Sorption of the organic cation metoprolol on silica gel from its aqueous solution considering the competition of inorganic cations.
Sorption of the organic cation metoprolol on silica gel from its aqueous solution considering the competition of inorganic cations.
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DOI：
10.1016/j.watres.2014.01.042
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发表时间：
2014-05
期刊：
影响因子：
12.8
通讯作者：
Susann Kutzner;M. Schaffer;H. Börnick;T. Licha;E. Worch
中科院分区：
文献类型：
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作者：
Susann Kutzner;M. Schaffer;H. Börnick;T. Licha;E. Worch
以有机一价阳离子美托洛尔为吸附剂，硅胶为吸附剂，进行了系统的批实验，考察了有机阳离子在荷电表面的吸附特性。测定了美托洛尔（在pH值约为6时质子化率> 99%）与一价和二价无机阳离子（Na+、NH 4+、Ca 2+和Mg 2+）竞争的吸附等温线，以评估它们对阳离子交换过程的影响，并确定进一步吸附相互作用的作用。吸附等温线可用指数函数（Freundlich等温线模型）描述，其指数一致（约为0.8）。在一般情况下，减少美托洛尔的吸附与无机阳离子浓度的增加。竞争离子的同价表现出类似的效果。在234.42 ~ 426.58（L/kg）0.77之间，即使在很高浓度的竞争性无机阳离子下，美托洛尔仍具有显著的吸附亲和力，其Freundlich系数KF0.77与离子类型有关。另外的柱实验证实了这种行为，这表明除了阳离子交换之外还存在进一步的相关相互作用。在随后的分批实验中，还研究了具有多于一种竞争离子的混合物的影响以及在低于零电荷点的pH（pH PZC <2.5）下减少的负表面电荷的影响。最后，研究表明，阳离子交换是最相关的，但不是唯一的机制，美托洛尔在硅胶上的吸附。
Systematic batch experiments with the organic monovalent cation metoprolol as sorbate and the synthetic material silica gel as sorbent were conducted with the aim of characterizing the sorption of organic cations onto charged surfaces. Sorption isotherms for metoprolol (> 99% protonated in the tested pH of around 6) in competition with mono-and divalent inorganic cations (Na+, NH 4+, Ca 2+, and Mg 2+) were determined in order to assess their influence on cation exchange processes and to identify the role of further sorptive interactions. The obtained sorption isotherms could be described well by an exponential function (Freundlich isotherm model) with consistent exponents (about 0.8). In general, a decreasing sorption of metoprolol with increasing concentrations in inorganic cations was observed. Competing ions of the same valence showed similar effects. A significant sorption affinity of metoprolol with ion type dependent Freundlich coefficients K F, 0.77 between 234.42 and 426.58 (L/kg) 0.77 could still be observed even at very high concentrations of competing inorganic cations. Additional column experiments confirm this behavior, which suggests the existence of further relevant interactions beside cation exchange. In subsequent batch experiments, the influence of mixtures with more than one competing ion and the effect of a reduced negative surface charge at a pH below the point of zero charge (pH PZC≈ 2.5) were also investigated. Finally, the study demonstrates that cation exchange is the most relevant but not the sole mechanism for the sorption of metoprolol on silica gel.