Ag(0) and Au(0) Nanoparticles Encapsulated in Sol-Gel Matrices as Catalysts in Reductive De-halogenation Reactions

Yael Albo, Chemical Engineering Department, Ariel University, Ariel, Israel
Michael Meistelman, Chemical Engineering Department, Ariel University, Ariel, Israel
Jaydeep Adhikary, Chemical Sciences Department, Ariel University, Ariel, Israel
Ariela Burg, Chemical Engineering Department , Sami Shamoon College Of Engineering, Beer Sheva, Israel
Dror Shamir, Chemistry Department, Nuclear Research Centre Negev, Beer Sheva, Israel
Dan Meyerstein, Chemical Sciences Department, Ariel University, Ariel, Israel


The sol – gel technology can be efficiently utilized in heterogeneous catalysis. The incorporation of a homogeneous catalyst into the matrix combines the specificity and reproducibility of the homogeneous catalyst with the advantages of heterogeneous catalysts (stabilization and easy separation and recycling of the catalyst). The chemical behavior of these catalysts is affected by: the flexibility of the sol-gel cages and the accessibility of the entrapped species. These properties can be controlled and tailored due to the large number of adjustable parameters of the sol-gel synthesis e.g. the nature and concentration of the precursors, water concentration used, temperature, solvent, catalyst used to accelerate the synthesis of the matrix, aging and drying conditions.
Halogenated pollutants have low solubility, are toxic, tend to accumulate in food chains and are the most often found contaminates in subsurface environment. Various approaches for their degradation have been studied including bioremediation, chemical methods based on zero valent iron and bimetallic particles and electro-catalysis. In this study Ag0 and Au0 nanoparticles incorporated in SiO2 matrices via the sol-gel synthesis route have been successfully applied as heterogeneous catalysts for the reductive dehalogenation of halogenated organic compounds by NaBH4. Matrices with different compositions were prepared in order to optimize the preparation procedure. The reduction percentage and the product distribution are affected by the matrix composition and the reduction conditions; pH, substrate concentration and NaBH4 rate of addition.