有机质和阳离子对氧化石墨烯团聚行为的影响

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

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Mg^(2+)溶液中的稳定性,然而对GO在Ca^(2+)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Mg^(2+)溶液中,HA的盐析效应使得其未促进GO稳定性;Ca^(2+)溶液中,HA与Ca^(2+)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） andsodium 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 lightscattering. 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 ofHA〉FA〉SA, which could be due to the strongest steric repulsive force exhibited by HA than FA and SA in the presence ofNa＋. In the presence of 2mg/L HA, which was selected as the representative NOM, it significantly enhanced the stabilityof GO in the solutions of Na＋ and Mg2＋; while it displayed marginal influence for Ca2＋. When the HA concentrationincreased to 5mg/L, it did not further enhance the stability of GO in the solution of high concentration Mg2＋ due to saltingout effect of HA; while it depressed GO stability in the solution of Ca2＋ with higher attachment efficiencies than thecontrol experiment in the absence of any NOM.