【作者】 王克亮；

【导师】 叶代启；

【作者基本信息】 华南理工大学 ， 环境工程， 2012， 博士

【摘要】 多环芳烃是环境中广泛存在的一类持久性有机污染物，随着排放量的日益增加，其对环境及人类健康均构成严重威胁。因此，开展多环芳烃及其衍生物的吸附去除研究是当前非常重要的一项课题。鉴于此，本文选取萘作为多环芳烃的典型代表物，运用多种实验技术及分子模拟技术，详细研究了吸附剂有序介孔碳的制备及其对萘的吸附性能。综合考虑各种有序介孔碳制备方法的优缺点，本文以三嵌段聚合物F127为模板剂，酚醛树脂为碳源，在乙醇溶液中采用软模板法制备有序介孔碳。首先确定了酚醛树脂热聚温度为80℃，苯酚/甲醛摩尔比为1:3，前驱物焙烧条件为在N2保护下，以1℃/min升温至600℃，保持2h,再以5℃/min升温至900℃，保持2h。此外，分别采用硼酸和正癸烷做扩孔剂对有序介孔碳孔径进行调节，其孔径调控范围分别为3.4—4.7nm和3.4—4.2nm。而且，通过XRD、TEM、XPS、Raman、N2吸脱附及FT-IR等现代测试技术对有序介孔碳进行了表征，结果表明两种扩孔剂的添加并未改变其有序结构。目前，虽然科研人员提出了多种聚合物在溶液中自组装机理，但目前仍存在争议。为了更好的理解有序介孔碳的制备机理，也鉴于分子模拟技术中耗散粒子动力学方法对聚合物体系的有效应用，本文创新性的利用该模拟方法开展了对F127/酚醛树脂/乙醇体系自组装过程的研究。首先，根据各珠子体积近似相等的原则对体系内各物质粗粒化处理为P、E、T和R珠子，并确定了相互作用参数。其次，总体上研究了亲水端和疏水端组成不同的PEO-PPO-PEO型三嵌段聚合物在乙醇溶液中的自组装规律。然后，考察了温度和剪切速率对自组装结构的影响规律。最后，结合实验分别研究了F127/乙醇体系和F127/酚醛树脂/乙醇体系的自组装规律。结果得出选择适中的温度（k_BT=1），较低的剪切速率（0.01≤γ≤0.2）对有序介孔碳前驱物的制备有利。随着F127浓度从15%逐渐增大到75%，其在乙醇溶液中自组装的胶束结构经历了从球状，柱状，层状逐渐过渡到更复杂的立体结构的过程，且酚醛树脂的加入并未破坏F127在乙醇溶液中的胶束结构，而是以其为结构模板，很好的包裹在外面，这与制备实验中得出的结论相一致,从而得出有序介孔碳制备过程中F127的致孔机制及有序介孔碳的形成机理，为有序介孔碳制备提供了微观尺度上的理解和认识。本研究以实验制备的一系列不同孔径的有序介孔碳为吸附剂，通过对萘的吸附穿透曲线、吸附等温线、吸附热力学和吸附动力学等方面，分别研究了有序介孔碳对萘的吸附性能。实验结果表明有序介孔碳对萘具有优异的吸附性能，其对萘吸附容量与比表面积和表面基团间没有明显关系，而介孔孔径尺寸与孔径分布是影响其对萘吸附容量的关键因素，孔径介于2~3.5nm之间的孔径更有利于萘吸附过程。此外，萘在有序介孔碳上的吸附等温线与Langmuir吸附等温方程相吻合，其吸附动力学行为可用Langmuir吸附动力学方程很好地描述，热力学研究表明萘在有序介孔碳上的吸附为放热过程，属于物理吸附。萘在有序介孔碳上的吸附性能实验能够得到一些有价值的结论，但却无法直接给出吸附质萘在有序介孔碳上的吸附位，吸附状态等详细情况。由于受实验条件、表征技术限制和人为因素干扰，使得人们对有序介孔碳的一些重要微观结构特性还不是了解的十分透彻，进而严重影响到对此类材料结构上的优化、分子级设计、构-效关系研究及实用化进程，而分子模拟技术则是一种较为有效的补充手段。目前，有关介孔碳建模的文献大都采用的是粗粒化模型，但是随着现代计算机技术的飞速发展，粗粒化模型已经不太适合，细化的全原子结构模型表述介孔碳是未来趋势。因此，本文借鉴挖孔建模的方法在微孔、介孔分子筛设计中的成功经验，采用巨正则系综蒙特卡罗方法，依据实验合成的有序介孔碳的结构数据，利用分子建模技术创新性的建立了有序介孔碳的全原子结构模型，并通过模拟小角XRD、广角XRD以及对孔结构的模拟分析，对该结构模型进行了一系列的表征，结果表明该模型与实际样品具有相似的微观孔结构和宏观的二维六方有序结构，模型建立较为合理。在此基础上，详细地模拟研究了萘在该模型上的吸附行为及规律，结果表明吸附等温线显示出第IV类吸附等温线的特点，属于典型的介孔材料吸附；对萘的吸附量达105.4mg/g；吸附开始时其在介孔孔道中主要以单分子层吸附在孔壁为主，随着萘吸附量的逐渐增加，逐渐过渡到多层吸附，直至最后充满整个介孔孔道；经计算得到萘在有序介孔碳模型上的平均吸附热为16.8Kcal/mol，低于20Kcal/mol，因此该过程属于物理吸附；在其它吸附条件相同的情况下，随着孔径的增加萘吸附速率逐渐增大。以上结论均与实验结论相一致，揭示了有序介孔碳在气体吸附方面的构-效关系。更多还原

