nZVI@mesoSiO2的可控合成及应用性能研究

采用改进的两步法在原位基础上合成了以纳米零价铁(nano Zero Valent Iron,nZVI)为核芯的核壳型介孔二氧化硅(nZVI@mesoSiO_2).同时,通过简单地调控铁源用量得到具有单一nZVI核芯和不同壳层厚度的核壳型纳米复合材料.结果发现,铁源用量的增加会导致核芯尺寸减小、壳层厚度增加及颗粒比表面积下降.当铁源用量为2.78 g时,得到的nZVI@mesoSiO_2不仅具有较高的比表面积和单一且均匀的孔径分布,而且对2,4,6-三氯苯酚(2,4,6-Trichlorophenol, 2,4,6-TCP)的去除表现出很高的性能.影响因素实验表明,材料的最佳投加量为1.0 g·L~(-1),体系适宜初始pH为5.0,污染物初始浓度升高会导致去除效果下降,并且反应体系内乙二胺四乙酸(EDTA)的存在可以提高2,4,6-TCP的去除率.材料的重复利用实验结果表明,经过多次循环反应后会导致材料nZVI核芯的失活和孔道的堵塞.本研究不仅为制备可控壳层厚度的核壳型介孔材料提供了理论指导,而且为进一步改性合成对2,4,6-TP具有高选择性的复合材料提供了依据.

Controllable synthesis and application performance of nZVI@mesoSiO2

In this study, the core/shell mesoporous silica (nZVI@mesoSiO₂) with nano zero valent iron (nZVI) core was fabricated based on an improved two-step method. A series of composite materials with diverse nZVI core and shell thickness could be obtained through simple regulating the dosage of the iron sources. As a result, as the increasing dosage of iron decreased the core dimension of the nZVI, while thickened the silica coating and, increased the specific surface area. When the dosage of the iron was 2.78 g, the product particle not only depicted a high specific surface area and a narrow pore-size distribution but also showed high performance for the removal of 2,4,6-TCP. Experimental study of factor influencing indicated that the optimum conditions were the nZVI@mesoSiO₂ dosage of 1.0 g·L^-1and initial solution pH of 5.0. The increased initial concentration of the contaminants could lead to a decrease in removal efficiency. And the presence of EDTA had a positive effect on the 2,4,6-TCP removal. Furthermore, the repeated experiment proved that the circular reaction may cause the inactivation of the nZVI core and the blockage of the pore structure. This experiment provides not only a theoretical guidance for the preparation of core/shell mesoporous materials with controllable shell thickness but also a basis for the synthesis and further modification of the composites with high selectivity for 2,4,6-TCP.