Green synthesis of potassium zinc hexacyanoferrate nanocubes and their potential application in photocatalytic degradation of organic dyes

Article abstract of DOI:10.1039/c5ra03266k

A novel green route was used to synthesize potassium zinc hexacyanoferrate (K₂Zn₃[Fe(CN)₆]₂·9H₂O) (KZnHCF) nanocubes using Sapindus mukorossi as a natural surfactant and water as the solvent. The synthesized nanoparticles were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric techniques and BET surface area analysis. KZnHCF nanoparticles were investigated for their effect on the photocatalytic degradation of two synthetic dyes namely Eriochrome Black T (EBT) and Malachite Green (MG). The effect of process parameters like pH, temperature, KZnHCF dose and concentration of the dye on KZnHCF mediated degradation of both dyes was also investigated. Under optimized conditions, KZnHCF resulted in 94.15% degradation of MG followed by 76.13% EBT degradation.

Full text of DOI:10.1039/c5ra03266k

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Title of the Paper:
Green Synthesis of potassium zinc hexacyanoferrate nanocubes and its
potential application in photocatalytic degradation of organic dyes
Vidhisha Jassala, Uma Shankera* B S Kaitha and Shiv Shankarb
jassalvidhisha@gmail.com, shankeru@nitj.ac.in, kaithbs@nitj.ac.inshiv.nature@gmail.com ,
aDepartment of Chemistry, Dr B R Ambedkar National Institute of Technology
Jalandhar, Punjab, India-144011
bDepartment of Environmental Science, Babasaheb Bhimrao Ambedkar University,
Lucknow, India-226025
* Corresponding Author
Dr Uma Shanker (Assistant Professor)
CE-306
Dept of Chemistry
Dr B R Ambedkar National Institute of Technology Jalandhar, India-144011
Email: shankeru@nitj.ac.in, umaorganic29@gmail.com
Contact number: +91- 7837-588-158 (Mobile)
+91-0181-269-301-2258
Fax: +91-0181-269-0932
1

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Abstract
A novel green route was used to synthesize potassium zinc hexacyanoferrates
(K2Zn3[Fe(CN)6]2.9H20) (KZnHCF) nanocubes using Sapindus mukorossi as natural
surfactant and water as solvent. The synthesized nanoparticles were characterized by Powder
Xꢀray diffraction (PXRD), Scanning electron microscopy (SEM), Transmission electron
microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric
techniques and BET surface area analysis. KZnHCF nanoparticles were investigated for their
effect on photocatalytic degradation of two synthetic dyes namely Eriochrome Black T (EBT)
and Malachite Green (MG).The effect of process parameters like pH, temperature, KZnHCF
dose and concentration of dye on KZnHCF mediated degradation of both dyes was also
investigated. Under optimized conditions, KZnHCF resulted in 94.15% degradation of MG
followed by 76.13% EBT degradation.
Keywords: Potassium zinc hexacyanoferrate, Natural biosurfactant (Sapindus mukorossi),
nanocubes, Eriochrome Black T (EBT), Malachite Green (MG), photocatalytic degradation.
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1. Introduction:
Metal hexacyanoferrates (MHCF) with general formula Mk[Fe(CN)6]·xH2O represent an
important class of coordination compounds, where k represents stoichiometric number [1].
Over the last few decades such compounds have gained attraction all over the world because
of their peculiar physicochemical properties like electrochromism [2,3], photo
electrochromism [4], energy storage [5,6], electrolytic and sensing properties [1,7] through
molecular architecture.
ZnHCF differs from other Prussian blue (PB) analogues because of certain unique properties
like Zn has completely filled 3d as well as 4s orbitals and narrow band gap. Moreover,
ZnHCF can be formed only in a certain ratio of the modification species.
Electrocrystallization phenomenon has been found to be predominant over stable surface
modification [8].ZnHCFis a unique exception as it does not get deposited easily on surfaces
like glassy carbon (GC), Pt and Au [8,9, 10].
Because of shape and size dependent properties of ZnHCF nanoparticles, their use as a
semiconductor in the photocatalytic degradation of various harmful dyes has drawn the
attention of Scientific fraternity for the applications of such nanoꢀcoordination compounds in
the treatment of textile and other related industrial effluents.