【Abstract】 Polycyclic aromatic hydrocarbons （PAHs）, known as one of the persistent organicpollutants, which have threatened people health and atmospheric environment seriously. Soit’s very important to investigate how to remove PAHs effectively. In this work,naphthalene is taken as target pollutant of PAHs, and we investigated systematically thepreparation of ordered mesoporous carbons （OMCs） and the naphthalene adsorptionperformance by experiment and molecular simulation. The relatively detailed summaries wereas followed:OMCs with tunable pore sizes were synthesized by soft-template method, using F127astemplate, resol as carbon source, and boric acid and decane as pore-regulator agent. First ofall, the thermal polymerization temperature of resol and the molar ratio of phenol andformaldehyde are determined at80℃and1:3. The calcination was carried out in a tubularfurnace at450℃for2h and at900℃for3h under N2flow, the heating rate was1℃min^-1below450℃and5℃min-1above450℃. Then, the prepared samples were characterized byXRD, TEM, FT-IR and N2adsorption-desorption, the results showed that the OMCs have wellordered2D-hexagonal structures and the pore sizes are finely tunable from3.4to4.7nm byusing boric acid and from3.4nm to4.2nm by using decane as the pore-regulator agent.Actually, the synthesis mechanism of OMCs by soft template method is still in disputednow. In this thesis，computer simulation is applied to simulate the preparation process ofOMCs by dissipative particle dynamics （DPD） method in order to better understanding thepreparation mechanism from a macroscopic perspective. Firstly, all substances in the systemwere described successfully by Course-Grain model and the DPD interaction parameters weredefined by calculation. Secondly, we studied the self-assembly behavior of PEO_n-PPO_m-PEO_ntype triblock copolymer in solution. Thirdly, the effect of temperature and shearing rate onmicellar structures of F127were studied too. Fourthly, with the increasing of F127concentration, the micellar structure in F127/Ethanol system changed from sphere, cylinder,layer to cubic structure, respectively. Also, the introduction of resol did not change themicellar structure of F127in ethanol solution. The simulation results showed that thecylindrical micelle of F127was formed with hydrophobic core and hydrophilic corona aroundthe micelle interior, and resol surrounded the hydrophilic corona, which means F127acted asa structure-directing agent and played a key role in the precursor formation of OMCs, whichcorresponded with the experimental results. The naphthalene adsorption experiments on OMCs indicated that the OMCs have strongadsorption affinity to naphthalene and the maximum adsorption capacity was shown to reachup to303.2mg g-1. Furthermore, the mesopore volume between2³.5nm of OMCs wascrucial to the adsorption capacity and OMCs with pore sizes of2³.5nm were much morefavorable for the naphthalene adsorption process. The adsorption isotherms of naphthalene onOMCs match well with the Langmuir adsorption isotherm. Theoretical studies show that theadsorption kinetics of naphthalene on OMCs can be well accounted for using the Langmuiradsorption kinetics equation.We could draw some valuable conclusions by naphthalene adsorption experiments, butthe experiments could not tell us directly what the adsorption location and adsorption state areexactly on the surface of OMCs. Actually, we still don’t know the microscopic structure ofOMCs very well because of the restriction of characterization technology, human factor andexperimental conditions. However, molecular simulation technology could make up thedisadvantages. In the work, grand canonical Monte Carlo （GCMC） method is applied tosimulate the naphthalene adsorption behavior on OMCs model. Firstly, the atomic structuremodel of OMCs was built by using molecular modeling technique, and then was characterizedby calculating the accessible solvent surface area, total pore volume, small-angle andwide-angle X-ray diffraction patterns. The observed steep adsorption increase in OMCs are oftype Langmuir IV with a clear H1-type hysteresis loop, this is characteristic of highly orderedmesoporous materials. And the naphthalene adsorption amount is105.4mg/g. Additionally,the adsorption heat is16.8Kcal/mol, which is less than20Kcal/mol and it means the process isphysical adsorption. Also, the adsorption rate rose with the increasing of pore size. Thesimulation results are proved and compared with corresponding experiment results.更多还原