Marshall Wayne E, Wartelle Lynda H
USDA-ARS-Southern Regional Research Center, 1100 Robert E. Lee Blvd., P.O. Box 19687, New Orleans, LA 70179-0687, USA.
Water Res. 2006 Jul;40(13):2541-8. doi: 10.1016/j.watres.2006.04.030. Epub 2006 Jun 9.
Ion exchange resins commonly have a single functionality for either cations or anions. Resins that have a dual functionality for both cations and anions are uncommon. The objective of this study was to create dual-functional ion exchange resins derived from soybean hulls, sugarcane bagasse and corn stover. Dual-functional resins were prepared by two separate two-step processes. In the first two-step process, by-products were reacted with a solution of citric acid in order to impart additional negative charge, and then reacted with the cross-linking reagent dimethyloldihydroxyethylene urea (DMDHEU) and a quaternary amine (choline chloride) to add positive charge to the lignocellulosic material. In the second two-step process, the order of reaction was reversed, with positive charge added first, followed by the addition of negative charge. These combined reactions added both cationic and anionic character to the by-products as evidenced by the increased removal from solution of copper (Cu(2+)) cation and the chromate (CrO(4)(2-)) anion compared to unmodified by-products. The order of reaction appeared to slightly favor the functionality that was added last. That is, if negative charge was added last, the resulting resin sequestered more copper ion than a comparable resin where the negative charge was added first and vice-versa. Cu(2+) and CrO(4)(2-) were used as marker ions in a solution that contained both competing cations and anions. The dual-functional resins adsorbed as much as or more of the marker ions compared to commercial cation or anion exchange resins used for comparison. None of the commercial resins exhibited dual-functional properties to the same extent as the by-product-based resins.
离子交换树脂通常对阳离子或阴离子具有单一功能。对阳离子和阴离子都具有双重功能的树脂并不常见。本研究的目的是制备源自大豆壳、甘蔗渣和玉米秸秆的双功能离子交换树脂。双功能树脂通过两个独立的两步法制备。在第一个两步法中，副产物与柠檬酸溶液反应以赋予额外的负电荷，然后与交联剂二羟甲基二羟基乙烯脲（DMDHEU）和季胺（氯化胆碱）反应，向木质纤维素材料添加正电荷。在第二个两步法中，反应顺序相反，先添加正电荷，然后添加负电荷。这些组合反应赋予了副产物阳离子和阴离子特性，与未改性的副产物相比，从溶液中去除铜（Cu(2+)）阳离子和铬酸根（CrO(4)(2-)）阴离子的量增加证明了这一点。反应顺序似乎略微有利于最后添加的功能。也就是说，如果最后添加负电荷，所得树脂比首先添加负电荷的可比树脂能螯合更多的铜离子，反之亦然。在同时含有竞争性阳离子和阴离子的溶液中，使用Cu(2+)和CrO(4)(2-)作为标记离子。与用于比较的商业阳离子或阴离子交换树脂相比，双功能树脂吸附的标记离子量相同或更多。没有一种商业树脂表现出与基于副产物的树脂相同程度的双功能特性。
