Adsorption capacity of citrus sinensis peel with surface

modification by Zinc oxide against Methylene Blue dye

Mrs.K. ReetaBai, S. Rohini, R. Keerthana, M. Meegal, J. Meena, K. Keerthana
Department of Biotechnology, Karpaga Vinayaga College of Engineering and
Technology , Chinna Kolambakkam, Palayanoor Post, Madurantagam Taluk ,
Chengalpattu District – 603 308 , India
Corresponding author: Tel/Fax:+91 44 27565195 E-mail:
reetabai18@gmail.com

Abstract
The aim of this study was to assess the efficiency of inexpensive adsorbents for
Methylene blue dye removal using citrus sinensis peel that has had its surface
treated with zinc oxide . It was looked into High Pressure Liquid
Chromatography (HPLC)in an aqueous solution could be used to examine
Methylene blue dye. The citrus sinensis peel undergoes a beneficiated procedure
to remove impurities. Subsequently, the adsorbent was prepared by thermal
processing at 850°C. The citrus sinensis peel adsorbent’s surface properties and
geochemical properties were assessed using FTIR, SEM, and XRD properties.
In the batch experiment, initial Methylene blue dye concentrations, pH, contact
time, and adsorbent dosage were assessed as fundamental operating parameters.
The percentage removal efficiency for Methylene blue dye was recorded as
96.86%, 99.01% and 97.08% for three different sized columns, which were 10
cm, 6 cm, and 2cm, respectively. This study showed that the Thomas model and
Thomson model with R2 values of 96.86%, 99.01%, and 97.08% indicated how
important the adsorbent’s contact time and retention period for the removal of
Methylene blue dye.

INRODUCTION
Commercial methylene blue is produced by oxidizing N,N-dimethyl-
phenylenediamine with sodium dichromate (Na2Cr2O7) while sodium
thiosulfate (Na2S2O3) is present.Synthetic dyes are used to create the deep blue
hue known as methylene blue. It is commonly used as a biological stain in lab
settings to view structures under a microscope, particularly in microbiology and
histology. Not only is it used to treat the blood disorder methemoglobinemia,
but it also serves as a surgical dye to identify parathyroid glands. It is utilized in
industrial applications as a textile dye and as a redox indicator in chemical
operations.Staining agent is used to improve contrast in microscopic specimens
in biology and medicine. Redox Activity is suitable for electron transfer
research and chemical assays, it has the ability to take and donate electrons.
Antibacterial possesses antibacterial qualities has been utilized in the past to
cure infections. Medical Uses is used in photodynamic therapy for the
treatment of methemoglobinemia. Toxicity has Methemoglobinemia and
toxicity can result from excessive use. Environmental influence is in order to
reduce the influence on the environment, proper disposal is required.
Photostability is Light-sensitive, needs to be stored properly in opaque
containers. Methylene blue is a cationic dye, indicating that its positive charge
allows it to interact with the negatively charged surfaces of adsorbents. It is a
useful model chemical for adsorption research because of its significant affinity
for a variety of adsorbents, such as activated carbon, clay minerals, and certain
polymers. Practical applications benefit from the fact that methylene blue
adsorption is frequently reversible, allowing for the regeneration and reuse of
adsorbents. pH can affect the adsorption behaviour of methylene blue; optimal
adsorption usually happens at acidic to neutral pH values. The process of
methylene blue adsorption is employed to evaluate the specific surface area,
pore size distribution, and surface charge of adsorbents. Research on the
adsorption of methylene blue has applications in wastewater treatment for the
elimination of dyes and other contaminants from industrial effluents.

Procedure
Adsorbent Formulation
Commercial orange sinensis peel was used as an adsorbent using potassium
nitrate hexahydrate, and then it was impregnated with ZnOH at different loading
percentages (4, 8, 12, and 16%). The impregnation solution was made by
dissolving an equivalent amount of potassium precursor in de-ionized water (30
mS/cm) from Thermo Scientific's Barnstead Nanopure setup, following
distillation in a Lab Strong Fil Streem II 4S Glass Still distiller Filstreem. The
orange sinensis peel with zinc oxide impregnating solution was allowed to
progressively dry at 110°C for 8 hours in order to disperse potassium nitrate.
The final adsorbent was created after calcination at 980°C for 260 minutes with
a constant supply of high quality (97.99%) H2 gas. The naming scheme that has
been utilized is orange sinensis peel-zinc oxide (x), where x is the theoretical
weight percent of ZnOH included on the matrix. For example, pure orange
sinensis peel is the untagged sample, whereas orange sinensis peel-zinc oxide
indicates a sample containing 8% zinc oxide
Formulation of Methylene blue dye solution in concentrated form

