State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, 163 Xianlin Avenue, Nanjing 210023, China; Department of Applied Chemistry, Yuncheng University, 1155 Fudan West Street, Yuncheng 044000, China; Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, USA.
Key Laboratory for Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang 453007, China.
Sci Total Environ. 2020 Aug 20;731:139184. doi: 10.1016/j.scitotenv.2020.139184. Epub 2020 May 4.
In practice, regeneration of adsorbent is always achieved by heating with hot steam, leaving some water in the adsorbent bed, which may negatively affect the VOCs adsorption. In this research, adsorption isotherms of 12 VOCs (ketones, alkanes, alcohols, halohydrocarbons, and aromatic hydrocarbons) on granular activated carbon (GAC) with different initial water contents (IWC) were conducted. Adsorption interactions between VOCs and GAC at different IWC were investigated using the combination of Linear Solvation Energy Relationship (LSER) and Dubinin-Radushkevich (DR) equation. The results showed that initial water vapor could reduce adsorption capacities and partition coefficient of 12 VOCs, especially at low VOCs concentration. According to LSER, electron acceptor ability (∑β) and dispersive force (logL) of VOCs played major roles during adsorption. For VOCs with approximate ∑β value in the same series, the negative influence of IWC was less obvious for VOCs with higher logL, while for VOCs with similar logL value in different series, the negative influence of IWC was more significant for VOCs with higher ∑β. Furthermore, characteristic curves of 12 VOCs onto dry GAC, i.e., the plots of adsorbed volume (q) vs adsorption potential density (ε/V), fell essentially onto a single curve with a high correlation coefficient, while on GAC with IWC, characteristic curves of 12 VOCs had obvious discrepancy. Considering the effect of IWC, the contribution percentage of dispersive force (W) to VOCs adsorption was introduced to modify adsorbed volume (q) in DR equation and W·q was used instead of q. Then, the integrative characteristic adsorption curves of 12 VOCs on GAC with initial water could be modified well and they showed better superposition with higher fitting coefficient of DR equation. The results are meaningful to estimate adsorption capacities for other VOCs adsorption onto GAC within the range of IWC in this study.
在实践中，吸附剂的再生通常通过用热蒸汽加热来实现，这会在吸附剂床中留下一些水，从而可能对 VOCs 的吸附产生负面影响。在这项研究中，研究了在不同初始含水量（IWC）下，12 种 VOCs（酮类、烷烃、醇类、卤代烃和芳烃）在颗粒活性炭（GAC）上的吸附等温线。通过将线性溶剂化能关系（LSER）和杜宾宁-拉什科夫斯基（DR）方程相结合，研究了不同 IWC 下 VOCs 与 GAC 之间的吸附相互作用。结果表明，初始水蒸气会降低 12 种 VOCs 的吸附容量和分配系数，特别是在低 VOCs 浓度下。根据 LSER，VOCs 的电子受体能力（∑β）和色散力（logL）在吸附过程中起主要作用。对于同一系列中∑β 值相近的 VOCs，IWC 的负面影响对于 logL 值较高的 VOCs 较小，而对于不同系列中 logL 值相近的 VOCs，IWC 的负面影响对于∑β 值较高的 VOCs 更为显著。此外，12 种 VOCs 在干燥 GAC 上的特征曲线，即吸附体积（q）与吸附势能密度（ε/V）的关系图，本质上都落在一条具有高相关系数的单一曲线上，而在具有 IWC 的 GAC 上，12 种 VOCs 的特征曲线则存在明显差异。考虑到 IWC 的影响，引入了色散力（W）对 VOCs 吸附的贡献百分比来修正 DR 方程中的吸附体积（q），并用 W·q 代替 q。然后，具有初始水的 12 种 VOCs 在 GAC 上的综合特征吸附曲线可以得到很好的修正，并且它们与 DR 方程的拟合系数更高，具有更好的叠加效果。研究结果对在本研究范围内 IWC 下估算其他 VOCs 在 GAC 上的吸附容量具有重要意义。
