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Magnetic Fe3O4@polyaniline nanocomposites with a tunable core–shell structure for ultrafast microwave-energy-driven reduction of Cr(vi)†
Environmental Science: Nano ( IF 7.3 ) Pub Date : 2017-12-21 00:00:00 , DOI: 10.1039/c7en01075c
Changqing Zhu 1, 2, 3, 4, 5 , Fuqiang Liu 1, 2, 3, 4, 5 , Li Song 1, 2, 3, 4, 5 , Hao Jiang 1, 2, 3, 4, 5 , Aimin Li 1, 2, 3, 4, 5
Affiliation  

Magnetic core–shell Fe3O4@polyanilines (Fe3O4@PANI) were controllably synthesized to harvest microwave (MW) energy for ultrafast Cr(VI) reduction. The nanocomposites are excellent MW acceptors due to the combination of the magnetic loss of Fe3O4 and dielectric loss of PANI. Under MW irradiation, abundant hot spots are generated on Fe3O4@PANI to accelerate the reduction of surface-bound Cr(VI). Moreover, Fe3O4@PANI is highly stable in an acidic solution and readily recoverable with an external magnet after use. The PANI shell possesses good enrichment ability for Cr(VI), creating a high Cr(VI) surface concentration which benefits the sequential reduction. Furthermore, an increase in the PANI coating amount from 24.78% to 55.15% increases the Cr(VI) adsorption capacity (qe) from 0.63 mmol g−1 to 1.68 mmol g−1, which linearly enhances the removal rate constant (k) of Cr(VI) under an MW field as k = 0.30qe − 0.03. The addition of oxalic acid as a sacrificial electron donor increases the Cr(VI) removal rate by 120.09% and protects the PANI shell from excessive oxidation by Cr(VI); this prolongs the lifetime of Fe3O4@PANI. In the presence of oxalic acid, the MW-driven Cr(VI) reduction on Fe3O4@PANI proceeds at a rate constant of 0.5773 min−1, which is much higher than that of palladium-based chemocatalysis. Moreover, Fe3O4@PANI can be in situ regenerated by MW and directly reused in the next cycle, and no efficiency loss occurs in 5 continuous runs. The mechanism study based on Cr species tracking and solid analyses indicates that a synergistic adsorption and reduction cycle proceed consecutively, contributing to the rapid Cr(VI) removal. This study demonstrates that Fe3O4@PANI is a promising alternative to utilize MW for ultrafast Cr(VI) reduction and has the advantages of time-saving and energy efficiency.

中文翻译:

具有可调核-壳结构的 磁性Fe 3 O 4 @聚苯胺纳米复合材料,用于超快微波能量驱动的Cr(vi)还原

磁性核-壳Fe 3 O 4 @聚苯胺(Fe 3 O 4 @PANI)是可控制合成的,以收集微波(MW)能量以超快地还原Cr(VI)。由于Fe 3 O 4的磁损耗和PANI的介电损耗的组合,纳米复合材料是出色的MW受体。在微波辐射下,Fe 3 O 4 @PANI上产生大量热点,以加速表面结合Cr(VI)的还原。此外,Fe 3 O 4@PANI在酸性溶液中高度稳定,使用后易于用外部磁体回收。PANI壳对Cr(VI)具有良好的富集能力,可产生较高的Cr(VI)表面浓度,这有利于顺序还原。此外,PANI涂层量从24.78%增加到55.15%,可以使Cr(VI)吸附容量(q e)从0.63 mmol g -1增加到1.68 mmol g -1,从而线性提高去除速率常数(k)。k = 0.30 q e时的MW场下Cr(VI)的分布− 0.03。草酸作为牺牲电子给体的添加使Cr(VI)的去除率提高了120.09%,并保护了PANI壳免受Cr(VI)过度氧化的影响;这延长了Fe 3 O 4 @PANI的寿命。在草酸的存在下,Fe 3 O 4 @PANI上的MW驱动的Cr(VI)还原以0.5773 min -1的速率常数进行,这远高于钯基化学催化的速率常数。此外,Fe 3 O 4 @PANI可以原位存在由MW再生并在下一个循环中直接重复使用,并且连续5次运行均未发生效率损失。基于Cr物种跟踪和固相分析的机理研究表明,协同的吸附和还原循环连续进行,有助于快速去除Cr(VI)。这项研究表明,Fe 3 O 4 @PANI是一种利用兆瓦超快还原Cr(VI)的有前途的替代方法,并且具有省时和节能的优势。
更新日期:2017-12-21
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