Cr(VI) reduction by bio and bioinorganic catalysis via use of bio‐H₂: a sustainable approach for remediation of wastes

Abstract

Use of biologically-produced hydrogen (bio-H 2 ) as an electron donor for Cr(VI) reduction by native and palladized cells of Desulfovibrio vulgaris NCIMB 8303 was demonstrated. The bio-H 2 was produced fermentatively by Escherichia coli HD701 (a strain upregulated with respect to formate hydrogenlyase expression) using glucose solution or two industrial confectionery wastes as fermentable substrates. Maximum Cr(VI) reduction occurred at the expense of bio-H 2 using palladized biomass (bio-Pd(0)), with negligible residual Cr(VI) remaining from a 0.5 mmol dm −3 solution after 2.5 h. Use of bio-H 2 as the electron donor for Cr(VI) reduction by agar-immobilized bio-Pd(0) in a continuous-flow system gave 90% reduction efficiency at a flow residence time of 0.7 h, which was maintained for the duration of bio-H 2 evolution by E. coli HD701. This study shows the potential to remediate toxic metal waste at the expense of food processing waste, as a sustainable alternative to landfilling.

Bio‐palladium: from metal recovery to catalytic applications

“…Yet, the external supply of H 2 gas can give rise to large costs and technical difficulties because of the high safety risks for gas storage ( Hennebel et al ., 2011b ). As discussed in Reactor set‐ups using a bio‐Pd catalyst: state of the art , several reactor types were constructed to limit the hydrogen supply, for example by a membrane contactor ( Hennebel et al ., 2010 ), or to produce hydrogen gas in a sustainable way, for example by using microbially produced H 2 ( Humphries et al ., 2007 ), or by using a H 2 ‐producing species for Pd reduction, e.g. C. pasteurianum ( Chidambaram et al ., 2010 ).…”

Effective treatment of alkaline Cr(VI) contaminated leachate using a novel Pd-bionanocatalyst: Impact of electron donor and aqueous geochemistry

“…Although molecular hydrogen (H 2 ) has been the most extensively used electron donor during Pd(0)-mediated catalysis, it is poorly soluble in water and other more soluble forms of electron donor, typically simple organic acids such as formate (HCOO − ), have been employed as an alternative [5] . This catalytic approach to contaminant remediation has been demonstrated to be effective towards a variety of key contaminants, including chlorinated hydrocarbons [6–10] , nitrobenzene [11] , nitrate [12,13] and Cr(VI) [14–19] .…”