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z Energy Technology & Environmental Science
Synthesis of a Highly Efficient Multifunctional Copper
(II)-Pyridyl Complex for Adsorption and Photocatalytic
Degradation of Organic Dyes
Harshita Jain,
[a]
Ankita Joshi,
[b]
C. N. Ramachandran,
[b]
and Rakesh Kumar*
[a]
A new copper (II) pyridyl complex CP1, has been synthesized
for adsorption as well as photocatalytic degradation of
Methylene Blue (MB) and Rhodamine B (RhB) dyes and
characterized through FT-IR, LC–MS, FE-SEM, TEM and EPR
studies. The density functional theoretical (DFT) study was
performed to determine the mode of binding of Cu
II
ions with
ligand 1 to form complex CP1. Photoluminescence study in
solid state suggests that CP1 could act as potential green light
emitter. The adsorption of MB and RhB dyes on the surface of
CP1 is found to depend on adsorbent dosage, initial concen-
tration of dyes and contact time. In addition, adsorption of
dyes on CP1 is found to follow Freundlich adsorption isotherm
and pseudo-second order kinetics. The photocatalytic degrada-
tion was performed under visible light irradiation which reveals
that 95.8% of MB (16 mgL
1
) and 93.7% of RhB (23.95 mgL
1
)
can be decolorized in 35 minutes using 0.3 gL
1
of catalyst. To
determine the intermediates formed during photocatalytic
degradation of dyes, LC–MS spectra is also obtained. From the
LC–MS spectra, intermediates are identified and mechanism of
degradation of dyes has been proposed.
Introduction
Over the last few decades, rapid growth of industrialization has
led to critical environmental problems in the form of water
pollution. The mutagenic and carcinogenic organic dyes used
in pharmaceuticals, textiles, printing, plastic, food and cosmet-
ics industries are released into the water bodies which pose
serious risks to human health, aquatic life and environment.
[1]
Their removal from water is challenging task owing to their
good solubility and high stability. Rhodamine B, an industrial
colorant has been classified as Group 3 carcinogen by IARC in
1987.
[2]
Rhodamine B, once absorbed becomes difficult to
remove from the body. It can be proved as carcinogenic and
neurotoxic inducer if ingested as it affects the functioning of
DNA. Another industrial colorant is methylene blue which
causes various health problems such as nausea, vomiting,
sweating and gastrointestinal problems. Therefore, treatment
of industrial water is essential prior to their discharge into the
water bodies.
Various approaches have been implemented for eliminating
dyestuffs from water such as physical adsorption, photo-
catalysis, chemical and membrane technologies, bioremedia-
tion, photocatalytic oxidation and Fenton oxidation.
[3–6]
The
most common method among the aforementioned methods is
adsorption which depends upon surface area, porosity and
host-guest interactions. Various adsorbents have been explored
for removal of dyes such as activated carbons,
[7]
carbon
nanotubes
[8,9]
and polymeric materials.
[10]
Photocatalytic degra-
dation using semiconductors is another most effective method
for degradation of dyes.
[11–13]
These methods are most versatile
on account of high efficiency, recyclability, low cost, and
generation of non-toxic degradation products. TiO
2
is the most
widely explored photocatalyst for photocatalytic degradation
of organic dyes. However, due to high band gap energy
(3.2 eV), TiO
2
absorbs only UV irradiation which limits its
practical application.
[14,15]
The development of inexpensive,
stable, efficient and band gap tuneable photocatalyst is still a
big challenge.
Recently, the design and synthesis of transition metal
complexes has attracted immense interest of researchers due
to their fascinating architectures, flexible redox properties and
potential applications in adsorption, sensing, catalysis, photo-
catalysis, magnetics, electronics, photoluminescence, pharma-
ceutics etc.
[16–20]
Compounds based on heterocycles such as
pyridine, imidazole, benzimidazole etc., have been employed
for construction of complexes for application in adsorptive
removal and photocatalytic degradation of organic dyes.
[21–24]
Metal organic complexes such as metal-porphyrin has been
used for degradation of toxic dyes.
[25,26]
H.Y. Ping et al. have
reported synthesis of Cu-Schiff base complex for degradation
of toxic organic pollutants. However, low efficiency and use of
H
2
O
2
(hazardous to skin, eyes and lungs) often limits their
application.
[27]
There are only few reports on Cu-Schiff’s base
complexes for application in adsorption or photocatalytic
degradation of dyes. The Cu-Schiff’s base complexes can be an
alternative to the expensive photocatalysts based on platinum,
ruthenium, gold and silver. Therefore, there is need to develop
different types of copper-based complexes having narrow band
gap for absorption of visible light.
[a] H. Jain, Dr. R. Kumar
Department of Chemistry, University of Delhi, Delhi-110007, India
E-mail: rakeshkp@email.com
[b] A. Joshi, Dr. C. N. Ramachandran
Department of Chemistry, Indian Institute of Technology Roorkee-
Uttarakhand-247667, India
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/slct.201900498
Full Papers DOI: 10.1002/slct.201900498
4952 ChemistrySelect 2019, 4, 4952 – 4961 © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim