Sorption is an important natural and technical process. Sorption coefficients are typically determined in batch experiments, but this may be challenging for weakly sorbing compounds. An alternative method enabling analysis of those compounds is column chromatography. A column packed with the sorbent is used and sorption data are determined by relating sorbate retention to that of a nonretarded tracer. In this study, column chromatography was applied for the first time to study sorption of previously hardly investigated heterocyclic organic compounds to multiwalled carbon nanotubes (MWCNTs). Sorption data for these compounds are very limited in literature, and weak sorption is expected from predictions. Deuterium oxide was used as nonretarded tracer. Sorption isotherms were well described by the Freundlich model and data showed reasonable agreement with predicted values. Sorption was exothermic and physisorption was observed. H-bonding may contribute to overall sorption, which is supported by reduced sorption with increasing ionic strength due to blocking of functional groups. Lowering pH reduced sorption of ionizable compounds, due to electrostatic repulsion at pH 3 where sorbent as well as sorbates were positively charged. Overall, column chromatography was successfully used to study sorption of heterocyclic compounds to MWCNTs and could be applied for other carbon-based sorbents.

中文翻译：

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杂环有机化合物对多壁碳纳米管的吸附

吸附是重要的自然和技术过程。吸附系数通常在分批实验中确定，但这对于弱吸附性化合物可能具有挑战性。能够分析这些化合物的另一种方法是柱色谱法。使用填充有吸附剂的色谱柱，并通过将吸附物保留与未延迟示踪剂的保留相关来确定吸附数据。在这项研究中，首次使用柱色谱法研究了以前很少研究的杂环有机化合物对多壁碳纳米管（MWCNT）的吸附。这些化合物的吸附数据在文献中非常有限，并且从预测中预计吸附较弱。氧化氘用作非延迟示踪剂。Freundlich模型很好地描述了吸附等温线，数据显示与预测值合理吻合。吸附是放热的，并观察到了物理吸附。H键可能有助于整体吸附，这是由于官能团的封闭，吸附减少，离子强度增加所致。降低pH值会降低可电离化合物的吸附，这是因为pH值为3时静电排斥，使吸附剂和被吸附物带正电。总体而言，柱色谱法已成功用于研究杂环化合物对MWCNT的吸附，并可用于其他基于碳的吸附剂。由于功能基团的封闭，其吸附力降低，离子强度增加，从而得到支持。降低pH值会降低可电离化合物的吸附，这是因为pH值为3时静电排斥，使吸附剂和被吸附物带正电。总体而言，柱色谱法已成功用于研究杂环化合物对MWCNT的吸附，并可用于其他基于碳的吸附剂。由于官能团的封闭，其吸附作用降低，离子强度增加，从而得到支持。降低pH值会降低可电离化合物的吸附，这是因为pH值为3时静电排斥，使吸附剂和被吸附物带正电。总体而言，柱色谱法已成功用于研究杂环化合物对MWCNT的吸附，并可用于其他基于碳的吸附剂。