Synthetic dyes are extensively used in the textile industries and as per report worldwide
2,80,000 tons of textile dyes are discharged in industrial effluents every year [11]. Discharge
of untreated effluents under anaerobic conditions causes formation of toxic aromatic amines in
receiving water bodies. Since synthetic dyes are toxic, mutagenic and carcinogenic [12] and
increase the COD, therefore, efficient removal of dyes from industrial effluents is a major
environmental challenge [13,14].
Malachite green (MG) a water soluble synthetic textile dye [17] because of its toxic effects
has become one of the most controversial dyes [18, 19]. It provides undesirable color to the
water bodies and reduces sunlight penetration, thereby effecting the lives of several aquatic
species [20,21]. On the other hand, anionic Eriochrome Black T (EBT) has the share of more
than 50% of the global dye production [22]. Its complex molecular structure and resistance to
light, water and chemicals is one of the major environmental problem [22,23].
During last few decades development of clean and efficient water purification technology has
been the focus of research. Nanoparticle mediated heterogeneous photodegradation has
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emerged as one of the most powerful methods of water decontamination because of its
potential to transform recalcitrant organic contaminants in to mineral salts and relatively
innocuous end products like CO2 and H2O [1, 15, 16].
Moreover, natural nonꢀionic biosurfactants are emerging as ecoꢀfriendly and efficient
materials for the synthesis of nanoparticles [24,25,26].Saponins,one of the most commonly
used biosurfactants is largely found in plants like Sapindus mukorossi, Quillaja bark [27],
soyabean [28] and Fagonia indica [29]. Rithanuts obtained from the trees of Sapindus
mukorossi in its powdered state is one of the major ingredients in theherbal products like
fabric washings, bath soaps, shampoos, hair dyes and bodyꢀcare lotions [30].
At critical miscellar concentration such bioꢀsurfactants tend to form miscelles and assist in the
synthesis of different types of nanoꢀstructures. Sapindus mukorossi belongs to the plant family
Sapindaceae and order Sapindeae. Nut powder of this plant is nonꢀionic natural biosurfactant
which contains about 6 to 10 wt% of Saponin [31]. Saponins are widely used in
pharmaceuticals [32, 33], detergents [34] and environmental remediation [35].
In present study, a novel ecoꢀfriendly method for the synthesis of potassium zinc
hexacyanoferrate nanocubes was developed using bioꢀsurfactant.To the best of our
knowledge, so far no studies have been reported using Sapindus mukorossi (raw ritha) as a
natural surfactant for the synthesis of zinc hexacyanoferrate nanoparticles. The effect of
potassium zinc hexacyanoferrates on photocatalytic degradation of Malachite green (MG) and
Eriochrome Black T (EBT) was investigated. The process parameters favoring maximum
degradation of these two synthetic dyes were also optimized.
2. Experimental details
2.1 Materials:All reagents used in the study were of analytical grade. Potassium
hexacyanoferrate (II), zinc salt, Eriochrome Black T and Malachite Green were purchased
from Merck, India Ltd. Sapindus mukorossi was purchased from Jalandhar city, Punjab India.
2.2 Synthesis of potassium zinc hexacyanoferrate nanoparticles:
Bioꢀsurfactants are surface active agents produced by plants or microorganisms. Using the
same mechanism as chemical surfactants, they are able to reduce the surface and interfacial
tension, thereby reducing the size of the particles. They have several unique features which
makes them a promising alternative to chemically synthesized surfactants. These include
stable activity at extreme pH, higher biodegradability than chemical surfactants which remains
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as such, thus leading to environmental pollution. So, these bioꢀsurfactants are ecoꢀfriendly.
Also, they have negligible toxicity. On the other hand, most of the chemical surfactants are
produced by petroleum feed stocks, hence more toxic and less biodegradable. Since the bioꢀ
surfactants like sapindus mukorossi used by authors, are biodegradable and have negligible
toxic effect on the environment, thus the synthesis of KZnHCF nanocubes employing
sapindus mukorossi can be called as ‘green synthesis’.
Here, we report the green synthesis of potassium zinc hexacyanoferrate nanoparticles using
Sapindus mukorossias a biosurfactant. 100 ml solution of 0.1M potassium hexacyanoferrate
(II) containing an equimolar amount of potassium chloride was slowly added to a 100 ml
solution of 0.1M ZnCl2 containing an equimolar amount of Sapindus mukorossi with constant
stirring. An excess of metal salt was used to improve the coagulation of the precipitate. The
reaction mixture was heated at 60 0C on water bath for 2–3 hours and finally kept undisturbed
for 24 hours at ambient temperature. The precipitates were filtered, washed thoroughly with
double distilled water and dried in oven at 60 0C.
