Zero-valent iron nanoparticles entrapped in SiO₂ sol-gel matrices: A catalyst for the reduction of several pollutants

Zero-valent iron-nanoparticles (ZVI-NPs) entrapped in silica matrices through a sol-gel procedure are investigated as redox catalysts with BH₄⁻ (NaBH₄) as the reducing agent. The results indicated that the matrix functions as an efficient and multifunctional catalyst for the reduction of halo-acetic acids (HAAs), [BrO₃⁻] and 4-nitrophenol pollutants present in the contaminated water. The present study revealed that the reduction mechanism depends on the nature of the substrate, M⁰ used and the rate of the reductant addition (batch mode reactor system). The novelty of the present work is double-fold: First, in pointing out that the mechanism of the catalytic de-halogenation reaction depends on the nature of M⁰-NPs used as a catalyst, probably due to the different over-potential for the HER reaction on each M⁰-NPs and second, the development of a cost-effective remediation alternative compared to the analogous Au⁰-NPs or Ag⁰-NPs catalysts reported in the literature.