12 Chlorophenols Dechlorination Water Treatment Using …
287
Table 12.1 Percentages of iron oxides present on the iron surface at the start, after 1 day, 12 days,
and end of experiments (estimated by MCR-ALS analysis)
Treatment
Type of CP
Type of iron oxide
Akgt Hemt Magnt Lepidt Goeth Wus Ferrih
ZVI
(as-received) a
–
–
74
–
–
24
<5
ZVI
(acid-washed) b
–
–
100
–
–
–
–
Ni/Fe c
–
–
100
–
–
–
–
Ni/Fe d
PCP
–
<5
95
–
–
<5
–
2,3,4,6-TeCP –
<5
90
–
7
–
–
2,4,6-TCP
–
5
86
5
<5
<5
–
2,4-DCP
<5
–
82
<5
<5
<5
<5
Ni/Fe e
PCP
–
5
88
–
–
7
–
2,3,4,6-TeCP –
<5
84
–
12
–
–
2,4,6-TCP
<5
6
74
7
<5
7
–
2,4-DCP
5
–
75
10
<5
<5
<5
Ni/Fe f
PCP
–
10
71
–
–
13
6
2,3,4,6-TeCP –
<5
75
–
23
–
–
2,4,6-TCP
<5
14
61
8
5
12
–
2,4-DCP
9
–
65
15
<5
<5
6
Akgt Akaganeite, Hemt Haematite, Magnt Magnetite, Lepidt Lepidocrocite, Goeth Goethite,
Wus Wustite, Ferrih Ferrihydrite
a The ZVI (as-received) surface at the start of the experiment
b The ZVI (acid-washed) surface at the start of the experiment
c The Ni/Fe bimetal surface at the start of the experiment
d The Ni/Fe surface after 1 day of reaction
e The Ni/Fe surface after 12 days of reaction
f The Ni/Fe surface after 25 days of reaction
“–” Respective iron oxide(s) were not detected on the metal surface(s)
“<5” Percentage amount of respective iron oxide(s) detected on the metal surface(s) was less than
5%
magnetite has a greater solubility compared to Fe(OH) 2 (Cornell and Schwertmann
2003). Thus, the incorporated CP and/or degradation products with the passive iron
oxides seemed to be difficult to extract using HCl and ethyl acetate leading to poor
CP mass balance (Fig. 12.1).
On the other hand, during the reaction of PCP and 2,3,4,6-TeCP with Ni/Fe
bimetal, magnetite was the dominant oxide phase at the beginning and throughout the reaction period although some passive oxides started accumulating on the
Ni/Fe towards the later part of the 25 days reaction period (Table 12.1). Presence
of low levels of passivating oxides on the Ni/Fe surface during the reaction of PCP
and 2,3,4,6-TeCP could potentially result in (1) lower levels of incorporation of the
degradation products (i.e. CPs with lower degree of chlorination) with such oxide
287
Table 12.1 Percentages of iron oxides present on the iron surface at the start, after 1 day, 12 days,
and end of experiments (estimated by MCR-ALS analysis)
Treatment
Type of CP
Type of iron oxide
Akgt Hemt Magnt Lepidt Goeth Wus Ferrih
ZVI
(as-received) a
–
–
74
–
–
24
<5
ZVI
(acid-washed) b
–
–
100
–
–
–
–
Ni/Fe c
–
–
100
–
–
–
–
Ni/Fe d
PCP
–
<5
95
–
–
<5
–
2,3,4,6-TeCP –
<5
90
–
7
–
–
2,4,6-TCP
–
5
86
5
<5
<5
–
2,4-DCP
<5
–
82
<5
<5
<5
<5
Ni/Fe e
PCP
–
5
88
–
–
7
–
2,3,4,6-TeCP –
<5
84
–
12
–
–
2,4,6-TCP
<5
6
74
7
<5
7
–
2,4-DCP
5
–
75
10
<5
<5
<5
Ni/Fe f
PCP
–
10
71
–
–
13
6
2,3,4,6-TeCP –
<5
75
–
23
–
–
2,4,6-TCP
<5
14
61
8
5
12
–
2,4-DCP
9
–
65
15
<5
<5
6
Akgt Akaganeite, Hemt Haematite, Magnt Magnetite, Lepidt Lepidocrocite, Goeth Goethite,
Wus Wustite, Ferrih Ferrihydrite
a The ZVI (as-received) surface at the start of the experiment
b The ZVI (acid-washed) surface at the start of the experiment
c The Ni/Fe bimetal surface at the start of the experiment
d The Ni/Fe surface after 1 day of reaction
e The Ni/Fe surface after 12 days of reaction
f The Ni/Fe surface after 25 days of reaction
“–” Respective iron oxide(s) were not detected on the metal surface(s)
“<5” Percentage amount of respective iron oxide(s) detected on the metal surface(s) was less than
5%
magnetite has a greater solubility compared to Fe(OH) 2 (Cornell and Schwertmann
2003). Thus, the incorporated CP and/or degradation products with the passive iron
oxides seemed to be difficult to extract using HCl and ethyl acetate leading to poor
CP mass balance (Fig. 12.1).
On the other hand, during the reaction of PCP and 2,3,4,6-TeCP with Ni/Fe
bimetal, magnetite was the dominant oxide phase at the beginning and throughout the reaction period although some passive oxides started accumulating on the
Ni/Fe towards the later part of the 25 days reaction period (Table 12.1). Presence
of low levels of passivating oxides on the Ni/Fe surface during the reaction of PCP
and 2,3,4,6-TeCP could potentially result in (1) lower levels of incorporation of the
degradation products (i.e. CPs with lower degree of chlorination) with such oxide