2.3 Characterization
The synthesized nanoparticles were characterized using various techniques like Powder Xꢀray
diffraction (PXRD) which was recorded with a P analytical Xpert Pro spectrometer using Cu
Kα1 radiation (wavelength 1.540 Å). In order to investigate the surface morphology and
average particle size of the synthesized nanoparticles, Scanning electron microscopy (SEM)
was carried out. The elemental composition was determined using Energy dispersed
spectroscopy (EDS). Transmission electron microscopy (TEM) gave information regarding
exact particle size and shape of the nanoparticles. Fourier transform infrared spectroscopy
(FTꢀIR) was also performed to understand the bonding present in the coordination complex.
The BET (Brunauer ꢀEmmett –Teller) surface area measurement was done using a BET N2ꢀ
physisorption instrument (Nova Station A, Quantachrome Nova Win instrument, version
10.01). The N2 adsorption was measured at 77.3 K with the assumption of crossꢀsectional area
of N2 16.2 (Ǻ)2 and liquid density as 0.808g/cc.
2.4 Photocatalytic degradation
Photodegradation experiments were performed with a photocatalytic reactor system to
degrade MG and EBT. The benchꢀscale system is a cylindrical Pyrexꢀglass cell with 1.0 L
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capacity, 10 cm inside diameter and 15 cm height. Irradiation experiments were performed
using medium pressure Hg lamp. A magnetic stirrer was used continuously to guarantee good
mixing of the solution. The aliquot was taken out at different time intervals. To check the
catalytic activity of K2Zn3[Fe(CN)6]2.9H20 nanocubes different parameters such ascatalyst
concentration, initial concentration of dye, initial pH and temperature of the dye solution were
investigated. The absorption spectra of the dye solutions were recorded using Agilent Pro
spectrometer and the rate of degradation was observed at different time intervals in terms of
change of intensity at λmax i.e 615ꢀ619 nm (MG) and 560 nm (EBT). The dye degradation
efficiency (%) has been calculated as:
ꢀꢂꢃ − ꢂꢁ
ꢀ ꢁ
Degradation efficiency % =
× 100
ꢂꢃ
Where ꢂꢃ is the initial concentration of dye and C is the concentration of dye after photoꢀ
irradiation at particular time interval.
3. Results and discussion:
Chandra et al. [36] reported the octahedral geometry of [Fe(CN)6]4ꢀwith six CNꢀ ligands
surrounding the central metal ion. CNꢀ ligands being strong field ligands will forcefully get
paired up the 6 electrons present in the inner sphere of Fe2+ and a lowꢀspin t2g6 configuration is
achieved. Moreover, there is a significant backꢀbonding between the metal dπ orbitals to the
antibonding pπ orbitals of the CNꢀ ligands. The outer sphere metal Zn metal is coordinated to
the Nitrogen end of the cyanide ligand present inside the [Fe(CN)6]4ꢀ anionic sphere.
Powder Xꢀray diffraction measurements (Powder Method, Analytical X.Pert Pro) were carried
out (Figure 1). Interplanar spacing and the relative intensity data were found in good
agreement with the JCPDS values (JCPDS card No 33ꢀ1061). The clear and sharp Xꢀray peaks
indicated the high crystallinity of synthesized nanomaterial
.
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Figure 1: XRD pattern of K2Zn3[Fe(CN)6]2.9H2O
The surface morphology of Potassium zinc hexacyanoferrate nanostructures was evaluated by
field emission scanning electron microscopy (FESEM, QUANTA 200 FEG)which revealed
that the synthesized products were monodispersed nanocubes with size ranging from 33 to
192 nm (Figure 2), however, slightly agglomerated particles were observed during its
morphological investigations. To examine the elemental composition, the synthesized
nanocubes were analyzed by energy dispersive spectroscopy (EDS) which showed the
presence of Zn, Fe, N, C and K with atomic percentage 8.32%, 5.83%, 41.03%, 39.93% and
4.89%, respectively.
