(9) [10,34]. Fe(II) could be generated by the reduction of Fe(III) by
R (Eq. (10)); further enhancing the generation of HO. Therefore,
we hypothesize that there was generation of R (discussed in Section
3.2.3), which could rapidly convert Fe(III) to Fe(II), leading to
more activation of H2O2 and faster benzene degradation in the second
stage. The above hypothesis is confirmed indirectly by the
increase of Fe(II) concentration and by the rapid decrease of
H2O2 concentration at the beginning of the second stage (Fig. 3).
This is also consistent with the reduced intensity of HO observed
with the increase of CF concentration (Fig. 4). In total, the results
indicated that HO was primarily responsible for benzene
degradation. It should be pointed out that the formation of HO
depend strongly on the generation and intensity of R and O2
radicals.
HO þ R ! ROH k8 ¼ 5:1 7:6 109 M1 s1 ð8Þ
ROH þ O2½$ RðOHÞO
2
! ROH þ HO
2 k9 ¼ 8 105 M1 s1
ð9Þ
or?ring-opened products
ROH þ FeðIIIÞ ! FeðIIÞ þ products k10 ¼ 7 103 M1 s1 ð10Þ