Enhanced Removal of Hexavalent Chromium in the Presence of H2O2 in Frozen Aqueous Solutions
- Enhanced Removal of Hexavalent Chromium in the Presence of H2O2 in Frozen Aqueous Solutions
- Kim, Kitae
Bokare, Alok D.
Yoon, Ho Il
- Issue Date
- Kim, Kitae., et al. 2015. Enhanced Removal of Hexavalent Chromium in the Presence of H2O2
- The reductive transformation of Cr(VI) to Cr(III) by H2O22O2 concentration (20-1000 μM), pH (3-11), and freezing temperature (-10 to -30 °C). The observed molar ratio of consumed [H2O2] to reduced [Cr(VI)] in ice was in close agreement with the theoretical (stoichiometric) molar ratio (1.5) for H2O2 -mediated Cr(VI) reduction through proton-coupled electron transfer (PCET). The synergistic increase in Cr(VI) reduction in water by increasing the H2O2
and proton concentrations confirms that the freeze concentration of both H2O2 and protons in the liquid brine is primarily responsible for the enhanced Cr(VI) reduction in ice. In comparison, the one-electron
reduction of Cr(VI) to Cr(V) and subsequent reoxidation of Cr(V) to Cr(VI) is the major reaction mechanism in aqueous solution. The reduction efficiency of Cr(VI) by H2O2 in the frozen aqueous electroplating wastewater was similar to that in the frozen aqueous deionized water, which verifies the enhanced reduction of Cr(VI) by freezing in real Cr(VI)-contaminated aquatic systems.
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