Barakat Mohamed Abou Elfetouh, Kumar Rajeev, Seliem Moaaz Korany, Selim Ali Qurany, Mobarak Mohamed, Anastopoulos Ioannis, Giannakoudakis Dimitrios, Barczak Mariusz, Bonilla-Petriciolet Adrián, Mohamed Essam Abdelrahman
Department of Environmental Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
Central Metallurgical R & D Institute, Helwan 11421, Cairo, Egypt.
Nanomaterials (Basel). 2020 Jul 24;10(8):1454. doi: 10.3390/nano10081454.
Surfactant-modified exfoliated Fayum clay (CTAB-EC) obtained after chemical treatment with a CTAB/HO solution was further decorated with magnetic FeO nanoparticles (MNP). The final nanocomposite (MNP/CTAB-EC) was characterized by XRD, SEM, FTIR, TEM and its adsorptive capability against a model cationic dye, crystal violet (CV), was evaluated. A comparison of the adsorption performance of the raw clay and its modified counterparts using HO, CTAB, CTAB/HO or MNP indicated that the adsorption capacity of MNP/CTAB-EC was the highest for CV removal at pH 8.0. The pseudo‒second order for the kinetics and Freundlich model for adsorption equilibrium fitted well the CV removal experimental data at all tested temperatures (25, 40 and 55 °C). The enhancement of the Langmuir adsorption capacity from 447.1 to 499.4 mg g with increasing the temperature from 25 to 55 °C revealed an endothermic nature of the removal process. The interactions between CV and MNP/CTAB-EC were interpreted using advanced statistical physics models (ASPM) in order to elucidate the adsorption mechanism. Multilayer model fitted the adsorption process and therefore, the steric and energetic factors that impacted the CV adsorption were also interpreted using this model. The aggregated number of CV molecules per MNP/CTAB-EC active site ( n ) was more than unity at all temperatures, representing thus a vertical adsorption orientation and a multi‒interactions mechanism. It was determined that the increase of CV uptake with temperature was mainly controlled by the increase of the number of active sites (). Calculated adsorption energies (Δ) revealed that CV removal was an endothermic and a physisorption process (Δ < 40 kJ mol ). MNP/CTAB-EC was magnetically separated, regenerated by NaOH, and reused without significant decrease in its adsorption efficiency, supporting a prosperity of its utilization as an effective adsorbent against hazardous dyes from wastewaters.
用十六烷基三甲基溴化铵/水（CTAB/HO）溶液进行化学处理后得到的表面活性剂改性剥离法尤姆黏土（CTAB-EC），进一步用磁性Fe₃O₄纳米颗粒（MNP）进行修饰。最终的纳米复合材料（MNP/CTAB-EC）通过X射线衍射（XRD）、扫描电子显微镜（SEM）、傅里叶变换红外光谱（FTIR）、透射电子显微镜（TEM）进行表征，并评估了其对模型阳离子染料结晶紫（CV）的吸附能力。对未改性黏土及其用HO、CTAB、CTAB/HO或MNP改性后的对应物的吸附性能进行比较，结果表明，在pH为8.0时，MNP/CTAB-EC对CV的去除吸附容量最高。在所有测试温度（25、40和55℃）下，动力学的准二级模型和吸附平衡的弗伦德利希模型都很好地拟合了CV去除实验数据。随着温度从 25℃升高到55℃，朗缪尔吸附容量从447.1 mg/g提高到499.4 mg/g，这表明去除过程具有吸热性质。为了阐明吸附机制，使用高级统计物理模型（ASPM）解释了CV与MNP/CTAB-EC之间的相互作用。多层模型拟合了吸附过程，因此，还使用该模型解释了影响CV吸附的空间位阻和能量因素。在所有温度下，每个MNP/CTAB-EC活性位点上CV分子的聚集数（n）都大于1，因此代表垂直吸附取向和多相互作用机制。确定随着温度升高CV吸附量的增加主要受活性位点数量增加的控制。计算得到的吸附能（Δ）表明，CV去除是一个吸热的物理吸附过程（Δ<40kJ/mol）。MNP/CTAB-EC通过磁性分离，用NaOH再生，并在吸附效率没有显著降低的情况下重复使用，这支持了其作为废水中有害染料的有效吸附剂的应用前景。
