Reductive Dechlorination of Chloroacetamides with NaBH4 Catalyzed by Zero Valent Iron, ZVI, Nanoparticles in ORMOSIL Matrices Prepared via the Sol-Gel Route

Michael Meistelman,Dror Shamir,Yael Albo,Dan Meyerstein,Ariela Burg,Amos Bardea

doi:10.3390/catal10090986

Abstract

The efficient reductive dechlorination, as remediation of dichloroacetamide and monochloroacetamide, toxic and abundant pollutants, using sodium borohydride catalyzed by zero valent iron nanoparticles (ZVI-NPs), entrapped in organically modified hybrid silica matrices prepared via the sol-gel route, ZVI@ORMOSIL, is demonstrated. The results indicate that the extent of the dechlorination reaction depends on the nature of the substrate and on the reaction medium. By varying the amount of catalyst or reductant in the reaction it was possible to obtain conditions for full dechlorination of these pollutants to nontoxic acetamide and acetic acid. A plausible mechanism of the catalytic process is discussed. The present work expands the scope of ZVI-NP catalyzed reduction of polluting compounds, first reports the catalytic parameters of chloroacetamide reduction, and offers additional insight into the heterogeneous catalyst structure of M0@ORMOSIL sol-gel. The ZVI@ORMOSIL catalyst is ferromagnetic and hence can be recycled easily.

Highlights

Halogenated hydrocarbons are known to be toxic pollutants [1]
They are suitable to be used as nano-catalysts. This colloidal suspension was used in the Zero valent iron (ZVI)@organically modified silica (ORMOSIL) catalyst preparation
It might be suspected that the agglomerated particles that are observed in Figure 1 might originate from solvent evaporation that occurred while placing the suspension sample on the grid, the average values of Sauter mean diameter (SMD), 95.5 nm, and volume mean diameter (VMD) of 95.5 nm, measured for 25 nm ZVI commercial powder in 1.0 M ethanolic suspension, show that agglomeration of a similar degree occurs in the suspension

Summary

Introduction

Halogenated hydrocarbons are known to be toxic pollutants [1]. More than half a century ago it was proposed to study each halogenated compound independently of its homologue hydrocarbon series [1]. While there are number of halogenated pollutants that are monitored by the health authorities, e.g., halo-acetic acids, others which appear on the EPA’s Halo-organic compounds can be reduced electro-chemically [3,4], photo-chemically [5], radiolytically [6], and by a variety of reducing agents [7]. These processes often require a catalyst [8].

Methods

Results

Conclusion