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Oxidative Degradation And Kinetics Of Chlorinated Ethylenes By Potassium Permanganate

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The oxidative treatment of chlorinated ethylenes in ground water using permanganate was

investigated in a series of batch kinetic tests. Five chlorinated ethylenes including tetrachloroethy-

lene PCE., trichloroethylene TCE., and three isomers of dichloroethylenes DCEs. were

examined. The degradation process was rapid with pseudo-first-order rate constants ranging from

4.5=10y5 to 0.03 sy1 at MnO4ys1 mM. The rate increased with a decreasing number of

chlorine substituents on the ethylene. The higher reactivity of trans-DCE kobss30=10y3 sy1

at MnOys1 mM. as compared to cis-DCE k s0.9=10y3 sy1 at MnOys1 mM. is thought 4 obs 4

to be caused by a significant steric effect due to the formation of a large cyclic activated complex.

TCE oxidation as a second-order reaction was confirmed and the rate constant, ks0.67"0.03

My1 sy1, is independent of pH over the range of 4–8. The activity of both Cly and hydrogen

ions was monitored over time and suggests essentially complete dechlorination, making the

degradation products less harmful than the parent compounds. Competition for MnO4y from other

organic compounds in ground water or highly contaminated ground water was also evaluated in

experiments. A simple and quick approach was demonstrated to estimate permanganate consumption

by other organic compounds for field applications and to predict the TCE degradation rate in

a system involving multiple contaminants. The modeling results suggest that the effect of

autocatalysis by MnO2 on TCE degradation is significant when the system contains high

concentration levels of MnO4y and TOC. q1999 Elsevier Science B.V. All rights reserved.

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