Investigation of factors affecting the physicochemical properties and degradation performance of nZVI@mesoSiO2 nanocomposites

The nZVI@mesoSiO2 nanocomposites with ordered mesoporous structure were successfully prepared through a novel two-step method. Influences of the different conditions on the physicochemical properties and catalytic behavior were investigated. Degradation of 2,4,6-trichlorophenol (2,4,6-TCP) under different conditions was evaluated, and the possible activation mechanism was speculated. The results indicate that only the definite increase in the molar ratio of CTAB/NaOH (cetyltrimethylammonium bromide/sodium hydroxide) helps to obtain the higher specific surface area and narrower pore size distribution of the nZVI@mesoSiO2. The thickness of this silica coating could be easily regulated by changing the dosage of the TEOS (tetraethylorthosilicate) precursor. High dosage of the TEOS (larger than 5 mL) leads to the formation of core-free silica particles and low catalytic activity, while nZVI@mesoSiO2 cannot fully develop at a low dosage (2.5 mL). By controlling different extraction conditions, the nanoscale zero-valent iron core (nZVI) in the composite can be well preserved and corrosion resistant in the whole synthesis process. In this case, the as-prepared nanocomposites offer a high surface area of 638.78 m2 g−1 as well as a large accessible pore volume of 0.49 cm3 g−1 for the degradation, which contributing to a fast and efficient degradation of 2,4,6-TCP from aqueous solutions at an appropriate pH (pH 5.0). Moreover, the reusability investigation indicated that the nZVI cores will be inactivated and the pore will be blocked after repeated cyclic reactions. This comprehensive information provides not only a great understanding of the regulation mechanism of core–shell mesoporous nanocomposites, but also a further useful modification of the composites with high selectivity for 2,4,6-TCP.