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Figure 2: FEꢀSEM image with Elemental composition (EDS) pattern of
K2Zn3[Fe(CN)6]2.9H2Onanocubes
To investigate the exact size and shape of synthesized potassium zinc hexacyanoferrate
nanoparticles TEM (Hitachi, Hꢀ7500) was employed (Figure 3). Interestingly, potassium zinc
hexacyanoferrates have been found to be consisting of the uniform monodisperse cubic shape
nanostructures with size ranging around 100 nm. Morphology was clear and well dispersed
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with sharp nanocubes. However, slight agglomeration was also observed among the cubical
nanoparticles.
Figure 3: TEM images of K2Zn3[Fe(CN)6]2.9H2Onanocubes
FTꢀIR studies were also carried out (Figure 4) to determine the various functional groups
present in the synthesized products. It is well known that the single, broad band of the νCN
absorption of PBꢀstructured materials in the range of 2000–2200 cm−1 is diagnostic of the Cꢀ
bound metal ion and its oxidation state, but is much less sensitive to the Nꢀbound metal ion
and its oxidation state. Peak below 400 cmꢀ1 corresponds to the metal ion peak. Its frequency
varies depending upon the transition metal ion. In case of potassium zinc hexacyanoferrate
nanocubes, C N group present in the species shows a strong peak at 2090 cmꢀ1 whereas
peak corresponding to ZnꢀN is observed at 491 cmꢀ1. Also, a broad peak at 3631 cmꢀ1 is due to
the presence of OH moiety from water molecules. Peak at 1614 cmꢀ1 is due to HOH bending.
Lastly, peak at 602 cmꢀ1 corresponds to FeꢀC stretching.
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100
90
80
70
60
50
40
30
20
1
2335
990
3631
1614
602
491
2090
2000
3800
3600
3400
3200
3000
2800
2600
2400
2200
Wavenumber
1800
1600
1400
1200
1000
800
600
400
Figure 4: FTꢀIR spectra of K2Zn3[Fe(CN)6]2.9H2O nanocubes
Thermal analysis showed that potassium zinc hexacyanoferrate nanoparticles
0
(K2Zn3[Fe(CN)6]2.9H20) decomposes slowly on heating to 100 C and it decomposes at
0
0
relatively a higher rate from 100 C to 203.2 C. The mass loss was nearly 12.6% upto 203.2
0C. This weight loss could be referred to the loss of water of crystallization. No significant
0
mass loss was observed upto 420 C, but after that a drastic loss was found when heating the
0
0
compound from 420 C to 734 C (nearly 29% wt. loss). The additional loss in weight could
be due to the removal of cyanide moiety. Around 40% of the residue remained at the end of
the experiment (Figure 5). Possible mechanism could be described as shown below:
115.0
711.1C el
0.159m g/m in
0.500
0.000
424.6C el
0.329m g/m in
110.0
105.0
100.0
95.0
90.0
85.0
80.0
75.0
70.0
65.0
60.0
0.200
0.000
0.209m g/m in
0.110m g/m in
423.7C el
0.126m V
-0.500
-1.000
-1.500
-2.000
-2.500
-3.000
-3.500
-4.000
0.070m V
101.3Cel
92.9%
4.7%
-0.200
-0.400
-0.600
-0.800
-1.000
203.2C el
85.1%
421.2C el
82.8%
7.9%
2.2%
527.0C el
14.2%
68.7%
734.6C el
60.3%
8.4%
100.0
200.0
300.0
400.0
500.0
600.0
700.0
Tem p Cel
Figure 5: Thermal analysis of K2Zn3[Fe(CN)6]2.9H2Onanocubes
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100-203.2 0C
K2Zn3[Fe(CN)6]2.9H20
K2Zn3[Fe(CN)6]2.3H20
nearly 12.6 %
-6H20
203.3-420 0C
No significant loss
420-734 0C
K2Zn3[Fe(CN)]2.2H20
K2Zn3[Fe(CN)6]2.3H20
nearly 29%
-5CN, -1H20
Figure 6: Proposed scheme for the weight loss during TGA
The specific surface area of KZnHCF nanocubes was calculated using the MultiꢀPoint BET
surface area analysis technique and was found to be 50.919 m2/g. Using this value of surface
area, average equivalent particle size can be calculated by using the equation DBET
=
6000/(ρ.Sω), where DBET is the average diameter of the particle (in nm), Sω represents
measured surface area of the nanoparticles in m2/g and ρ is the theoretical density in g/cc.
