A mechanically synthesized SiO2–Fe metal matrix composite for effective dechlorination of aqueous 2-chlorophenol: the optimum of the preparation conditions

Abstract

In this study, abrasives-reinforced metal matrix composites (MMCs) with a microscale size synthesized by ball milling (BM) could achieve highly active and stable dechlorination efficiency for aqueous 2-chlorophenol (2-CP). The preparation process of this composite via BM was optimized to obtain a high degradation efficiency, especially for the effect of the abrasives including B₄C, SiC, α-Al₂O₃, SiO₂, Fe₃O₄ and Na₂SO₄. The results showed that the hardness of the abrasives in the Fe-based MMCs was closely related with their dechlorination performance. Subsequently, the optimal abrasive, i.e. SiO₂ was further investigated for its proper milling conditions with zero-valent iron (ZVI) particles including optimal SiO₂ size, SiO₂ loading, milling time, and the dosage of the process control agent (PCA). Additionally, the influence of other metal categories including Al and Si was also investigated for dechlorination; and their low reaction efficiencies were closely related with their passivating film. Finally, the longevity test suggested that the decreased reactivity of the SiO₂–Fe MMC during the storage in air could be recovered when consecutively used, mainly due to the promoting effects of the inherent structure of SiO₂–Fe MMC with the Fe/C and Fe/SiO₂ interfaces, as well as the effective regeneration of the reactive sites by continuous iron dissolution.