Paper
RSC Advances
removal of methylene green in 6 to 10 min using a hetero- inorganic additives and diluted according to the requirement of
junction photocatalyst, namely, Ag PO @MWCNTs@Cr:SrTiO
3
under natural solar radiation and visible light irradiation.
the experiment. During the experiment, the concentration of
dye in the aqueous solution was determined by comparing the
3
4
The current practices of textile dye wastewater remediation visible range spectrum with the standard solutions via a Shi-
and minimization are a severe threat due to the risk associated madzu 1800 UV-Vis spectrophotometer. The wavelength
with its color to the running water streams. The usual maximum (lmax) of CR was 497 nm.
management procedures involved in textile wastewaters are
elimination by activated carbon adsorption, coagulation/ following equation:
occulation, and membrane separation (ultraltration, reverse
The percent de-coloration of CR was determined by using the
A
o
ꢀ A
t
Percentage of Decoloration ¼
(1)
osmosis), but these processes are not the comprehensive solu-
tion of the removal of pollutants, while a biological treatment is
not an exact solution due to the biological resistance of some
A
t
14–18
HPLC analysis of the degraded dye product. The degraded
product of CR was subjected to HPLC analysis for the validation
of UV spectral analysis. The dye solution before and aer the
accomplishment of reaction was analyzed by the reversed-phase
HPLC technique, where each sample was ltered through a 0.45
mm lter and then, 20 mL of the volume was loaded to HPLC,
equipped with a C-18 column (250 mm ꢁ 4.6 mm). The mobile
phase was prepared by using acetonitrile and water (HPLC
grade) in a ratio of 65 : 35, followed by ltration through a 0.45
mm lter and degassed with the help of ultrasonic waves before
use. The elution time of the Congo red dye was reported to be
dyes.
Thus, the dye wastewater management requires ultra-
advanced processes for the recovery of colored water with the
elimination of all relative byproducts by using the developed
method. Therefore, for this purpose, the oxidizing agent KMnO
4
was used due to its preventive nature instead of any other
compound of a high oxidative potential for the preservation of
water bodies. Mn is an essential micronutrient for both plants
and animals and can be easily removed/consumed by a marine
organism. The aims and objectives of this innovation were to
develop an ultra-advanced oxidation method for the recovery of
thousands of tons of water discharged during dyeing and n-
ishing processes with a lot of chemical additives used during
dye fabrication. For this purpose, Congo red was selected, and
the kinetics were monitored at various operational parameters
for the establishment of the mechanism of dye degradation in
the presence of all the dye fabricated additives. The application
of current ACOP is discussed in the relative section of this
article using real dye water samples with several other dyes.
2
.9 min. The analysis was performed on the isocratic system,
where the mobile phase was set at the ow rate of 1 mL min
ꢀ1
and the absorbance was recorded at 495 and 278 nm through
19
a deuterium lamp.
Analytical analyses. The mineralization of CR was deter-
mined by chemical oxygen demand (COD) of the de-colorized
ltrate by using the standard method stated in (APHA, 2005)
and COD analyzer APHA 5220 C. The COD values of both acidic
ltrate and it's neutralized form were calculated and compared
with the literature value of CR wastewater. The degraded
product in the ltrate and residue aer mineralization was
identied by FTIR and compared with the dye and KMnO4
peaks before and aer oxidation. The salinity of the recovered
water was determined through a Benchtop Conductivity/TDS
meter, Model Jenway 4510, before and aer the reaction.
Results and discussion. CR is a synthetic dye in which the p
to p* and n to p transitions are responsible for its color. When
20
Experimental
Materials and methods
Chemicals, materials, instruments and removal methods.
The sodium salt of benzidinediazo-bis-1-naphthylamine-4-
sulfonic acid referred to as Congo red (CR) belongs to the
class azo and is used to dye cotton fabrics, as the acid-base
indicator dye, and as a synthetic medicine dye. CR dye was
purchased from the local dye dupatta center and used without
any additional purication. The structure and chemical formula
of CR are shown below in Fig. 1.
4
these transitions were affected by an oxidant (KMnO ), the color
of the dye disappeared. It was observed that the reaction was
valid in light as compared to that in dark, which was linked with
A stock solution of 0.001 M of CR was prepared using double
distilled water and diluted according to the requirement of the
experiment. A standard method was employed for the prepa-
the property of the oxidant (KMnO ) that it is light-sensitive.
4
The kinetics of the reaction
4
ration of aqueous solutions of KMnO , acids, organic and
The current investigation at various operational parameters
described the newly developed advanced catalytic oxidation
process (ACOP) for the oxidation of CR. The reaction was carried
4
out at various concentrations of the dye (CR), oxidant (KMnO ),
pH, and temperature, and diverse organic (naphthalene and
urea) and inorganic (NaCl and alum) additives. These additives
are commonly employed for dye xing for cellulose bers. The
rate of reaction at elevated concentrations of various additives
proved that it is cost-effective. The current ACOP covers the
following steps: (i) taking a dye solution and adding KMnO
activation of KMnO by adding H SO , (iii) adding TiO
4
, (ii)
as
Fig. 1 The chemical structure of Congo red.
4
2
4
2
This journal is © The Royal Society of Chemistry 2019
RSC Adv., 2019, 9, 37562–37572 | 37563
Azmat, Rafia