From the above equation, average diameter of the particle was calculated as 145.87 nm, which
is in well agreement with the TEM results. The Langmiur surface area, total pore volume and
average pore radius was found out to be 72.372m2/g, 4.600eꢀ02 cc/g and 1.32317e+02 Å,
respectively.
Photocatalytic activity
In order to evaluate the photocatalytic effect of potassium zinc hexacyanoferrate nanocubes in
the degradation of MG and EBT, measurement of absorbance at regular time intervals was
carried out. Two different processes are occurring throughout the reaction on the surface of
photocatalyst i.e KZnHCF nanocubes. When the dye solution was exposed to light in the
presence of KZnHCF nanocubes, the first step may be dye adsorption on the surface of the
catalyst (KZnHCF nanocubes), confirmed by Langmuir adsorption isotherms. Then, catalyst
also absorbs the light to excite its electron from valence band to conduction band, thereby
leaving behind a hole. The in situ generated hole reacts with the water molecules present in
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the dye solution and converts it into very reactive hydroxyl free radical (OH•). These free
radicals (OH•) then reacts with the dye molecules to generate colourless form of the dye,
which is ultimately degraded into final colourless products.
Different parameters such as photocatalyst dose, initial concentration of dye, initial pH and
temperature of the dye solution were studied for getting the maximum dye degradation. The
prime motive behind these choices was to achieve maximum degradation of these two harmful
organic dyes i.e. MG and EBT. Since the effluents from dyestuff and textile industries, which
are the major sources that release various kinds of dyes into the water bodies, reach water
bodies, thus, pH and temperature of water as well as dye concentration is an essential
parameter to be investigated. Moreover, amount of catalyst required to degrade these harmful
organic dyes is an important criteria. So, the authors decided to investigate the above
mentioned four parameters for achieving maximum degradation of MG and EBT dye.
Absorbance was recorded after each interval of 20 minutes and carried out upto 2 hours.
Absorbance intensity was found to decrease continuously with increase in time interval and
maximum degradation of MG (94.15%) and EBT (76.13%) was observed at 2 hr interval. It
may be due to the reason that catalyst used is a semiconductor which upon photo illumination
generates electronꢀhole pairs. The generation of electronꢀhole pairs is responsible for the
photodegradation of MG and EBT. Further the photodegradation of both MG and EBT was
found to be initial dye concentration dependent. In both cases maximum photocatalytic
degradation was observed at 5ppm concentration. The possible explanation could be at this
dye concentration maximum number of active sites on potassium zinc hexacyanoferrate are
available for adsorption of dyes. As the concentration increases, the active sites for adsorption
present on nanocubes get blocked, thus the rate of dye degradation decreases. In case of
temperature dependent dye degradation studies, it was found that with increase in temperature,
relative absorption intensity decreased and negligible dye degradation was oberved. Thus,
potassium zinc hexacyanoferrate nanocubes in case of MG and EBT degradation act as a
photocatalyst not thermocatalyst. However, photodegradation of both the dyes was found to
be dependent upon the concentration of potassium zinc hexacyanoferrate nanocubes. At the
concentration of 15mg of nanocubes per 10 ml of dye solution maximum photodegradation of
94.15% and 76.13% was found in case of MG and EBT, respectively. This could be due to the
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reason that at low dye concentration which was optimized earlier, too high and low dose
amounts of the catalyst was not a favourable condition. A moderate condition i.e. 15 mg of the
catalyst was favoured for the best decomposition of MG and EBT. In case of MG and EBT
adsorption and their photocatalytic degradation pH was found to play an important role.
Photocatalytic degradation was found to increase with increase in pH. However, maximum
adsorption and degradation was found at pH 7. Further increase in pH resulted in decreased
dye adsorption and degradation. This could be due to the ion screening effects of H+ ions
under acidic conditions and OHꢀ ions in alkaline medium. KHCF nanocubes are insoluble in
water as well as fairly stable in acids like HCl, HNO3, H2SO4 as well as bases like NaOH,
KOH etc. Thus, after the completion of reaction, catalyst was recovered and used again for
similar reactions.
Figure 7: Effects of variation of different parameters on the photocatalytic degradation of
EBT and MG dyes.
