Key role of pore size in Cr(VI) removal by the composites of 3-dimentional mesoporous silica nanospheres wrapped with polyaniline
Key role of pore size in Cr(VI) removal by the composites of 3-dimentional mesoporous silica nanospheres wrapped with polyaniline
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DOI：
10.1016/j.scitotenv.2020.139009
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发表时间：
2020-08-10
影响因子：
9.8
通讯作者：
Liu, Xiang
中科院分区：
文献类型：
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作者：
Li, Jiacheng;Li, Miao;Liu, Xiang
在油水双相体系中合成了一系列具有不同孔径的三维二氧化硅纳米球，并通过控制油相组成来调节其孔径。然后用聚苯胺包裹二氧化硅纳米球，对其进行表征，并将得到的二氧化硅纳米球-聚苯胺复合材料用于去除Cr（VI）。聚苯胺是由苯胺聚合而成的。介孔二氧化硅具有足够的枝状孔道，为苯胺的聚合提供了较大的接触面。此外，介孔二氧化硅纳米球有利于聚苯胺的分散和水中Cr（VI）的转移。孔径最大（约15.4 nm）的二氧化硅纳米球-聚苯胺复合材料对Cr（VI）的去除效果最好。对其动力学特性进行了研究，结果符合拟二阶动力学模型。此外，与其他阴离子（H2PO4-， SO42-等）相比，复合材料保持了较高的Cr（VI）去除效率，表明其在实际废水处理中具有良好的前景。在紫外照射下，二氧化硅-聚苯胺复合材料对Cr （VI）的去除率显著提高。根据紫外-可见光电子能谱和x射线光电子能谱的研究结果，讨论了电子和H+对Cr（VI）还原的影响（pH值对吸附量的影响）。机理研究表明，Cr（VI）的去除分为吸附和还原两个阶段。带负电的Cr（VI）首先通过静电吸引与带正电的质子化胺基相互作用，然后通过聚苯胺上的胺基提供的电子和H+进一步还原为毒性较小的Cr（III）。(c) 2020 Elsevier B.V.版权所有
A series of three-dimensional silica nanospheres with different pore sizes was synthesized in a biphasic oil-water system and their pore dimensions were adjusted by controlling the composition of the oil phase. The silica nanospheres were then wrapped with polyaniline, characterized, and the obtained silica nanosphere-polyaniline composites were used for the removal of Cr(VI). Polyaniline was generated by the polymerization of aniline. The mesoporous silica has sufficient dendritic pore channels and offers a large contact surface for the polymerization of aniline. Furthermore, the mesoporous silica nanospheres are beneficial for dispersing polyaniline and transferring aqueous Cr(VI). The silica nanosphere-polyaniline composite with the largest pore size (similar to 15.4 nm) showed the best Cr(VI) removal performance. We also investigated the kinetic characteristics and the result could be fitted to the pseudo-second-order kinetic model. Moreover, we demonstrate that the composites maintain a high Cr(VI) removal efficiency compared to other anions (H2PO4-, SO42-, etc.), indicating their good prospect in practical wastewater treatment. Remarkably, the silica-polyaniline composites showed enhanced Cr (VI) removal efficiency under UV-irradiation. The effects of electrons and H+ on Cr(VI) reduction are also discussed based on the results of UV-vis and X-ray photoelectron spectroscopic studies and bath experiments (influence of pH on adsorption capacity). Mechanistic studies indicate that the Cr(VI) removal occurs in two stages-adsorption and reduction. The negatively charged aqueous Cr(VI) species first interact with the positively charged protonated amine groups via electrostatic attraction, and are then further reduced to less-toxic Cr(III) by the electrons and H+ donated by the amine groups on polyaniline. (c) 2020 Elsevier B.V. All rights reserved.