(359b) Reductive Degradation of Co-Contaminant Medium of TCE and Cr(VI) Using Atomized Iron Powder
AIChE Annual Meeting
2017
2017 Annual Meeting
Environmental Division
Fundamentals and Applications for Hazardous Waste Treatment
Tuesday, October 31, 2017 - 12:55pm to 1:20pm
Elemental Iron in the form of atomized iron powder (Zero Valent Iron, ZVI or Fe(0)) was used to individually and simultaneously degrade a co-contaminant medium of hexavalent chromium (Cr(VI)) and trichloroethylene (TCE). Under appropriate conditions of initial concentrations, the overall degradation reaction was modeled as a combination of two pseudo-first order reactions. The reaction kinetics, degradation efficiency and reductant demand of both Cr(VI) and TCE were determined. Over a 2-hour period, degradation of TCE and Cr(VI) yielded 85% and 25% reduction, respectively with excess amounts of Fe(0). Over a 5-hour period, TCE percent remained at 85% whilst Cr(VI) degradation increased rapidly to almost 100%. This observation is attributed to: (1) increased polarization and destabilization of the double bond in the TCE leading to cleavage of the Chloride and solubility equilibria; (2) the formation of a passive layer of chromic-ferric mixed oxides and oxyhydroxides on the surface of iron particles, which impeded degradation but dissolved due to increasing acidity to expose fresh reactive sites. The observed pseudo-first order degradation rate constants for individual and combined degradations of the co-contaminant were determined.