有机质和阳离子对氧化石墨烯团聚行为的影响

摘要

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.%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.