Chen Bo, Yue Wenli, Zhao Huinan, Long Fengxia, Cao Yangrui, Pan Xuejun
Faculty of Environmental Science and Engineering, Kunming University of Science and Technology Kunming 650500 P. R. China
RSC Adv. 2019 Feb 6;9(9):4722-4734. doi: 10.1039/c8ra08760a. eCollection 2019 Feb 5.
Most recently, the continuous deterioration of the aquatic environment triggered by both heavy metals and synthetic organic dyes has imparted serious threats to the ecosphere and drinking water safety. However, it is still extremely challenging to treat complex wastewater containing these two classes of pollutants a one-step method owing to the significant differences in their physicochemical properties. In the current work, versatile magnetic MWCNTs decorated with PEI (denoted as MWCNTs@FeO/PEI) was fabricated by a facile, rapid and reproducible strategy and applied to as a robust adsorbent for simultaneously removing methyl orange (MO) and Cr(vi) from aqueous solutions. The physicochemical properties of the as-designed nanohybrid were investigated using various analytical techniques, XRD, FT-IR, SEM, TEM, VSM, zeta potential, It was found that the surface charge properties of the MWCNTs as well as its dispersion in aqueous solution were greatly changed after the introduction of PEI molecules. The resulting nanohybrid exhibited attractive adsorption capabilities toward anionic MO and Cr(vi). In the perspective of a mono-pollutant system, the time-dependent adsorption process matched well with a pseudo-second-order kinetics equation, the adsorption isotherm data at r.t. were well fitted by a Langmuir model with maximum monolayer uptake capacity of 1727.6 mg g for MO and 98.8 mg g for Cr(vi), and the removal process of both pollutants was thermodynamically spontaneous and exothermic. In the MO-Cr(vi) binary system, the uptake of Cr(vi) by the as-prepared adsorbent was evidently enhanced by the presence of MO, while the coexisting Cr(vi) exerted a small negative effect on the sorption of MO; which was attributed to the different adsorption mechanisms of both pollutants on the as-recommend adsorbent. The much better adsorbing performance of the resulting MWCNTs@FeO/PEI for MO and Cr(vi) than that of the pristine MWCNTs or the MWCNTs/FeO composite was mainly ascribed to the high surface area of the MWCNTs, the high density of protonated N-rich groups of PEI as well as the excellent dispersion and solubility of the resulting nanocomposites. Moreover, the obtained nanohybrids can be easily recovered after being used by a permanent magnet and still retained high stability and excellent reusability after consecutive adsorption-desorption cycles, implying its great potential in practical applications. Therefore, the as-fabricated MWCNTs@FeO/PEI composite could be recommended as a promising candidate adsorbent for the simultaneous capture of MO and Cr(vi) from complex wastewater multiple uptake mechanisms ( electrostatic attraction, π-π stacking and hydrogen bonding).
最近，由重金属和合成有机染料引发的水生环境持续恶化，对生态系统和饮用水安全构成了严重威胁。然而，由于这两类污染物的物理化学性质存在显著差异，采用一步法处理含有这两类污染物的复杂废水仍然极具挑战性。在当前工作中，通过一种简便、快速且可重复的策略制备了用聚乙烯亚胺修饰的多功能磁性多壁碳纳米管（记为MWCNTs@FeO/PEI），并将其用作一种强大的吸附剂，用于同时从水溶液中去除甲基橙（MO）和Cr(Ⅵ)。使用各种分析技术对所设计的纳米杂化物的物理化学性质进行了研究，如XRD、FT-IR、SEM、TEM、VSM、zeta电位等。结果发现，引入聚乙烯亚胺分子后，多壁碳纳米管的表面电荷性质及其在水溶液中的分散性发生了很大变化。所得纳米杂化物对阴离子型MO和Cr(Ⅵ)表现出有吸引力的吸附能力。从单污染物体系来看，时间依赖性吸附过程与伪二级动力学方程拟合良好，室温下的吸附等温线数据用Langmuir模型拟合良好，MO的最大单层吸附容量为1727.6 mg/g，Cr(Ⅵ)为98.8 mg/g，两种污染物的去除过程在热力学上是自发的且放热。在MO-Cr(Ⅵ)二元体系中，所制备的吸附剂对Cr(Ⅵ)的吸附明显因MO的存在而增强，而共存的Cr(Ⅵ)对MO的吸附有较小的负面影响；这归因于两种污染物在推荐吸附剂上的不同吸附机制。所得MWCNTs@FeO/PEI对MO和Cr(Ⅵ)的吸附性能比原始多壁碳纳米管或MWCNTs/FeO复合材料好得多，主要归因于多壁碳纳米管的高比表面积、聚乙烯亚胺质子化富氮基团的高密度以及所得纳米复合材料优异的分散性和溶解性。此外，所获得的纳米杂化物在使用后可以通过永磁体轻松回收，并且在连续吸附-解吸循环后仍保持高稳定性和优异的可重复使用性，这意味着其在实际应用中具有巨大潜力。因此，所制备的MWCNTs@FeO/PEI复合材料可被推荐为一种有前途的候选吸附剂，用于通过多种吸附机制（静电吸引、π-π堆积和氢键）从复杂废水中同时捕获MO和Cr(Ⅵ)。
