The Strengthening Role of the Amino Group in Metal-Organic Framework MIL-53 (Al) for Methylene Blue and Malachite Green Dye Adsorption
The Strengthening Role of the Amino Group in Metal-Organic Framework MIL-53 (Al) for Methylene Blue and Malachite Green Dye Adsorption
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DOI：
10.1021/acs.jced.5b00692
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发表时间：
2015-11-01
期刊：
影响因子：
--
通讯作者：
Wu, Chunsheng
中科院分区：
文献类型：
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作者：
Li, Chen;Xiong, Zhenhu;Wu, Chunsheng
本文合成了MIL-53（Al）和MIL-53(Al)-NH2两种金属有机骨架（mof）。然后用这些MOFs去除水溶液中的亚甲基蓝和孔雀石绿染料。采用x射线粉末衍射（XRD）、扫描电镜（SEM）、傅里叶变换红外光谱（FT-IR）和zeta电位对mof进行了表征。实验结果表明，MIL-53(Al)-NH2能快速结合水溶液中的两种阳离子染料，具有较高的吸附能力。但MIL-53（Al）对阳离子染料的吸附能力极低。MIL-53(Al)-NH2对阳离子染料的选择性吸附是由于染料分子的氨基基与MIL-53(Al)-NH2之间的氢键相互作用所致，而MIL-53(Al)-NH2对染料的极低吸附量可能主要是由于MIL-53（Al）的“呼吸”行为所致。研究了吸附时间、温度、溶液pH等因素对两种染料在MIL-53(Al)-NH2上吸附的影响。采用拟一级动力学模型、拟二级动力学模型和Weber Morris模型拟合吸附数据，拟二级动力学模型比拟一级动力学模型更适合亚甲基蓝和孔雀石绿的吸附。以Weber-Morris模型为代表的内扩散模型参与了速度控制步骤，但并不是唯一的速度控制步骤，外扩散在吸附过程中也起着重要作用。研究了亚甲基蓝和孔雀石绿在MIL-53(Al)-NH2上的吸附等温线和热力学。MIL-53(Al)-NH2对亚甲基蓝和孔雀石绿染料的吸附均符合Langmuir等温线和Freundlich等温线，但前者的吸附效果优于后者。吸附热力学实验表明，吸附反应是自发的、吸热的。最后，根据实验现象，提出了可能的吸附机理。此外，使用过的吸附剂可以重复使用，通过简单的洗涤进行吸附去除。
In this paper, two kinds of metal organic frameworks (MOFs), MIL-53(Al) and MIL-53(Al)-NH2, were synthesized. Then these MOFs were used to remove methylene blue and malachite green dyes from aqueous solution. Characterizations of MOFs were carried out by X-ray powder diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectrometry, and zeta potential. Experimental results showed that MIL-53(Al)-NH2 can rapidly bind to the two kinds of cationic dyes from aqueous solution with high adsorption capacity. However, the adsorption capacity of MIL-53(Al) for cationic dyes is extremely low. The adsorptive selectivity of MIL-53(Al)-NH2 to the cationic dyes resulted from the hydrogen bonding interaction between amimo groups of the dyes molecule and the MIL-53(Al)-NH2, while the extremely low adsorption capacity of MIL-53(Al) for the dyes may be main caused by the "breathing" behavior of MIL-53(Al). The factors including adsorption time, temperature, and the pH of solution that affected adsorption of the two dyes on MIL-53(Al)-NH2, were studied. Pseudo first-order kinetic, pseudo second-order kinetic, and Weber Morris models were used to fit the adsorption data, and the pseudo second-order kinetic model showed a better fit for the adsorption of methylene blue and malachite green than that of the pseudo first-order kinetic model. Furthermore, the internal diffusion model which represented by Weber-Morris model was involved in the step of speed control, but it was not the only speed control step, while out-diffusion also played an important role in the adsorption process. The adsorption isotherm and thermodynamics of methylene blue and malachite green on MIL-53(Al)-NH2 were also studied. The adsorption of methylene blue and malachite green dyes on MIL-53(Al)-NH2 can be fitted to both Langmuir and Freundlich isotherm, but the former was better than the latter. The adsorption thermodynamic experiments demonstrated that adsorption reaction was spontaneous and endothermic. Finally, according to the experimental phenomenon, the possible mechanism of adsorption was proposed. Besides, the used adsorbent can be reused for adsorptive removal through simply washing.