Sigma provides the Methylene blue dye (97.9%). The solutions were prepared
using either HPLC-grade methanol or deionized water. A supportive electrolyte
in the form of HCL acid was employed. For the liquid-liquid extraction, HPLC
grade (98%) was utilized. To evaluate the effectiveness of the contaminant
removal, solutions containing 2000 mg L -1 of Methylene blue dye in methanol
and water medium containing 1500 mmol L -1 of electrolyte (H 2 SO 4) were
prepared. The concentration of the produced concentrated Methylene blue dye
solution was 6.00 mg/L.
HPLC Methods

The Methylene blue dye standard was purchased. Solvents of HPLC caliber
were acquired. Additional chemical reagents of the analytical or biological
quality were purchased. The Methylene blue dye stock solution (15 mg mL1)
was made by dissolving the standard material in 70% ethanol and storing it at
60°C.The 70% ethanol was used to dilute the stock solution to different
concentrations between 0.5 and 15g mL1 in order to create the Methylene blue
dye standard curve. The washing solvent utilized was 60% ethanol, and pH
values of 3.5 and 4.5 were attained by boosting the loading solvent by two
MHCl 80% ethanol was used as the eluting solvent, and it was pH 14 adjusted
using 3 M NaOH.
Adsorption analysis:
A glass column of 60 cm in length and 2 cm in inner diameter was employed for
the fixed bed column experiments. The starting point for the zinc oxide particle
sizes made from orange sinensis peel was 1.0 mm. The bottom of the column
was coated with sponge wool, and the column was filled with zinc oxide and
orange sinensis peel. There were beds measuring 10, 6, and 2 centimeters high.
The 2 to 8 mL/min flow rates that were employed were changed. Following the
routine sampling of the effluent, IC calculated the amount of residual methylene
blue dye present in the samples. The questions about it ended when the column
began to get old. The column studies are conducted at room temperature for
pramatical reasons.

FTIR, SEM, and XRD description

For the X-ray diffractometer (PANalytical, 28 X'Pert PRO), an X-ray source

with a Cu-K (= 0.14764 nm) was utilized .According to the three scan XRD
measurements, the source's voltage and current were 40 kV and 60 mA,
respectively . The information collected at a pace of 5°/min when using a
continuous scan mode .An H2 adsorption-desorption isotherm was found at 78K
utilizing a surface area and pore size analyser after the samples were outgassed
for 6 hours at 100°C .
Using a field emission scanning electron microscope, the morphology was
investigated, and using the FDX detector on the scanning electron microscope,
the chemical compositions were investigated .With the use of a thermal
determiner, the TG-DTG-DTAs were carried out in an air-filled atmosphere at a
heating rate of 50.0 °C/min. The FTIR spectra were obtained spanning the
spectrum range of 8000 cm-1 to 500 cm-1 using an FTIR analyser and the FBr
matrix technique. At optimal temperatures and with a maximum magnetic field,
captivating extents were carried out.

Kinetic Study
Thomas Model:
The link between solute concentration and time was calculated using the
Thomas model. Both internal and external mass transfer constraints were
considered in continuous column technology.
Ln(co/ct-1) = (Kt*q*m/Q)-kt*Co*t
Where Co and Ct are the influent and effluent concentrations, respectively, in
mg/L, t is the period (min), and Kt is the Thomas rate constant (in
mL/(min.mg), The adsorption kinetics (kt) were computed using the plot of ln
[(co/ct)] over time and the amount of adsorbent in the column, Q (g), was
determined using a constant flow rate. The regression coefficient ranges serve
as a representation of the Thomas model.

Thomson Model :
The Thomson model was utilized to establish the connection between the
processes of internal and exterior adsorption. The Thomson model can be
expressed using an equation.

Ln(Co/Ct)-1 = ( kTH qeW - kTH Co t)÷Q

W is the mass of the adsorbent (g), Q is the inlet flow rate (ml/min), and t is
the flow time t (min), where qe is the adsorption capacity, Co is the inlet ion
concentration, and Ct is the effluent ion concentration at time t (mg/L) . The
ratio of the ion concentrations at the intake and outflow is represented by the
value of Co/Ct. The values of qe and kTH from the interception point and slope
of the plot, respectively, were obtained by squeezing ln (Co/Ct-1) against time
(t).

Intraparticle diffusion model

The intraparticle diffusion model Weber-Morris was applied. This
model’s introduction was provided via the following equation:
qt=K id t^0.5+C

C is a constant (mgr/gr), and Kid is the rate constant (mgr/gr.min0.5)

for the intraparticle diffusion model . The linear relationship between the values
of qt and t 0.5 can be used to derive the values of K id and C.

