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

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.

“Doing More with Less”: Ni(II)@ORMOSIL, a Novel Sol-Gel Pre-Catalyst for the Reduction of Nitrobenzene

“…1. ZVI@ORMOSIL Characterization ZVI@ORMOSIL characterization was described previously [13]; synthetic procedures were not changed. Interconnected bottleneck constrictions were attributed to the mesoporous structure, possibly contributing to the diffusion-controlled reduction reaction rates.…”

“…Surface morphology of 1% Ni(II)ORMOSIL was examined by STEM/EDAX analysis, and the elemental composition was probed at three different regions of the catalyst (Figure 2). The drying stage of this amorphous silica monolith produces its final morphology through densification and a non-uniform matrix shrinkage [13]. The recorded elemental spectra reveal little Ni presence at the surface, Figure 3.…”

“…Different amounts of detected nickel traces with high variability (spectrum 7, spectrum 8, and 9) strengthen the need for a more surface-sensitive approach. The EDAX and XPS elemental composition detection The drying stage of this amorphous silica monolith produces its final morphology through densification and a non-uniform matrix shrinkage [13]. The recorded elemental spectra reveal little Ni presence at the surface, Figure 3.…”

“…However, Zero Valent Iron (ZVI) is easily aggregated [10] and forms a passivation layer of oxide/hydroxides [10,11]; this limits its application. Recently it was shown that ZVI nanoparticles encapsulated in organically modified silica (ORMOSIL) matrices prepared via the sol-gel synthesis route are proficient catalysts in the reduction of halo-acetic acids, nitrophenol [12] and chloroacetamides pollutants with NaBH 4 [13]. ZVI with NaBH 4 (SBH) efficiently reduces nitrophenol to aminophenol [14].…”

Greener Catalysis for Environmental Applications

“…The catalyst's reusability was also presented in work focused on the reductive removal of pollutants [5]. Therein the authors have utilized elemental iron as a catalyst for the reduction of chloroacetamides.…”