School of Civil and Environmental Engineering , Cornell University , Ithaca , New York 14853 , United States.
Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , United States.
ACS Appl Mater Interfaces. 2019 Feb 27;11(8):8089-8096. doi: 10.1021/acsami.8b22100. Epub 2019 Feb 15.
Organic contaminants at low concentrations, known as micropollutants, are a growing threat to water resources. Implementing novel adsorbents capable of removing micropollutants during packed-bed adsorption is desirable for rapid water purification and other efficient separations. We previously developed porous polymers based on cyclodextrins that demonstrated rapid uptake and high affinity for dozens of micropollutants (MPs) in batch experiments. However, these polymers are typically produced as powders with irregular particle size distributions in the range of tens of micrometers. In this powdered form, cyclodextrin polymers cannot be implemented in packed-bed adsorption processes because the variable particle sizes yield insufficient porosity packing and consequently generate high back-pressure. Here we demonstrate a facile approach to remove micropollutants from water in a continuous manner by polymerizing cyclodextrin polymer networks onto cellulose microcrystals to provide a core/shell structure. Batch adsorption experiments demonstrate rapid pollutant uptake and high accessibility of the cyclodextrins on the adsorbent. Similarly, column experiments demonstrate rapid uptake of a model pollutant with minimal back-pressure, demonstrating potential for use in packed-bed adsorption processes. Furthermore, the pollutant-saturated columns were regenerated using methanol and reused three times with almost no change in performance. Column experiments conducted with a mixture of 15 micropollutants at environmentally relevant concentrations demonstrated that removal was determined by the affinity of each micropollutant for cyclodextrin polymers. The cyclodextrin polymer grafted onto cellulose microcrystals is more resistant to both anaerobic and aerobic biodegradation as compared to cyclodextrins and unmodified cellulose crystals, presumably due to the aromatic cross-linkers, demonstrating persistence. Collectively, the findings from this study demonstrate a general strategy to incorporate novel cyclodextrin adsorbents onto cellulose substrates to enable rapid and efficient removal of micropollutants during packed-bed adsorption as well as their promising long-term stability and regeneration capabilities.
低浓度的有机污染物，即所谓的微污染物，对水资源构成了日益严重的威胁。在填充床吸附过程中使用能够去除微污染物的新型吸附剂对于快速水净化和其他高效分离是可取的。我们之前开发了基于环糊精的多孔聚合物，这些聚合物在批量实验中表现出对数十种微污染物（MPs）的快速吸收和高亲和力。然而，这些聚合物通常作为粉末生产，其粒径分布在几十微米范围内不规则。在这种粉末形式下，环糊精聚合物不能用于填充床吸附过程，因为不同的粒径导致孔隙率填充不足，从而产生高背压。在这里，我们展示了一种通过将环糊精聚合物网络聚合到纤维素微晶上来提供核/壳结构，以连续方式从水中去除微污染物的简便方法。批量吸附实验表明，污染物的吸收速度快，吸附剂中环糊精的可及性高。同样，柱实验表明，模型污染物的吸收速度快，背压最小，表明在填充床吸附过程中具有潜在用途。此外，使用甲醇对饱和污染物的柱子进行了再生，并重复使用了三次，性能几乎没有变化。在环境相关浓度下进行的 15 种微污染物混合物的柱实验表明，去除取决于每种微污染物与环糊精聚合物的亲和力。与环糊精和未改性的纤维素晶体相比，接枝到纤维素微晶上的环糊精聚合物更能抵抗厌氧和需氧生物降解，这可能是由于芳族交联剂的存在，表现出持久性。总的来说，这项研究的结果表明了一种将新型环糊精吸附剂整合到纤维素基质上的通用策略，以在填充床吸附过程中实现快速高效地去除微污染物，以及它们具有前景的长期稳定性和再生能力。
