Reduction of hexavalent chromium by polypyrrole-modiﬁed
steel mesh electrode
, Fenglin Yang
School of Environmental and Biological Science and Technology, Dalian University of Technology, China
School of Environmental Science and Engineering, Dalian Jiaotong University, Dalian, China
Received 15 August 2005; accepted 3 April 2006
Available online 24 May 2006
Adherent polypyrrole (ppy) ﬁlms were electropolymerized from a para-toluenesulfonic sodium (PTS) solution on stainless steel mesh (SSM).
Reduced ppy-modiﬁed SSM electrode can transfer Cr(VI) to Cr(III) effectively. Lower pH (<2) or higher temperature (>35
C) is beneﬁcial
for the removal of Cr(VI). Electro-reduction achieved 90% removal efﬁciency after 21 min by cyclic voltammetry. The removal efﬁciency is
96e56% for oneesix contact cycles between ppy and Cr(VI). SEM shows that ppy ﬁlms on SSM have regular morphology with small nucleus
of less than 1 mm in diameter.
Ó 2006 Elsevier Ltd. All rights reserved.
Keywords: Polypyrrole; Stainless steel mesh; Reduction; Cr(VI)
Hexavalent chromium is generated from a variety of
processes and its potential harm such as toxic, carcinogenic
and extremely mobile causes public concern. Many traditional
methods have been used for the removal of hexavalent chro-
mium from the environment. But each one has its own merits
and limitations. For example, chemical treatment can produce
amounts of sludge by the use of reducing agents, such as
sulﬁte, hydrogen sulﬁte and ferric bisulﬁte. Ion exchange is
an effective method by exchange dichromate with removable
anions in resin substrate. However, resin regeneration can
produce a great deal of waste alkali solution which will cause
Polypyrrole is a kind of conducting polymer and its redox
property made it possible to be an alternative regent when
reduced polypyrrole reacts with dichromate. It can reduce
Cr(VI) to Cr(III) and it is oxidized. The oxidized polypyrrole
can be electrochemically recycled to the reduced state for
another treatment cycle.
Polypyrrole can be easily deposited on a variety of conduct-
ing electrode substrates. Alatorre et al. studied the reduction of
hexavalent chromium by polypyrrole deposits on different
substrates . Rodriguez et al. focused on the inﬂuence of
anions and other experimental conditions during the prepara-
tion of ppy ﬁlms on reticulated vitreous carbon substrate .
Conroy and Breslin reported the reduction of hexavalent chro-
mium at a polypyrrole-coated aluminum electrode .
In this paper stainless steel mesh is chosen as a substrate on
which ppy was electrochemically synthesized. Because of its
low cost and easily being cut to any shape and size, ppy-modiﬁed
stainless steel is very much possible to a large scale application.
Stainless steel mesh (SSM) of 80 pores per inch (ppi)
and dimensions of 25 Â 60 mm were rinsed in acetone and
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E-mail address: firstname.lastname@example.org (F. Yang).
0959-6526/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
Journal of Cleaner Production 15 (2007) 1415e1418