基于目标导向的活性炭表面改性及其对含水多组分挥发性有机物气相吸附机理研究

Activated carbon as adsorbent is widely used in collecting and processing volatile organic compounds (VOCs), however, it is difficult to improve the gas phase adsorption performance for humid VOCs with multi-components. This research is based on the target of separation adsorption polar and non-polar VOCs, and infrared spectrometer, scan electric mirror, and Boehm titration are used to analyze chacteractions of activated carbon (surface area, hole structure and distribution, contact angle, and surface functional groups). The relationship between properties of VOCs and adsorption efficiency is clarified and the inherent correlations among different VOCs, surface micro-structure and adsorption properties of activated carbon is investigated. Characteristics，theories and methods of gas phase adsorption of modified activated carbon to humid VOCs are studied at three levels (adsorption of modified activate carbons to VOCs, its mechanism and application).Through understanding effects of different surfacal properties of activated carbon on adsorption polar/non-polar VOCs and selective behaviors of activated carbon to VOCs adsorption，parameters on selective and competitive adsorption performance are discussed. The activated carbon is characterized by infrared spectroscopy, microscopic observation, specific surface and pore size analysis and Boehm titration to analysis its surface area, and surface functional groups, and pore distribution features. The experimental study of the adsorption of activated carbon to VOCs is conducted by the isothermal adsorption experimental apparatus. By experments of adsorption to VOCs at different relative humidity and with different VOCs, adsorption performance of the multistage adsorption system of modified activated carbon for humid VOCs and multicomponent VOCs are selected. A COSMO-RS mathematical models is used to conduct analysis of VOCs under different humidity adsorbent on the partition coefficient, water content change analysis of surface functional groups of activated carbon on adsorption mechanism of VOCs. Modified activated carbon is applied to soil remediation in a contaminated site to assess its adsorption effect on VOCs with complex composition. It will provide with the scientific basis for soil sample collection and soil VOCs removal.

活性炭作为吸附剂广泛应用于挥发性有机物(VOCs)的收集和处理，而如何提高活性炭对含水多组分VOCs的气相吸附是该领域亟待解决的难题。本研究基于分离吸附极性组分和非极性组分VOCs的目标，借助红外光谱仪、扫描电镜、Boehm滴定等手段，在分析活性炭物性（表面积、孔性、接触角、表面官能团组成和含量）与单组分VOC吸附性能的构效关系的基础上，通过吸附等温曲线、改性技术筛选和改性条件优化，分析改性活性炭吸附不同湿度多组分非极性/极性VOCs的分配系数和吸附效果与活性炭物性之间的关系，阐明提高其吸附多组分非极性/极性VOCs性能的改性方案，结合COSMO-RS模型揭示改性活性炭气相吸附含水多组分VOCs的机理，进而建立可实现VOCs广谱性吸附和多组分分离吸附的多级活性炭吸附体系，并评价该体系在土壤VOCs去除的实际应用的适用性。本研究将为土壤VOCs样品收集和土壤VOCs污染治理提供科学依据。

选择聚二甲基硅氧烷（PDMS）作为改性剂，采用加热冷凝法获得具有PDMS疏水涂层的改性活性炭，研究改性活性炭对含水VOCs吸附效果。采用BET比表面积分析、扫面电镜（SEM）、Boehm滴定、X射线能谱（XPS）等方法对PDMS改性前后活性炭进行表征；测定不同湿度下活性炭和改性活性炭水蒸汽吸附等温线；在相对湿度为0%、50%和90%时测定活性炭和改性活性炭对VOCs吸附穿透曲线;针对含水蒸气VOCs的吸附，通过一系列的活性炭改性研究，获得具有疏水性表面涂层活性炭，研究优化了活性炭疏水性形成的条件以提高活性炭对含水蒸汽VOCs的选择性吸附，研究对含水VOCs选择性吸附的改性活性炭及其制备和再生方法。经PDMS改性后，活性炭表面疏水性增大，同时BET比表面积和微孔容积减小。水蒸汽吸附等温线表明PDMS改性降低了活性炭对水蒸汽吸附能力，改性温度越高，水蒸汽吸附量降低越大，改性温度250℃时活性炭水蒸汽吸附量降低了59%。活性炭水蒸汽吸附能力与活性炭微孔容积、表面酸性官能团和表面水接触角有关。含水VOCs吸附穿透曲线表明与原始活性炭相比，PDMS改性活性炭在吸附甲苯、苯蒸气时，吸附过程受水蒸气影响较小，甲苯、苯吸附量增大；PDMS改性活性炭对丙酮吸附吸附选择能力提高不明显，这可能与VOCs分子极性大小有关。主要创新：（1）不同条件下改性活性炭对水蒸汽吸附的影响因素，分析影响活性炭吸附水蒸汽关键因素及其量化关系，为活性炭目标导向性改性提供了新思路。（2）采用加热冷凝法将PDMS涂层加载到活性炭表面，制成疏水性表面活性炭；研究不同相对湿度下PDMS涂层对活性炭吸附甲苯、苯、丙酮蒸汽的影响，对探索不同改性方法提高活性炭对含水VOCs吸附能力提供理论支持。采用动态吸附法研究了不同相对湿度条件下，PDMS改性活性炭对VOCs吸附的影响，探索其关键影响因素. (3)疏水性涂层活性炭的提高了活性炭对含水VOCs吸附，增加了对含水的多种VOCs的吸附能力，再生的活性炭对含水VOCs的吸附没有明显下降。为应用于含VOCs废气处理和VOCs污染土壤采样技术领域提供技术支撑。