School of Environmental Engineering, Technical University of Crete, 73100 Chania, Greece.
School of Environmental Engineering, Technical University of Crete, 73100 Chania, Greece.
Sci Total Environ. 2017 Feb 1;579:736-744. doi: 10.1016/j.scitotenv.2016.11.034. Epub 2016 Nov 22.
Graphene oxide (GO) is a material with rapid production growth, and consequently GO nanoparticles are expected to eventually penetrate subsurface formations, where fine mineral particles are in abundance. This study examines the heteroaggregation of GO nanoparticles with kaolinite (KGa-1b) colloids under various conditions. Dynamic batch experiments were conducted in solutions with different pH values (pH=4, 7, and 10), different ionic strengths (I=7, 12, and 27mM), and at three controlled temperatures (8, 14, and 25°C). The experimental results showed that a relatively small amount of GO nanoparticles (5-20% of the initial concentration) attached immediately onto KGa-1b colloids, and reached equilibrium in <20min. It was shown that neither temperature nor pH played a significant role in the attachment of GO nanoparticles onto KGa-1b colloids. In contrast, the attachment of GO nanoparticles onto KGa-1b colloids was shown to increase with increasing I. Additionally, time-resolved dynamic light scattering (DLS) was used to identify the influence of I on heteroaggregation between GO nanoparticles and KGa-1b colloids. The critical coagulation concentration (CCC) for the interaction between GO nanoparticles and KGa-1b colloids was 152mM (NaCl). The interaction energies were calculated, for all experimental conditions, by using measured zeta potentials and applying the classical DLVO theory. The equilibrium experimental data were fitted with a Freundlich isotherm, and the attachment kinetics were described very well with a pseudo-second-order model. Furthermore, thermodynamic analysis revealed that the attachment process was nonspontaneous and exothermic.
氧化石墨烯（GO）是一种产量快速增长的材料，预计最终将渗透到地下地层中，那里有丰富的细矿物颗粒。本研究考察了不同条件下 GO 纳米颗粒与高岭石（KGa-1b）胶体的异质聚集。在不同 pH 值（pH=4、7 和 10）、不同离子强度（I=7、12 和 27mM）和三个控制温度（8、14 和 25°C）的溶液中进行了动态批量实验。实验结果表明，少量 GO 纳米颗粒（初始浓度的 5-20%）立即附着在 KGa-1b 胶体上，并在<20min 内达到平衡。结果表明，温度和 pH 值都没有显著影响 GO 纳米颗粒在 KGa-1b 胶体上的附着。相比之下，GO 纳米颗粒在 KGa-1b 胶体上的附着随着 I 的增加而增加。此外，还使用时间分辨动态光散射（DLS）来确定 I 对 GO 纳米颗粒和 KGa-1b 胶体之间异质聚集的影响。GO 纳米颗粒和 KGa-1b 胶体之间相互作用的临界聚沉浓度（CCC）为 152mM（NaCl）。根据测量的动电电位并应用经典 DLVO 理论，计算了所有实验条件下的相互作用能。通过 Freundlich 等温线拟合平衡实验数据，并用准二级模型很好地描述了附着动力学。此外，热力学分析表明，附着过程是非自发的和放热的。
