Novel composite hydrogels containing fractionated, purified lignins for aqueous-based separations
Novel composite hydrogels containing fractionated, purified lignins for aqueous-based separations
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DOI：
10.1039/d0ta09046h
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发表时间：
2021-01-14
影响因子：
11.9
通讯作者：
Davis, Eric M.
中科院分区：
文献类型：
--
作者：
Gregorich, Nicholas;Ding, Junhuan;Davis, Eric M.
在此，一系列新的，基于木质素的水凝胶复合材料的制备通过将超净木质素（UCL），控制分子量和低分散性，到聚（乙烯醇）（PVA）。UCL是从一种新的液-液分馏的高分散性粗散装木质素（CBL）从硫酸盐法造纸黑液获得。使用这些CBL制备了一系列互补的复合水凝胶。CBL和UCL都用含乙烯基的丙烯酸酯基团官能化，允许木质素与自身化学交联，与PVA链的热交联网络形成互穿网络。通过质子和磷核磁共振证实了UCL的成功官能化。与纯PVA相比，含有20重量% UCL的PVA-木质素水凝胶的亚甲基蓝（MB）渗透性降低了约两个数量级。此外，对于含有50重量% UCL或CBL的复合水凝胶，在渗透实验的持续时间内在接收储层中没有检测到MB。通常，在含有CBL的PVA-木质素水凝胶中观察到杨氏模量的增加，其中当与纯PVA相比时，由50重量%CBL组成的水凝胶表现出类似于40%的增加。相比之下，对于含有20重量%UCL或更少的复合水凝胶，观察到杨氏模量类似于10%的降低，尽管这些膜在所有研究的膜中表现出最低的MB渗透性。然而，对于含有50重量%UCL的复合水凝胶观察到膜刚度的最大增加，其中观察到杨氏模量增加了70%。最后，木质素的浓度和官能化被认为对软复合材料的网络结构有直接影响，其中通常，交联之间的分子量随着木质素浓度的增加而降低。
Herein, a series of novel, lignin-based hydrogel composites was fabricated by incorporating ultraclean lignins (UCLs), of controlled molecular weight and low dispersity, into poly(vinyl alcohol) (PVA). The UCLs were obtained from a novel liquid-liquid fractionation of high dispersity crude bulk lignins (CBLs) obtained from Kraft black liquor. A complementary series of composite hydrogels was fabricated using these CBLs. Both the CBLs and UCLs were functionalized with vinyl-containing acrylate groups allowing the lignins to chemically crosslink with themselves, forming an interpenetrated network with the thermally-crosslinked network of PVA chains. Successful functionalization of the UCLs was demonstrated by proton and phosphorous nuclear magnetic resonance. PVA-lignin hydrogels containing 20 wt% UCL saw a reduction in methylene blue (MB) permeability by approximately two orders of magnitude when compared to neat PVA. Further, for composite hydrogels containing either 50 wt% UCL or CBL, no MB was detected in the receiving reservoir over the duration of the permeation experiment. In general, an increase in Young's moduli was observed in PVA-lignin hydrogels containing CBLs, where hydrogels composed of 50 wt% CBLs exhibited similar to 40% increase when compared to neat PVA. In contrast, a similar to 10% reduction in Young's moduli was observed for composite hydrogels containing 20 wt% UCLs or less, though these membranes exhibited the lowest MB permeabilities of all membranes investigated. However, the largest increase in membrane stiffness was observed for composite hydrogels containing 50 wt% UCLs, where a similar to 70% increase in Young's modulus was observed. Finally, the concentration and functionalization of the lignins was seen to have a direct impact on the network structure of the soft composites, where in general, the molecular weight between crosslinks is seen to decrease with increasing lignin concentration.