Contributions of Nanoscale Roughness to Anomalous Colloid Retention and Stability Behavior
Contributions of Nanoscale Roughness to Anomalous Colloid Retention and Stability Behavior
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DOI：
10.1021/acs.langmuir.7b02445
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发表时间：
2017-09-26
期刊：
影响因子：
3.9
通讯作者：
Shang, Jianying
中科院分区：
文献类型：
--
作者：
Bradford, Scott A.;Kim, Hyunjung;Shang, Jianying
所有自然表面都表现出一定程度的纳米级粗糙度（NR）和化学不均匀性（CH）。表达式被开发来确定胶体和固体水界面之间的平均相互作用能，以及胶体胶体相互作用，当两个表面都包含二元NR和CH。然后研究了异质性类型，粗糙度参数，溶液离子强度（IS），平均zeta电位和胶体尺寸对预测的相互作用能分布的影响。CH的作用增强了光滑表面上的CH量较大，特别是对于较小的胶体和较高的IS。然而，预测的相互作用能分布主要由NR，这往往会降低能量势垒高度和幅度的二级和初级最小值，特别是当粗糙度分数是小的。这大大增加了净静电不利表面上初级与次级最小值相互作用的相对重要性，特别是当两个表面上都出现粗糙度时以及对于产生小能量势垒的条件（例如，更高的IS、更低的pH、更低的ζ电位值，以及更小的胶体尺寸）。粗糙度和玻恩排斥的综合影响经常产生一个浅的初级最小值，即使在静电有利的条件下，也容易受到动能随机变化的扩散去除。使用测量的zeta电位和假设的粗糙度特性进行的计算表明，粗糙度为许多以前归因于电空间排斥的实验偏差提供了可行的替代解释（例如，随着溶液IS的增加，胶体保留减少;在有利条件下可逆的胶体保留;以及由于吸附的表面活性剂、聚合物和/或腐殖物质而减少的胶体保留和增强的胶体稳定性）。
All natural surfaces exhibit nanoscale roughness (NR) and chemical heterogeneity (CH) to some extent. Expressions were developed to determine the mean interaction energy between a colloid and a solid water interface, as well as for colloid colloid interactions, when both surfaces contain binary NR and CH. The influence of heterogeneity type, roughness parameters, solution ionic strength (IS), mean zeta potential, and colloid size on predicted interaction energy profiles was then investigated. The role of CH was enhanced on smooth surfaces with larger amounts of CH, especially for smaller colloids and higher IS. However, predicted interaction energy profiles were mainly dominated by NR, which tended to lower the energy barrier height and the magnitudes of both the secondary and primary minima, especially when the roughness fraction was small. This dramatically increased the relative importance of primary to secondary minima interactions on net electrostatically unfavorable surfaces, especially when roughness occurred on both surfaces and for conditions that produced small energy barriers (e.g., higher IS, lower pH, lower magnitudes in the zeta potential, and for smaller colloid sizes) on smooth surfaces. The combined influence of roughness and Born repulsion frequently produced a shallow primary minimum that was susceptible to diffusive removal by random variations in kinetic energy, even under electrostatically favorable conditions. Calculations using measured zeta potentials and hypothetical roughness properties demonstrated that roughness provided a viable alternative explanation for many experimental deviations that have previously been attributed to electrosteric repulsion (e.g., a decrease in colloid retention with an increase in solution IS; reversible colloid retention under favorable conditions; and diminished colloid retention and enhanced colloid stability due to adsorbed surfactants, polymers, and/or humic materials).