Viscoelastic gels of guar and xanthan gum mixtures provide long-term stabilization of iron micro- and nanoparticles
Viscoelastic gels of guar and xanthan gum mixtures provide long-term stabilization of iron micro- and nanoparticles
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DOI：
10.1007/s11051-012-1239-0
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发表时间：
2012-11-01
影响因子：
2.5
通讯作者：
Sethi, Rajandrea
中科院分区：
文献类型：
--
作者：
Xue, Dingqi;Sethi, Rajandrea
用于地下水修复和医疗应用的铁微米和纳米颗粒易于快速聚集和沉积。瓜尔胶（GG）或黄原胶（XG）的稀释的单一生物聚合物水溶液可以稳定这些颗粒几个小时，提供空间排斥并通过增加悬浮液的粘度。该研究的目的是证明用少量XG（XG/GG重量比1：19;总生物聚合物浓度为3g/L）修改GG溶液可以显著提高生物聚合物稳定高浓度铁微颗粒和纳米颗粒悬浮液的能力。GG和XG之间的协同效应产生粘弹性凝胶，其可以保持20 g/L的铁颗粒悬浮超过24 h。这归因于（i）静态粘度的增加，（ii）组合的聚合物结构，其屈服应力与由铁颗粒施加的向下应力形成对比，以及（iii）聚合物吸附到铁表面，对颗粒具有锚定作用。XG/GG粘弹性凝胶具有明显的剪切变稀行为。这种性质，加上低生物聚合物浓度，决定了在高剪切速率下的小粘度值，促进了多孔介质中的注入。此外，软弹性聚合物网络的热敏性促进了在低温下更高的稳定性和更长的储存时间以及在较高温度下粘度的快速降低。可以利用该特征以改善悬浮液的流动性和向目标的递送，以及有效地调节和控制铁颗粒的释放。
Iron micro- and nanoparticles used for groundwater remediation and medical applications are prone to fast aggregation and sedimentation. Diluted single biopolymer water solutions of guar gum (GG) or xanthan gum (XG) can stabilize these particles for few hours providing steric repulsion and by increasing the viscosity of the suspension. The goal of the study is to demonstrate that amending GG solutions with small amounts of XG(XG/GG weight ratio 1: 19; 3 g/Lof total biopolymer concentration) can significantly improve the capability of the biopolymer to stabilize highly concentrated iron micro-and nanoparticle suspensions. The synergistic effect between GG and XG generates a viscoelastic gel that can maintain 20 g/L iron particles suspended for over 24 h. This is attributed to (i) an increase in the static viscosity, (ii) a combined polymer structure the yield stress of which contrasts the downward stress exerted by the iron particles, and (iii) the adsorption of the polymers to the iron surface having an anchoring effect on the particles. The XG/GG viscoelastic gel is characterized by a marked shear thinning behavior. This property, coupled with the low biopolymer concentration, determines small viscosity values at high shear rates, facilitating the injection in porous media. Furthermore, the thermosensitivity of the soft elastic polymeric network promotes higher stability and longer storage times at low temperatures and rapid decrease of viscosity at higher temperatures. This feature can be exploited in order to improve the flowability and the delivery of the suspensions to the target as well as to effectively tune and control the release of the iron particles.