Department of Chemistry, Faculty of Sciences, University of Neyshabur, Neyshabur, Iran.
Department of Civil Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.
Environ Sci Pollut Res Int. 2020 Dec;27(35):43999-44021. doi: 10.1007/s11356-020-10175-7. Epub 2020 Aug 3.
In this paper, folic acid-coated graphene oxide nanocomposite (FA-GO) is used as an adsorbent for the treatment of heavy metals including cadmium (Cd) and copper (Cu) ions. As such, graphene oxide (GO) is modified by folic acid (FA) to synthesize FA-GO nanocomposite and characterized by the atomic force microscopy (AFM), Fourier transform-infrared (FT-IR) spectrophotometry, scanning electron microscopy (SEM), and C/H/N elemental analyses. Also, computational intelligence tests are used to study the mechanism of the interaction of FA molecules with GO. Based on the results, FA molecules formed a strong π-π stacking, chemical, and hydrogen bond interactions with functional groups of GO. Main parameters including pH of the sample solution, amounts of adsorbent, and contact time are studied and optimized by the Response Surface Methodology Based on Central Composite Design (RSM-CCD). In this study, the equilibrium of adsorption is appraised by two (Langmuir and Freundlich and Temkin and D-R models) and three parameter (Sips, Toth, and Khan models) isotherms. Based on the two parameter evaluations, Langmuir and Freundlich models have high accuracy according to the R coefficient (more than 0.9) in experimental curve fittings of each pollutant adsorption. But, multilayer adsorption of each contaminant onto the FA-GO adsorbent (Freundlich equation) is demonstrated by three parameter isotherm analysis. Also, isotherm calculations express maximum computational adsorption capacities of 103.1 and 116.3 mg g for Cd and Cu ions, correspondingly. Kinetic models are scrutinized and the outcomes depict the adsorption of both Cd and Cu followed by the pseudo-second-order equation. Meanwhile, the results of the geometric model illustrate that the variation of adsorption and desorption rates do not have any interfering during the adsorption process. Finally, thermodynamic studies show that the adsorption of Cu and Cd onto the FA-GO nanocomposite is an endothermic and spontaneous process.
本文使用叶酸包覆的氧化石墨烯纳米复合材料（FA-GO）作为吸附剂来处理包括镉（Cd）和铜（Cu）离子在内的重金属。因此，通过叶酸（FA）对氧化石墨烯（GO）进行改性，合成 FA-GO 纳米复合材料，并通过原子力显微镜（AFM）、傅里叶变换红外（FT-IR）分光光度法、扫描电子显微镜（SEM）和 C/H/N 元素分析进行表征。此外，还使用计算智能测试来研究 FA 分子与 GO 相互作用的机制。结果表明，FA 分子与 GO 的官能团形成了强烈的π-π堆积、化学和氢键相互作用。通过基于中心复合设计的响应面法（RSM-CCD）研究并优化了主要参数，包括样品溶液的 pH 值、吸附剂的用量和接触时间。在本研究中，通过两种（Langmuir 和 Freundlich 以及 Temkin 和 D-R 模型）和三种参数（Sips、Toth 和 Khan 模型）等温线来评价吸附平衡。根据每种污染物吸附实验曲线拟合的 R 系数（大于 0.9），两种参数评价表明 Langmuir 和 Freundlich 模型具有较高的准确性。但通过三参数等温线分析，表明每个污染物在 FA-GO 吸附剂上的多层吸附（Freundlich 方程）。此外，等温线计算表明 Cd 和 Cu 离子的最大计算吸附容量分别为 103.1 和 116.3mg/g。对动力学模型进行了仔细研究，结果表明，Cd 和 Cu 的吸附都遵循准二级方程。同时，几何模型的结果表明，在吸附过程中，吸附和脱附速率的变化没有任何干扰。最后，热力学研究表明，Cu 和 Cd 在 FA-GO 纳米复合材料上的吸附是一个吸热和自发的过程。
