氧化石墨阳离子交换容量测定过程中结构的变化

氧化石墨(GO)结构层上的碳羟基(―C―OH)和边缘羧基(―COOH)在水介质中发生质子化反应解离出的H+具有阳离子可交换性。实验采用甲醛缩合法测量了GO的阳离子交换容量(CEC),用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和X射线光电子能谱(XPS)分析测试手段对GO阳离子交换过程中间产物的结构变化进行了分析。结果表明,GO的CEC高达541.48 mmol/100 g。NH_4~+和Ca~(2+)交换后的GO,保持稳定的层状结构,c轴方向层间距分别增大了0.1499和0.2905 nm。NH_4+和Ca~(2+)主要以层间可交换阳离子形式存在于层间域中,并与水分子形成可交换水化阳离子层,部分以NH_4(H_2O)_6]+和Ca(H_2O)_6]_2+的形式存在于结构层的边缘附近,共同平衡结构层水解产生的负电荷。

Structure Development during the Cation Exchange Processes of Graphite Oxide

Oxygen-containing hydroxyl (-C-OH) and carboxyl (-COOH) functional groups on both the basal planes and edges of the graphite oxide (GO) structure can dissociate to form H⁺ in water, thus providing cation exchange ability. The cation exchange capacity (CEC) of GO was measured accurately using the Stiasny method and the intermediate products of cation exchange processes of oxygen-containing functional groups and structure development were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results indicated that the CEC of GO was up to 541.48 mmol/100 g. After NH₄⁺ and Ca²⁺ exchange processes, GO still maintained a stable lamellar structure, and the c axis spacing increased by 0.1499 and 0.2905 nm, respectively. NH₄⁺ and Ca²⁺ were mainly in the form of exchangeable cations in the interlayer space of GO, and formed a hydrated cation layer with water molecules, part of the containingNH₄(H₂O)₆]⁺ orCa(H₂O)₆]²⁺ formed near the edge of the structural layer, balancing the negative charges originating from hydrolysis of the carboxyl groups of the GO structural layer.