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

DOI: 10.1016/j.apcatb.2015.01.017 DOI Help
PMID: 26146457 PMID Help

Authors: Mathew Watts (University of Manchester) , Victoria Coker (University of Manchester) , Stephen Parry (Diamond Light Source) , Russell A. P. Thomas (Diamond Light Source) , Robert Kalin (Department of Civil and Environmental Engineering, University of Strathclyde) , Jonathan R. Lloyd (Department of Civil and Environmental Engineering, University of Strathclyde)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Applied Catalysis B: Environmental , VOL 170-171 , PAGES 162 - 172

State: Published (Approved)
Published: July 2015
Diamond Proposal Number(s): 8163

Open Access Open Access

Abstract: Palladium catalysts offer the potential for the effective treatment of a variety of priority reducible pollutants in natural waters. In this study, microbially synthesized magnetite nanoparticles were functionalized with Pd(0), creating a highly reactive, magnetically recoverable, nano-scale catalyst (Pd-BnM). This was then investigated for the treatment of model Cr(VI) contaminated solutions at a range of pH values, and also alkaline Cr(VI) contaminated leachates from chromite ore processing residue (COPR); a contaminant issue of global concern. The sample of COPR used in this study was obtained from a site in Glasgow, UK, where extensive Cr(VI) contamination has been reported. In initial experiments Pd-BnM was supplied with H2 gas or formate as electron donors, and Cr(VI) removal from model synthetic solutions was quantified at various pH values (2–12). Effective removal was noted at neutral to environmentally relevant alkaline (pH 12) pH values, while the use of formate as an electron donor resulted in loss of performance under acidic conditions (pH 2). Reaction kinetics were then assessed with increasing Pd-BnM loading in both model pH 12 Cr(VI) solutions and the COPR leachate. When formate was used as the electron donor for Pd-BnM, to treat COPR leachate, there was significant inhibition of Cr(VI) removal. In contrast, a promotion of reaction rate, was observed when H2 was employed. Upon sustained reaction with model Cr(VI) solutions, in the presence of excess electron donor (formate or H2), appreciable quantities of Cr(VI) were removed before eventual inactivation of the catalyst. Faster onset of inactivation was reported in the COPR leachates, removing 4% and 64% of Cr(VI) observed from model Cr(VI) solutions, when formate and H2 were used as electron donors, respectively. XAS, TEM-EDX and XPS analysis of the catalysts that had been inactivated in the model solution, showed that the surface had an extensive covering of reduced Cr(III), most likely as a CrOOH phase. COPR reacted catalysts recorded a lower abundance of Cr(III) alongside a high abundance of the leachate components Ca and Si, implicating these elements in the faster onset of inactivation.

Journal Keywords: Cr(Vi); Magnetite; Remediation; Alkaline; Inactivation

Subject Areas: Chemistry

Instruments: B18-Core EXAFS

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