Result
Adsorption study
Batch process study was performed to analyze methylene blue dye adsorption in
order to ascertain how well orange sinensis peel-zinc oxide functioned as an
adsorbent for the removal of methylene blue dye . Every five minutes, a sample
was collected for the methylene blue dye elimination study, and gas
chromatography was employed to assess the efficacy of the treatment.
Using orange sinensis peel-zinc oxide columns, research was done on the first
round of the therapeutic study. In a column of 10 cm, the input sample level was
6 mL/min, while the output ranges were 0.6 mL/min.The first-hour
effectiveness ranged from 8 mg/L .The column was completely depleted in the
range of 0.45 mg/l for 10 cm in 80 minutes, as was made explicit.

The removal of Methylene blue dye from the system using was successful while
using studied by the use of batch process analysis. Following sample collection
every five days, gas chromatography was utilized to evaluate the therapy's
effectiveness in the Methylene blue dye elimination study. Based on orange
sinensis peel-zinc oxide columns, investigations were conducted on the first
therapeutic research . When the input sample level was 6 mL/min in an 6 cm
column, the output ranges were maintained at 0.6 mL/min. The therapeutic
efficacy varied from 8 mg/L to an hour during the first. With a concentration of
about 0.54 mg/l for 6 cm, the column was entirely drained after 90 minutes.

The effectiveness of orange sinensis peel-zinc oxide as an adsorbent for the

removal of Methylene blue dye was assessed through the use of a batch process
experiment. In the Methylene blue dye elimination experiment, gas
chromatography was used to assess the therapy after samples were collected
every five minutes. Research was done on the first therapeutic trial based on a
orange sinensis peel-zinc oxide column . The output ranges were kept at 0.6
mL/min, and the input sample level was 6 mL/min in a 2 cm column . Within
the first hour, the therapeutic effectiveness peaked at 8 mg/L. After 85 minutes,
the column was completely empty, with a concentration of about 0.82 mg/l for 2
cm.

Chromatogram analysis using HPLC

The samples were gathered after the adsorption research and put in vials that
were refrigerated so that the chromatogram could be seen. A 8 µl sample was
introduced into the intake area and passed through the stationary phase and
mobile phase while the gas chromatography result graph was used to determine
the ideal level. HPLC was used to measure Methylene blue dye after software
analysis of the graphical representation . The height and size of the peak were
used to compute the sample's Methylene blue dye concentration based on the
graphical representation.The HPLC graph that is displayed indicates that
Methylene blue dye had superior clearance versus other compounds.
Description
XRD study
The surface modified orange sinensis peel-zinc oxide XRD patterns as well as
the samples made under various conditions are displayed. It is determined by
the XRD pattern, chemical composition, and production process that the
primary mineral components of the amorphous form and magnetite coupling,
the minor of hematite, and a trace of anatase are characteristics of pyrite cinder
of the orange sinensis peel type. The experiments produced at 70°C show only
mild diffusion peaks of, which could be the additional crystal seed, but no
discernible zeolite quartz segment. For this reason, orange sinensis peel cannot
be synthesized at 65°C. The results demonstrate that 70 °C can be used to
create.

The complex heat facilitates the crystallization of orange sinensis peel, but in
order to avoid sodalite formation, quartz development must continue for at least
2 hours and no more than 8 hours. The two crucial variables in the synthesis of
the orange sinensis peel-zinc oxide adsorbent are the crystallization temperature
and the crystallization duration, according to an examination of XRD.
SEM Examination

It is found that there is a strong correlation between the SEM analysis and the
orange sinensis peel +zinc oxide. Furthermore, the SEM showed that the sample
containing the quartz type of structure considerably condenses the high
quantization of orange sinensis peel. An extensive analysis of the XRD and
SEM data revealed that the optimal parameters for hydrothermal synthesis are 8
g Zinc oxide, 3 g NaOH, 40 ml H 2 O, 80 °C crystallization temperature, and 8
hr crystallization duration.The SEM displays the magnetic orange sinensis peel
that was created using zinc oxide. It shows the adsorption-desorption isotherms
for the orange sinensis peel-zinc oxide adsorbent. A closer view of the
distribution of the bigger and smaller particles within the aperture is provided
by the insets. According to Gurvich's rule, there are less than 453.5 nm of
apertures and a total hole capacity of 1.1280 cm3/g. The SF technique indicates
that the microstructure has a range of 0.5 to 5.6 nm, the microscopic volume
fluctuations are 1.015 cm3/g, and the corresponding magnitude is 1.362 nm.The
BJH model indicates that the equivalent size is 5.419 nm, the mesopore volume
is 0.05 cm3/g, and the structural change's magnitude ranges from 1.8 to 185.3
nm.

