Reduction of hexavalent chromium mediated by micro- and nano-sized mixed metallic particles.
A variety of micron-scale mixed metallic particles (Pd/Fe, Ag/Fe, Cu/Fe, Zn/Fe, Co/Fe, Mg/Fe, Ni/Fe, Al/Fe, Si/Fe, Pd/Cu and Pd/Zn; and Pd/Cu/Fe, Pd/Zn/Fe and Zn/Cu/Fe) and selected nano-sized bimetallic analogs (Pd/Fe, Cu/Fe and Pd/Cu) were evaluated for reducting activity with Cr(VI) in a surfactant preparation (Tween 20) under a variety of reaction conditions. Relative to the reactivity of the zero-valent iron, the tested bimetallic mixtures (Pd/Fe>Pd/Zn>Ag/Fe>Ni/Fe>Zn/Fe>Pd/Cu>Cu/Fe) appreciably increased the pseudo-first-order rate constant. The Zn/Cu/Fe represented a cost-effective preparation providing comparable or improved kinetic parameters relative to the more expensive palladized bimetallic mixtures. The Pd/Fe, Cu/Fe and Pd/Cu nano-sized particles proved to be more reactive (up to 100-fold) for the reductive remediation of Cr(VI). The results were comparable when working with nano-sized Cu and Fe particles, suggesting that the cementation of a noble metal serves not only as a reaction catalyst but also provides protection to the metallic surface, impeding its rapid inactivation.
Rivero-Huguet
Mario
M
Department of Food Science and Agricultural Chemistry, McGill University, Ste-Anne-de-Bellevue, Qc, Canada.
Marshall
William D
WD
D002857:Chromium / Q000737:chemistry*; D003365:Costs and Cost Analysis; D052918:Environmental Restoration and Remediation / Q000191:economics / Q000379:methods*; D007700:Kinetics; D019216:Metals, Heavy / Q000737:chemistry; D010316:Particle Size; D011136:Polysorbates; D019163:Reducing Agents
D019216:Metals, Heavy; D011136:Polysorbates; D019163:Reducing Agents; D002857:Chromium; C074702:chromium hexavalent ion