The kinetics of oxidation of perchloroethylene (PCE), trichloroethylene (TC
E), three isomers of dichloroethylene (DCE) and vinyl chloride (VC) by pota
ssium permanganate (KMnO4) Were studied in phosphate-buffered solutions of
pH 7 and ionic strength similar to0.05 M and under isothermal, completely m
ixed and zero headspace conditions. Experimental results have shown that th
e reaction appears to be second order overall and first order individually
with respect to both KMnO4 and all chlorinated ethenes (CEs), except VC. Th
e degradation of VC by KMnO4 is a two-consecutive-step process. The second
step, being the rate-limiting step, is of first order in VC and has an acti
vation energy (E-a) of 7.9 +/-1 kcal mol(-1). The second order rate constan
ts at 20 degreesC are 0.035 +/-0.004 M-1 s(-1) (PCE), 0.80 +/-0.12 M-1 s(-1
) (TCE), 1.52 +/-0.05 M-1 s(-1) (cis-DCE), 2.1 +/-0.2 M-1 s(-1) (1,1-DCE) a
nd 48.6 +/-0.9 M-1 s(-1) (trans-DCE). The E-a and entropy (DeltaS*) of the
reaction between KMnO4 and CEs (except VC) are in the range of 5.8-9.3 kcal
mol(-1) and -33 to -36 kcal mol(-1) K-1, respectively. Moreover, KMnO4 is
able to completely dechlorinate CEs, and the increase in acidity of the sol
ution due to CE oxidation by KMnO4 is directly proportional to the number o
f chlorine atoms in CEs. (C) 2001 Elsevier Science B.V. All rights reserved
.