Laboratory for Advanced Carbon Nanomaterials, Kazan Federal University, Kremlyovskaya str. 18, Kazan 420008, Russian Federation.
Laboratory for Advanced Carbon Nanomaterials, Kazan Federal University, Kremlyovskaya str. 18, Kazan 420008, Russian Federation.
J Colloid Interface Sci. 2018 Oct 1;527:222-229. doi: 10.1016/j.jcis.2018.05.044. Epub 2018 May 17.
Graphene oxide (GO) have emerged recently as a novel material for sorbing metal cations from aqueous media. However, the literature data on sorption capacity differ by more than one order in magnitude, and the nature of the chemical bonding between GO and metal cations remains unclear. In this work we show that Gd ions are bound to GO by both coordinate-covalent bonding and electrostatic attraction with prevailing the former. We provide the complete account for the GO sorption toward Gd as the function of the Gd/GO ratio and pH of solution. The upper limits of the strong bonding are determined as 0.70 and 0.16 mmol(Gd)/g(GO) in the neutral and in the intrinsically acidic solutions, respectively. At large excess of Gd in the neutral solutions, the sorption capacity reaches 1.45 mmol(Gd)/g(GO). The effectiveness of water, hydrochloric acid and EDTA as desorbing eluents is compared. We experimentally demonstrate the existence of the Gd concentration gradient within the diffuse layer at the GO/water interface, and its exponential character on the distance from the GO surface. The thickness of the diffuse layer and the position of the slipping plane are estimated. Such characteristics, typical for colloid systems, show that in solutions, GO flakes form distinct phase, even though they are just one atom thick.
氧化石墨烯（GO）最近作为一种新型材料，从水介质中吸附金属阳离子。然而，关于吸附容量的文献数据相差一个数量级以上，并且 GO 与金属阳离子之间的化学键的性质仍不清楚。在这项工作中，我们表明 Gd 离子通过配位共价键和静电吸引与 GO 结合，前者占主导地位。我们提供了完整的 GO 对 Gd 的吸附情况，作为 Gd/GO 比和溶液 pH 值的函数。在中性和固有酸性溶液中，强键的上限分别确定为 0.70 和 0.16 mmol(Gd)/g(GO)。在中性溶液中 Gd 大量过剩时，吸附容量达到 1.45 mmol(Gd)/g(GO)。比较了水、盐酸和 EDTA 作为解吸洗脱剂的效果。我们实验证明了在 GO/水界面的扩散层内存在 Gd 浓度梯度，并且该梯度在距 GO 表面的距离上具有指数特征。扩散层的厚度和滑移面的位置被估计。这些胶体系统的典型特征表明，在溶液中，GO 薄片即使只有一个原子厚，也会形成明显的相。
