Ethylene diaminetetraacetic acid (EDTA)-functionalized graphene was synthesized from Nigerian coal using a chemical exfoliation method and the graphene was applied for the removal of Congo red dye from aqueous solutions. The synthesized coal graphene and the raw coal were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM)–energy-dispersive X-ray (EDX) spectroscopy, measurement of pHpzc (pH of point of zero charge), and Boehm titrations. The SEM data revealed surface roughness which is enhanced in the prepared graphene while the EDX revealed an increase in carbon content, the main constituent of graphene, from about 26% in the raw coal to about 80% in the prepared graphene. Various adsorption variables, such as pH, contact time, concentration of Congo red, and temperature, were varied for the removal of the dye using raw coal and the synthesized coal graphene. The Liu isotherm gave the best fit of the equilibrium data than the Langmuir, Freundlich, and Dubinin-Radushkevich models. The maximum adsorption capacities of the raw coal and synthesized coal graphene at 25°C are 109.1 mg/g and 129.0 mg/g, respectively. The Avrami fractional-order kinetic model was the best model for description of the kinetic data. The model had the lowest values of standard deviation than the pseudo-first-order and pseudo-second-order models. The adsorption process of the two materials occurred via two stages as proved by intraparticle diffusion model. The adsorption process of the Congo red removal was spontaneous, feasible, and endothermic. The study conclusively revealed the graphene nanomaterial to be a viable adsorbent for textile wastewater treatment.

使用化学剥离法从尼日利亚煤中合成乙二胺四乙酸 (EDTA) 功能化石墨烯，并将石墨烯用于从水溶液中去除刚果红染料。使用傅里叶变换红外 (FTIR) 光谱、X 射线衍射 (XRD) 光谱、扫描电子显微镜 (SEM)-能量色散 X 射线 (EDX) 光谱、pHpzc测量对合成的煤石墨烯和原煤进行表征（零电荷点的 pH 值）和 Boehm 滴定。SEM 数据显示制备的石墨烯中表面粗糙度增强，而 EDX 显示石墨烯的主要成分碳含量从原煤中的约 26% 增加到制备的石墨烯中的约 80%。使用原煤和合成的煤石墨烯去除染料时，各种吸附变量，如 pH 值、接触时间、刚果红浓度和温度，都会发生变化。与 Langmuir、Freundlich 和 Dubinin-Radushkevich 模型相比，Liu 等温线给出了平衡数据的最佳拟合。原煤和合成煤石墨烯在 25°C 下的最大吸附容量分别为 109.1 mg/g 和 129.0 mg/g。Avrami 分数阶动力学模型是描述动力学数据的最佳模型。该模型的标准偏差值低于伪一阶和伪二阶模型。颗粒内扩散模型证明两种材料的吸附过程分两个阶段进行。去除刚果红的吸附过程是自发的、可行的和吸热的。该研究最终表明石墨烯纳米材料是一种可行的纺织废水处理吸附剂。