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Reaction mechanism studies
Adsorption isotherm (Figure 8) of MG and EBT in the present case clearly shows that
adsorption is fast in both the cases and the isotherms are regular, positive, and concave to the
concentration axis. Adsorption data can be represented through a Langmuir adsorption
isotherm which assumes the formation of a monolayer of solute molecules on the surface of
the adsorbent [37]. A typical graph of Ce/Xe v/s Ce is a straight line (Where Ce Equilibrium
concentration of solute in mole/l and Xe amount of solute adsorbed per gram weight of
adsorbent (mg) (Figure 9). The adsorption data was fitted in Langmiur adsorption equation:
ꢄ
ꢇ
ꢄ
ꢅ
ꢅ
=
+
ꢆ
ꢊ
ꢆ
ꢅ
ꢈ ꢆ
ꢉ
ꢊ
or
1
1
1
1
=
ꢍ
ꢑ +
ꢋꢌ ꢂꢌ ꢎꢏꢋꢐ
ꢋꢐ
Where, Ce is the equilibrium concentration of the dye solution; Xe the amount of dye adsorbed
per gram weight of adsorbent; Xm the amount of dye adsorbed at saturation; kL the langmiur
adsorption constant.
kL and Xm values were determined and shown in Table 1. The Xm values indicate that MG
adsorbed more than EBT on potassium zinc hexacyanoferrate nanoparticles. It may be due to
more availability of N atoms of MG for interaction with potassium zinc hexacyanoferrate
nanoparticles.
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3.5
3.0
2.5
2.0
1.5
1.0
EBT
MG
0
5
10
15
20
25
30
Concentration (ppm)
Figure 8: Adsorption isotherm for adsorption of dyes on potassium zinc hexacyanoferrate
nanoparticles
6
MG
EBT
5
y=0.17998x+0.13346
4
3
y= 0.15941x+0.54307
2
1
0
0
5
10
15
20
25
30
-6
[Dye]/10 M
Figure 9:Langmuir isotherms for adsorption of MG and EBT on potassium zinc
hexacyanoferrate nanoparticles
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Table 2. Langmiur constants for MG and EBT adsorption on potassium zinc hexacyanoferrate
nanoparticles
Dye
MG
EBT
Xm(mg/g)
6.273
KL(dm3/mol)
3.406
5.556
0.7415
From the literature survey it was observed that potassium zinc hexacyanoferrate is
semiconducting with a lesser band gap difference [38, 39], so molecular excitation occurs very
easily with a light of equal or higher energy than the brefand gap, thereby generating electrons
and holes in between conduction and valence bands. This followed by a series of chemical
reactions leading to the formation of hydroxyl radicals. It is the OH• which leads to the
photodegradation of harmful organic dyes. The following reaction sequence is proposed for
the degradation of dyes in presence of KZnHCF nanocubes (Figure 10 and 11):
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*
N
N
N
N
+ h
Malachite Green (MG) dye
MG Dye (excited state)
K2Zn3[Fe(CN)6]2.9H20 (e- CB + h+VB)
+ h
K2Zn3[Fe(CN)6]2.9H20
h+ + H20
*
H+ + OH
OH
N
N
N
N
+ OH
MG Dye (excited state)
MG Dye (colourless form)
OH
N
N
Degradation products (CO2, H20)
MG Dye (colourless form)
Figure 10:Photocatalytic degradation of MG in presence of KZnHCF nanocubes
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Figure 11: Photocatalytic degradation of EBT in presence of KZnHCF nanocubes
4. Conclusions
Monodisperse potassium zinc hexacyanoferrate nanocubes using Sapindus Mukorossi as a
biosurfactant were synthesized through a novel green route. Synthesized nanocubes were
evaluated as photocatalyst for the degradation of MG and EBT. Different process
parameters like photocatalyst doze, initial dye concentration, pH and temperature were
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studied in order to get the maximum dye degradation. MG was found to get degraded to
the extent of 94.15% and EBT to 76.13% at pH, 7.0; ZnHCF, 15 mg; MG and EBT, 5ppm
and temperature, ambient. Thus, the potassium zinc hexacyanoferrate nanocubes are the
promising agents for the treatment of dyes contaminated industrial effluents.
5. Acknowledgement: One of the authors Ms. Vidhisha Jassal is thankful to Ministry of
Human Resource and Development (MHRD), New Delhi for providing financial
assistance. Authors are also thankful to FISTꢀDST, New Delhi for providing the
equipment (FTꢀIR and UVꢀVIS) used in characterization of the samples.
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