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到温敏性N-异丙基丙烯酰胺(NIPAM)凝胶中。以铜为目标金属，N-(4-乙烯基苄基)乙二胺(VB-EDA)为络合单体。在特定的温度下，凝胶对铜离子的最大吸附量达到最大，此时凝胶的溶胀度与凝胶的制备过程中的溶胀度相同，可以通过变温吸附/解吸。这意味着在制备过程中记忆的吸附位置是在特定温度下重现的。证实了一个铜离子与两个VB-EDA分子配位，并且该凝胶对铜离子具有选择性。此外，还发现平衡吸附量可用朗缪尔…很好地描述更多的R等温线公式。然而，即使使用约100μm的研磨凝胶颗粒，也需要100h以上的时间才能达到平衡吸附量。认为这是由于热敏性凝胶粒子通过疏水相互作用聚集，因为吸附峰值温度高于聚(NIPAM)的转变温度，约为32℃。为了缓解这一问题，用阴离子可聚合表面活性剂制备了含有VB-EDA的温敏性微凝胶颗粒。这种微凝胶粒子在聚(NIPAM)的转变温度以上稳定分散。虽然对铜离子的吸附量和选择性随温度的变化规律与上述凝胶颗粒基本相同，但吸附速率有了极大提高。吸附量在100分钟内达到平衡。虽然由于这种微凝胶颗粒存在操作上的问题而需要进一步的研究，但开发一种新型的热敏性凝胶吸附剂的可能性可能较小

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