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Chemistry Letters Vol.36, No.5 (2007)
Oxidative Degradation of Organic Pollutants by Hydrogen Peroxide
in the Presence of FePz(dtnCl2)4 under Visible Irradiation
Jie Sun,1;2 Yuping Sun,1 Kejian Deng,ꢀ1 Haobo Hou,2 and Duoyuan Wang1
1The Key Laboratory for Catalysis and Material Science in Hubei,
South-Central University for Nationalities, Wuhan 430073, P. R. China
2College of Resource and Environment, Wuhan University, Wuhan 430072, P. R. China
(Received January 29, 2007; CL-070105; E-mail: dengkj@scuec.edu.cn)
A novel photocatalyst of iron(II)–tetra(5,6-dichloro-1,4-
80 ꢂC and immediately analyzed by GC-MS (Agilent, 6890GC-
5973MS, HP-5 MS column) to determine the degraded compo-
nents. Total organic carbon (TOC) change was detected by a
Jena Muti2100 TOC analyzer.
dithin)porphyrazine (abbreviated as FePz(dtnCl2)4) has been
found to exhibit high catalytic activity to activate hydrogen
peroxide for oxidative degradation of organic pollutants under
visible light irradiation (ꢀ > 420 nm) and wide pH range, in
which Rhodamine B(RhB) and 4-nitro benzoic acid (NBA) were
efficiently degraded and mineralized, while degraded residues
and active oxygen species were also identified.
The photodegradation of RhB (10 mM) at pH 2 solution in
the presence of aqueous FePz(dtnCl2)4 and H2O2 with visible
light illumination was shown in Figure 1, in which the
maximum absorption peak of RhB in 554 nm rapidly decreased
without any wavelength shift and the absorption band at wave-
lengths less than 400 nm gradually increased. This result indicat-
ed that the aromatic chromophore of RhB has been firstly
cleaved to form smaller fragments, reaching 99% conversion
of RhB within 80 min. The smaller fragments were further
analyzed by GCMS, and up to 5 compounds were detected as
possible degradation intermediates (Table 1). All of them were
unequivocally identified using the NIST02.L library database
with fit values higher than 92%, including: formic acid (tR ¼
2:75 min), acetic acid (tR ¼ 3:27 min), benzaldehyde (tR ¼
9:62 min), benzoic acid (tR ¼ 13:81 min), and phthalic acid
(tR ¼ 17:25 min). All the identified compounds were organic
acids, which was accorded with the trait of organic compounds
in oxidative degradation. Meanwhile, TOC content of solution
reduced from 6.75 to 2.53 mg/L, achieving 62.5% CO2 forma-
tion within 80 min. Such high TOC removal indicated that both
degradation and mineralization of RhB continuity occurred in
FePz(dtnCl2)4/H2O2/visible light system, while high degrada-
tion rate and TOC removal of RhB were exciting in comparison
with that of some biomimetic photocatalysis systems under
similar condition.7,11
Hydrogen peroxide, is the ‘‘clean’’ oxidant for the degrada-
tion of persistent organic pollutants in water.1 The famous utiliz-
ed H2O2 system is Fenton reagent (FeII/H2O2), but it must be
held in acid solution (pH <3) and only ultraviolet light can en-
hance the reactive rate to degrade organic pollutants.2 To mimic
the structure of iron-containing oxygenase enzymes such as the
cytochrome P450, several synthetic analogous have catalytic
prosperity to activate H2O2 in an extensive pH range. For exam-
ple, Collins et al. synthesized an iron complex of tetraamidoma-
crocyclic (Fe-TAML), which can activate H2O2 in the dark
for rapid total destruction of 2,4,6-trichlorophenol (TCP).3,4
Meunier reported that chlorophenols in a CH3CN/water mixture
could be efficiently oxidized by H2O2 in the presence of iron–
phthalocyaninesulfonate (FePcS) in the dark, and iron–peroxo
species [Fe(OOH)(PcS)] was involved as an active oxygen
intermediate.5,6 Zhao’s group successfully introduced visible
ꢁ
light to FePcS/H2O2 system without adding CH3CN, and HO
radicals were detected as the active oxygen species,7 in which
the photodegradation for RhB or Orange II can proceed efficient-
ly in a wide pH range except for neutral solution.8
Control experiments of RhB degradation in the presence
of H2O2 are illustrated in Figure 2. This compound was only
slightly decomposed in the presence of H2O2 under visible light
Iron porphyrazines (FePz) and relative derivatives are also a
kind of N4-ligand complexes, which are of special prosperity in
biomimic catalysis and photoreaction.9,10 Herein, we reported a
novel photocatalyst of iron(II)–tetra(5,6-dichloro-1,4-dithin)-
porphyrazine [FePz(dtnCl2)4], with saturated solubility 7.9 mM
in water, which can efficiently activate hydrogen peroxide in ho-
mogeneous conditions to degrade toxic pollutants [Rhodamine
B(RhB), and 4-nitro benzoic acid(NBA)] under visible light
irradiation (ꢀ > 420 nm) and extensive pH range.
The reaction solution containing the catalyst of FePz-
(dtnCl2)4 and the substrate of RhB or NBA was first magnetical-
ly stirred in an 80-mL pyrex glass vessel over 2 min, then
H2O2 was added, and whole reaction system was irradiated with
a 500-W halogen lamp through a glass filter cutoff wavelength
less than 420 nm, while the intensity of light was ca. 29000
lux. The reaction was monitored by a Shimadzu UV-2450 spec-
trophotometer for RhB and a VARIAN ProStar 210 HPLC (C18
reverse column) for NBA. At the end, the reation residues were
treated with a headspace solid-phase microextraction (SPME) at
0 min
1.0
5 min
COOH
10 min
20 min
40 min
60 min
80 min
Cl
NEt
0.5
Et N
O
2
2
0.0
300
400
500
600
wavelength/nm
Figure 1. UV–vis spectra changes of RhB (10 mM, pH 2,
50 mL) in the presence of FePz(dtnCl2)4 (7.9 mM)/H2O2 (0.36
mM) under visible light irradiation (ꢀ > 420 nm).
Copyright ꢀ 2007 The Chemical Society of Japan
Sun, Jie
