Development of Separation Process of Heavy Metals by Adsorption with Molecular Imprinted Thermosensitive Microgel Particles

在这项工作中，研究了一种新型凝胶吸附剂，它可以通过温度变化选择性地吸附和/或解吸特定的重金属离子。利用分子印迹技术将与重金属离子相互作用的螯合基团引入热敏型n -异丙基丙烯酰胺（NIPAM）凝胶中。以铜（Cu）为靶金属，以N-（4-乙烯基苄基）乙二胺（Vb-EDA）为螯合单体。在特定温度下Cu离子的吸附量最大，该温度下凝胶的溶胀程度与制备凝胶时相同，可以进行变温吸附/解吸。这意味着在制备中记忆的吸附位点在特定温度下被复制。证实了1个Cu离子与2个Vb-EDA分子配位，凝胶对Cu离子具有选择性。此外，Langmui…More r等温线公式可以很好地描述平衡吸附量。然而，尽管使用了约100 μm的凝胶颗粒，但达到平衡吸附量需要100多个小时。由于吸附峰温度高于聚（NIPAM）的转变温度约32℃，因此认为热敏凝胶颗粒是通过疏水相互作用聚集的。为了解决这一问题，用阴离子可聚合表面活性剂制备了含有Vb-EDA的热敏微凝胶颗粒。这种微凝胶颗粒在聚（NIPAM）的转变温度以上稳定分散。虽然对Cu离子的吸附量和选择性的温度依赖性与上述磨粒凝胶几乎相同，但其吸附速率却大大提高。吸附量在100分钟内达到平衡。虽然还需要进一步的研究，因为这种微凝胶颗粒在处理上有问题，但开发一种新型热敏凝胶吸附剂的可能性更小

In this work, a novel gel adsorbent, which adsorbs and/or desorbs specific heavy metal ions selectively by temperature swing, were examined. The chelating groups, which interact with heavy metal ions, were introduced into the thermosensitive N-isopropylacrylamide (NIPAM) gel using the molecular imprinting technique. Copper (Cu) was selected as a target metal, and N-(4-vinylbenzyl)ethylenediamine (Vb-EDA) was used as a chelating monomer. The maximum adsorption amount of Cu ions was obtained at a specific temperature, at which the swelling degree of gel was the same as that in the preparation of gel, and the adsorption/desorption by temperature swing was possible. It means that the adsorption sites memorized in the preparation were reproduced at a specific temperature. It was confirmed that one Cu ion coordinates with two molecules of Vb-EDA, and that the gel has the selectivity for Cu ion. Furthermore, it was found that the equilibrium adsorption amount was well described by the Langmui … More r isotherm formula. However, it took more than 100 hours to reach the equilibrium adsorption amount, though the ground gel particles of about 100 μm were used. It was considered due to the fact that the thermosensitive gel particles aggregate by the hydrophobic interaction because the peak temperature of adsorption was above the transition temperature of poly(NIPAM), about 32℃. To alleviate this problem the thermosensitive microgel particles involving Vb-EDA were prepared with an anionic polymerizable surfactant. Such microgel particles dispersed stably above the transition temperature of poly(NIPAM). Although the temperature dependence of the adsorption amount and the selectivity for Cu ion were almost the same as those of the ground gel particles mentioned above, the adsorption rate was improved extremely. The adsorption amount reached the equilibrium within 100 minutes. Although it needs further investigations because such microgel particles have a problem for handling, the -possibility for the development of a novel thermosensitive gel adsorbent could be shown Less