Heterogeneous catalytic 2,4,6-trichlorophenol degradation at hemin–acrylic
copolymer
Goretti Dı
´
az-Dı
´
az, Marı
´
a Celis-Garcı
´
a, M. Carmen Blanco-Lo
´
pez, M. Jesu
´
s Lobo-Castan
˜
o
´
n,
Arturo J. Miranda-Ordieres, Paulino Tun
˜
o
´
n-Blanco
*
Departamento de Quı
´
mica Fı
´
sica y Analı
´
tica, Universidad de Oviedo, Julia
´
n Claverı
´
a, 8, 33006 Oviedo, Spain
1. Introduction
2,4,6-Trichlorophenol (TCP) and other chlorophenols constitute
a group of priority pollutants listed by the US Environmental
Protection Agency (EPA) in the Clean Water Act and by the
European Union (EU) in the Decision 2455/2001/EC. They have
been employed in the manufacturing of herbicides, fungicides,
pesticides, insecticides, pharmaceuticals and dyes. Chlorophenols
may be also generated as by-products during waste incineration,
the bleaching of pulp with chlorine and the dechlorination of
drinking water. They can be found in ground waters, wastewaters
and soils [1]. Their toxicity and persistence in the environment
increase with the degree of chlorine substitution. In particular, TCP
causes respiratory effects from cough to serious pulmonary
lesions.
Due to their high toxicity, carcinogenic properties and
persistence in the environment, several strategies have been
followed to remove them from the environment. Conventional
methods include thermal, chemical and biological treatments [2].
The biological methods are remarkable because of the environ-
mental availability and the low cost of the microorganisms, which
liveinmuds,sludges andsewages. However,microorganismsrequire
specific conditions to carry out their degradation reactions by
reductive dehalogenation route in anaerobic conditions or by an
oxidative pathway [3]. These factors include pH value, number of
microbes, viscosity [4], temperature, oxygen, water and nutrients
availability, and the presence of products from the decomposition of
roots.Ontheother hand,themajority ofchlorophenols arepoisonous
to microorganisms, so the direct use of biological treatment is not
effective in many cases. Sometimes an enzymatic pre-treatment is
advised before the subsequent microbiological step. Moreover,
depending on the biocatalyst, the reaction conditions and the
chlorophenol characteristics, the sole use of enzymes could result in
the formation of polymeric products that could be removed by
filtration [5,6] or even in the complete degradation to CO
2
and H
2
O.
Some enzymes (summarized in Table 1) have been used to degrade a
wide variety of chlorophenols and even 4-fluorophenol.
As it can be seen, the enzymes belong to the heme-peroxidases
and P450 cytochrome families, whose structures consist on
aminoacidic chains surrounding the active site, where the heme
molecule is housed. Therefore, heme-like iron catalysts involving
planar coordination of four nitrogen donor atoms may be adequate
to activate hydrogen peroxide toward chlorophenols oxidation.
Some of the reagents explored for homogeneus catalytic degrada-
tion involve porphyrins and phthalocyanines with diverse metal
centres or even without metal atoms as catalysts, as summarized
in Table 2.
Applied Catalysis B: Environmental 96 (2010) 51–56
ARTICLE INFO
Article history:
Received 9 December 2009
Received in revised form 20 January 2010
Accepted 30 January 2010
Available online 6 February 2010
Keywords:
2,4,6-Trichlorophenol
Degradation
Heme-catalyst
Acrylic polymer
ABSTRACT
The synthesis, characterization and evaluation of the catalytic properties of a hemin–methacrylamide–
ethylene glycol dimethacrylate copolymer are described. This polymer catalyzes the oxidative
dechlorination of 2,4,6-trichlorophenol (TCP) in the presence of hydrogen peroxide, yielding 2,6-
dichloro-1,4-benzoquinone as the main reaction product. This low-cost material allows the complete
removal of TCP from water at concentration level of 20 mg L
À1
in less than 30 min.
ß 2010 Elsevier B.V. All rights reserved.
Abbreviations: MA, methacrylamide; EGDMA, ethileneglycoldimethacrylate; AIBN,
2,2
0
-azo-bis-(isobutyronitrile); DMSO, dimethylsulfoxide; 2-CP, 2-chlorophenol; 3-
CP, 3-chlorophenol; 4-CP, 4-chlorophenol; 2,4-DCP, 2,4-dichlorophenol; 2,6-DCP,
2,6-dichlorophenol; TCP, 2,4,6-trichlorophenol; 2,3,5,6-TeCP, 2,3,5,6-tetrachloro-
phenol; PCP, pentachlorophenol; 4-FP, 4-fluorophenol; DCQ, 2,6-dichloro-1,4-
benzoquinone.
* Corresponding author. Tel.: +34 985103487; fax: +34 985103125.
E-mail address: ptb@uniovi.es (P. Tun
˜
o
´
n-Blanco).
Contents lists available at ScienceDirect
Applied Catalysis B: Environmental
journal homepage: www.elsevier.com/locate/apcatb
0926-3373/$ – see front matter ß 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.apcatb.2010.01.032