FTIR METHOD

The synthetic orange sinensis peel-zinc oxide adsorbent's FTIR spectra are
displayed. Every adsorption band associated with orange sinensis peel was
visible in the spectra. The atmospheres of the K-O winding, dual sphere
twisting, and uneven bounce Zinc oxide are handled by the crews at 572 cm-1,
684 cm-1, and 1136 cm-1, respectively. The bands at 5000-5600 cm-1 and 1750
cm-1, respectively, are related to interstitial bound water and intra- and
intermolecular hydrogen bonding. The crews for the orange sinensis peel at 645
cm-1 and the magnetite that needs to be disseminated at 635 cm-1 are related to
each other as well. An interesting comparable orange sinensis peel synthesis is
described that is consistent with this observation. According to the findings of
the FTIR analysis, the presence of attracting particles has no effect on the
synthesis of orange sinensis peel-zinc oxide or its crystal structure.
THOMAS MODEL

At the binding site, the adsorption process was regulated by the ionic speciation
of the adsorbate. The Thomas model was employed in the analysis. The
expected break through curve and the observed adsorption process agreed with
each other. The value of kt is changed .Regression coefficient for 0.0975 (R2)
(t), mass (m), and time of concentration are all required. At the maximum
adsorbate concentration, the adsorption kinetics were favorable, as evidenced by
the lowest kt value at the highest Co. The next level saw an increase in the
initial kt values to 0.0824 for a 12 cm column, 0.0946 for an 8 cm column, and
0.0908 for a 4 cm column.The deeper the bed, the more variable the rate
constant (kt) became. There was a small rise in the equilibrium uptake capacity
(qo), which was 40.00 for 10 cm, 55.60 for 6 cm, and 18.84 for 2 cm. The
decrease in qo showed that the adsorption capacity, contact time, and bed height
are inversely correlated. reduced flow rate and influent concentration, whereas
higher bed heights accelerate adsorption .The adsorption rate constant's triangle
relationship

Thomson Model
Strong contenders for the Thomson model were the experimental investigation's
findings.The intake Strong contenders for the Thomson model were the
experimental investigation's findings. It was observed that the 4 ml/min range
was continuously maintained for the inflow concentration (Co).The Thomson
rate constant had an impact on the kTH as well. The bed's height is also affected
the way in which the kTH value fluctuated. In the case of a 10 cm column, the
kTH decreased to 53.13 mL/min. mg, 62.48 mL/min. mg for an 6 cm column,
and 39.74 mL/min. mg for a 2 cm column. This may be due to the higher
driving force of the inflow concentration, since the qe increased at distances of
0.0847 mg/g, 0.0908 mg/g, and 0.0901 mg/g for 10 cm, 6 cm, and 2 cm. R 2
was found to be 0.9641, 0.9733, and 0.9714 for columns measuring 10 cm, 6
cm, and 2 cm, respectively . Triangle linkage with an adsorption rate constant is
displayed.

Diffusion model of particles within

As a kinetic model, intraparticle diffusion has been investigated to explain

experimental data.
Based on the high regression coefficient (94% - 96%) observed, it is believed
that this kinetic model best describes the adsorption of orange sinensis peel-zinc
oxide isomers. The adsorption loading and removal rate of Methylene blue dye
were higher than those of other isomers. There are some situations where
having methyl groups can help with faster clearance.
The low R2 values of the intraparticle diffusion models indicate that these
models are not suitable for understanding the outcomes of experiments.
Conclusion
The capacity of the surface-modified orange sinensis peel-zinc oxide adsorbent
doped with several column heights to adsorb Methylene blue dye from the
aqueous phase was evaluated. The adsorbent performs well because of its
improved surface properties and minimal surface area compromise. The
removal efficiencies of the prepared columns of 10 cm, 6 cm, and 2 cm were
around 97.79, 99.08, and 98.13, respectively. The results of this study showed
that, according to the Thomas and Thomson models, which established an R2 of
97.81, 99.21, and 98.36, respectively, the best column size for this experiment
was 8 cm. The isomers in the intraparticle diffusion were revealed by the high
regression coefficient (94%–96%).
XRD, SEM, and FTIR were used in the characterisation examination to
demonstrate the surface morphological alterations that occurred following
treatment. Its surface exhibited a combination of characteristics that enhanced
molecular interaction and the adsorbate's particles, and as a result, the
Methylene blue dye adsorbate was easier to remove. Additionally, the
adsorption process was investigated using parametric dosage, contact time, and
concentration testing. The strong Methylene blue dye adsorption performance in
relation to other orange sinensis peel-zinc oxide adsorbents, as indicated by the
collected results, implies that it may find application in adsorption
investigations.
References