Abstract:

This study was conducted on one-dimensional seepage in saturated porous media fixed on packed bed columns to investigate the fate of graphene oxide (GO) in the subsurface environment. In the present experiments, the fate of grapheme oxide (GO) was investigated as a function of cations composition (sodium absorption ratios, SAR) at 10 mmol·L^-1 constant ionic strength (IS). To analyze the migration deposition mechanism of GO, the deposition kinetics curve was determined by mathematical model and interface chemistry theory. When SAR increased from zero to ∞, maximum effluent concentration of sand columns and recovery of GO increased, however, deposition rate, removal efficiency and attachment efficiency of the breakthrough experiments decreased respectively from 0.356 min^-1 to 0.039 min^-1 、1.04×10^-2 to 1.1×10^-3 and 0.054 to 0.003. Accordingly, it was proposed that Brownian diffusion was the major mechanism which resulted in contacting between GO particles and quartz sand particles, and the change of Ca²⁺ concentration was the predominant factor which caused GO different migration behavior at different SAR. The charge neutralization and bridging between Ca²⁺ and GO could be responsible for the balance of electrostatic repulsion and attraction between the particles, which affected the size and shape of GO particles and strengthened the retention effect of sand column on GO.

Key words: graphene oxide, particle, cations composition, porous media, particle transport, model

摘要：

采用室内饱和石英砂柱一维渗流模拟实验,研究离子强度相同、离子组成(钠吸附比)不同的电解质溶液对氧化石墨烯(GO)在地下环境中迁移行为的影响。通过测定GO穿透过程的沉积动力学曲线,结合数学模型与界面化学理论,对其迁移沉积机理进行分析。结果显示,当钠吸附比从0增加到∞时,砂柱出流最大浓度升高,GO回收率增加,穿透实验沉积速率、去除效率和吸附效率分别从0.356 min^-1、1.04×10^-2、0.054减小到0.039 min^-1、1.1×10^-3、0.003。研究认为布朗扩散是造成GO颗粒与石英砂粒相互接触的主要机制,Ca²⁺浓度变化是造成不同钠吸附比环境下GO不同迁移行为的主要因素,其机理在于Ca²⁺与GO发生电中和与桥接作用,改变了颗粒间的静电斥力与引力平衡,进而影响了GO颗粒粒度与形态,并最终强化了砂柱对GO的截留效应。

关键词: 氧化石墨烯, 粒子, 离子组成, 多孔介质, 迁移行为, 模型