systems is commonly limited by both complexities of soil pollution and oxidation processes.These performances lead to high variability,high cost and low instability of PS oxidation for petroleum contaminated soils.Cyclodextrins（CDs）are well-known host compounds with an unique advantage of molecular recognition.CDs are demonstrated to mediate oxidation reactions of contaminants by increasing the accessibility and reactivity of contaminants.However,the mechanisms by which CDs mediate PS oxidation of petroleum contaminants in soils remain unclear,which limits the further promotion and application of CDs-mediated PS oxidation technology.Therefore,comprehensive relationships of oxidation performance with soil properties,contaminants and technical process were developed to recognize important factors related to specification distribution,environmental transfer and oxidation potential of contaminants in soils,respectively.The mediated mechanisms of CDs on oxidation potential of petroleum in soils by PS were studied and CDs-based materials were developed to construct the efficient oxidation system.The main results are as follows:（1）Based on the complexity of soil properties and specification distribution of contaminants,the influence of soil properties and specification distribution of TPHs on removal efficiency of TPHs in soils by PS oxidation was elucidated.Comprehensive relationship of oxidation performances with soils,contaminants and technical processes was developed to recognize important factors related to specification distribution,environmental transfer and oxidation potential of TPHs in soils.These soils/TPHs properties and oxidant dose constituted five interrelated terms that were developed a predictive model of PS oxidation（n=319,R²=0.87）.Among them,Fe/Mn minerals contributed positively to removal efficiency of TPHs in soils,accounted for about 51.3%of the variation of TPHs removal,followed by TPHs availability-available TPHs（19.6%）,application parameters of PS oxidation（p H and oxidant dose,18.0%）.Chemical oxidant demand（SOM-Fe-TPHs）contributed negatively to removal of TPHs in soils and accounted for about 11.1%of the variation of TPHs removal.The interrelation-based model of PS oxidation of TPHs displayed high predictive accuracy of 91%（n=82）for a factor of 1.0 above and below the ideal fit.This comprehensive model identified of influencing factors（e.g.,Fe-Mn content and TPHs patterns）on remediation of petroleum contaminated soils by PS oxidation.（2）Based on numerical simulations and sequence experiments,the CD-mediated mechanism of PS oxidation of PAHs in soils was elucidated.Mediation effects of CDs on PAHs removal by PS were modeled as a function of CDs dose and environmental process of PAHs.CDs mediate the removal of PAHs in soils by PS oxidation through inhibition of adsorption of PAHs,promotion of desorption and acceleration of mass transfer processes of PAHs.The response sensitivity of PAHs desorption process in soils to the change of CDs dose（29.0%–54.0%）was higher than that of PAHs mass transfer process（19.9%–24.4%）.The CDs dose influenced the contribution of environmental processes on removal performance of PAHs in soils by PS oxidation.The contribution of desorption of PAHs in soils reached at 59.8%–82.9%at 0.1%-CDs dose,which was the highest relative to other environmental processes on PAHs removal.While the contribution of mass transfer process of PAHs（76.3%–89.5%）was the highest on removal PAHs in soils by PS at 1.0%-CDs dose.（3）Cyclodextrin-coated Fe₃O₄@Fe⁰ nanoparticles（Fe₃O₄@Fe⁰-CD）were developed to both efficiently activate persulfates and rapidly access hydrophobic PAHs.The CD nano-layer both stabilizes the polycrystalline structure of Fe₃O₄@Fe⁰ nanoparticles in water and rapidly binds hydrophobic PAHs in water.The stable polycrystalline structure of Fe₃O₄@Fe⁰ is favorable for the generation of large amounts of highly reactive Fe（Ⅳ）.The CD nano-layer accelerates the intragranular diffusion of PAHs in nanoparticles and thus the access to Fe（Ⅳ）.The two advantages of Fe₃O₄@Fe⁰-CD are responsible for the high reactivity,stability and selectivity of Fe₃O₄@Fe⁰-CD/PS in water toward PAHs.Fe₃O₄@Fe⁰-CD/PS had about 30-fold rate constants of naphthalene（Nap）in water as much as Fe₃O₄@Fe⁰/PS.Fe₃O₄@Fe⁰-CD/PS completely removed Nap in water during 13 of total 18 supplementations of Nap and/or PS,whereas Fe₃O₄@Fe⁰/PS completely removed Nap only at the first supplementation of Nap.Moreover,the removal efficiency of petroleum in soils by Fe₃O₄@Fe⁰-CD/PS was significantly positive to the concentration of PAHs desorbed from soil.The removal efficiency of petroleum contaminants in soils treated by Fe₃O₄@Fe⁰-CD/PS was 1.2–3.0 times that treated by Fe₃O₄@Fe⁰/PS,and 1.4–9.8 times that treated by 1.0%-CaO/PS.In summary,comprehensive relationship of PS oxidation performances with Fe-Mn content,oxidation potential of TPHs and technical process was elucidated,the CDs-mediated mechanism of PS oxidation of PAHs in soils was reveled,which contributes to the development of CDs-enhanced PS efficient oxidation technology.更多还原