VOCs-水蒸气竞争吸附机理的微尺度模拟研究

Adsorption technology based on porous materials is considered to be one of the most promising methods for VOCs pollution control. By the influence of season and districts, adsorption process of VOCs is often accompanied by water vapor, which plays an adverse effect on the adsorption of materials. Therefore, it is essential to investigate the influence mechanism of water vapor, and explore the relationship between structure and properties of materials, which would effectively instruct practice. This study will observe the diffusion and adsorption behavior of VOCs-water vapor mixtures from a microscopic level based on molecular simulation, then elucidate the mechanism of competitive adsoprtion in mixtures, which aimed at improving theoretical system. The authors will focus on the adsorbates firstly, to elucidate the diffusion competition in mixtures by analyzing the diffusion limitation and substitution function between adsorbates. Then investigate the interaction between adsorbates and adsorbent by exploring the key factors that influence adsorption behavior, and reveal the significant mechanism of preferential selectivity of adsorbent towards adsorbates. Finally, a quantitative relationship between structure and properties of activated carbon materials will be built, and the most preferential structures that facilitate adsorption behaviors will be indicated, which would provide scientific basis for the design, prediction and optimization of adsorption system.

以多孔材料为核心的吸附技术是有效的VOCs污染控制手段之一。受季节和区域影响，VOCs的吸附过程常伴随着水蒸气的吸附，将对材料的吸附效果产生不利影响。因此，探讨水蒸气的影响机理，揭示材料结构与性能的关系，将有效地指导实践。本项目以完善扩散和吸附理论为目标，应用分子模拟技术，从微观的层面研究VOCs-水蒸气混合体系的扩散和吸附行为，阐释多组分的竞争吸附机理。从吸附质入手，聚焦吸附质间的扩散限制效应和位点置换作用，探索吸附质间的扩散竞争关系。再过渡到吸附质与吸附剂的相互作用，分析影响吸附行为的关键结构要素，揭示材料的结构因素对混合组分的吸附选择机制。在此基础上，建立活性炭材料宏观的定量构-效关系，提出有利于VOCs吸附作用的结构因素，将为吸附系统的设计、预测和优化提供有效的科学依据。

以多孔材料为核心的吸附技术是有效的VOCs污染控制手段之一。探讨VOCs-水蒸气多组分的吸附竞争机理，能有效地揭示材料结构与性能的关系。本项目以完善吸附理论为目标，应用分子模拟技术，从微观的层面探讨VOCs和水蒸气混合组分的竞争吸附行为。双组分吸附体系中，随着相对湿度的增加，苯主要通过苯-水分子间的氢键作用吸附在水分子周围。吸附质在活性炭层表面形成了双层吸附形态，第一层是水分子，其平均距离为2.99~3.19Å，第二层为苯，其平均距离为4.67~6.17Å。而甲醛和水分子以活性炭表面亲水性的含氧官能团作为活性中心，形成了独立的甲醛分子簇和水分子簇。水分子簇通过水分子间的氢键作用沿官能团向外纵向生长，而甲醛则沿活性炭层向孔径内扩散，分子簇沿横向生长。苯-甲醛-水蒸气三元混合吸附体系中，在活性炭层表面和憎水性的孔径内，三种吸附质形成了多层吸附，第一层主要为水分子，甲醛通过与水分子间的氢键作用吸附在其周围，形成第二层吸附。第三层主要为苯，苯通过与甲醛的相互作用力吸附在甲醛的周围。而在含氧官能团附近，甲醛和水分子占据主要的吸附位点。当相对湿度增加到70%，甲醛分子簇消失，甲醛主要通过与水分子间的氢键作用实现吸附作用。本研究将为吸附系统的设计、预测和优化提供有效的科学依据。