有机质和阳离子对氧化石墨烯团聚行为的影响

利用动态光散射技术分别考察了3种天然有机质（NOM）及其浓度和阳离子对纳米氧化石墨烯（GO）在水环境中团聚动力学的影响.无NOM存在时，GO团聚行为符合经典的Derjaguin-Landau-Verwey-Overbeek（DLVO）理论和舒尔采-哈迪准则.Na⁺溶液中，NOM显著增强GO稳定性，顺序为腐殖酸（HA） > 富里酸（FA） > 海藻酸钠（SA），这主要是由于HA在GO之间产生了更强的空间位阻斥力.以HA为代表性有机质，2mg/L HA对GO在水溶液中的稳定性还受阳离子种类的影响：HA增强了GO在Na⁺和Mg²⁺溶液中的稳定性，然而对GO在Ca²⁺溶液中的稳定性几乎没有影响.提高HA浓度为5mg/L时：高浓度Mg²⁺溶液中，HA的盐析效应使得其未促进GO稳定性；Ca²⁺溶液中，HA与Ca²⁺发生了较强的桥联作用，使得HA促进了GO的团聚.

Impacts of natural organic matter and electrolytes on aggregation kinetics of graphene oxide

In this study,the impacts of three typical natural organic matters (NOMs:humic acid (HA),fulvic acid (FA) and sodium alginate (SA)) at different concentrations (2 and 5mg/L,total organic carbon,TOC) and electrolyte types (Na⁺,Mg²⁺,Ca²⁺) on the aggregation kinetics of graphene oxide (GO) nanoparticles were investigated through dynamic light scattering.The GO aggregation kinetics without NOM followed the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) model and Schulze-Hardy rule.All the three NOMs at 2mg/L enhanced the stability of GO in the order of HA > FA > SA,which could be due to the strongest steric repulsive force exhibited by HA than FA and SA in the presence of Na⁺.In the presence of 2mg/L HA,which was selected as the representative NOM,it significantly enhanced the stability of GO in the solutions of Na⁺ and Mg²⁺;while it displayed marginal influence for Ca²⁺.When the HA concentration increased to 5mg/L,it did not further enhance the stability of GO in the solution of high concentration Mg²⁺ due to salting out effect of HA;while it depressed GO stability in the solution of Ca²⁺ with higher attachment efficiencies than the control experiment in the absence of any NOM.