β-Cyclodextrin modified chitosan and κ-carrageenan composites for acid fuchsin dye removal: mechanism insight and adsorption performance

Abstract

This study is aimed at developing a highly effective adsorbent by physically crosslinking chitosan (CH), kappa-carrageenan (KCG), and β-cyclodextrin (β-CD) for removing acid fuchsin (AF) dye from water. Various analytical techniques, such as PXRD, FTIR, FE-SEM, and EDS, were utilized to analyze the interactions and morphology of the crosslinked biosorbents. The adsorption performance of CH/KCG and CH/β-CD/KCG biosorbents was assessed under diverse reaction conditions. The adsorption capacity increased with agitation time, reaching equilibrium at 240 min for CH/β-CD/KCG and 300 min for CH/KCG. CH/β-CD/KCG demonstrated the highest adsorption capacity among the two adsorbents studied. The maximum adsorption efficiencies were found to be 9.979 mg/g for CH/KCG and 10.98 mg/g for CH/β-CD/KCG biosorbents under neutral pH and at 30 °C (optimum temperature). Comparing CH/KCG with CH/β-CD/KCG, a notable increase of approximately 13.6% in AF adsorption was observed. Kinetics revealed a pseudo-second-order mechanism, and isotherm models suggested monolayer adsorption following Langmuir isotherm. Thermodynamic analysis indicated a low temperature, spontaneous, and exothermic adsorption process. The activation energy values were calculated as 47.515 and 18.269 kJ/mol for CH/β-CD/KCG and CH/KCG, respectively, indicating physical interactions as the driving force for adsorption. Acid fuchsin adsorption was primarily attributed to physical interactions and hydrogen bonding, facilitated by polymer and inclusion formation mediated by β-CD through host–guest interactions. Furthermore, the biosorbents showed remarkable reusability after three cycles of adsorption and desorption, indicating their promising potential as natural biosorbents for the removal of cationic dyes.

Graphical Abstract

Full text

Vol.:(0123456789)
Biomass Conversion and Biorefinery
https://doi.org/10.1007/s13399-024-05799-5
ORIGINAL ARTICLE
β‑Cyclodextrin modified chitosan andκ‑carrageenan composites
foracid fuchsin dye removal: mechanism insight andadsorption
performance
VasudhaVaid1· Khushbu2· MadhumitaSharma1· Parul1· NehaMaurya1· RajeevJindal1
Received: 28 March 2024 / Revised: 22 May 2024 / Accepted: 30 May 2024
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024
Abstract
This study is aimed at developing a highly effective adsorbent by physically crosslinking chitosan (CH), kappa-carrageenan
(KCG), and β-cyclodextrin (β-CD) for removing acid fuchsin (AF) dye from water. Various analytical techniques, such as
PXRD, FTIR, FE-SEM, and EDS, were utilized to analyze the interactions and morphology of the crosslinked biosorbents.
The adsorption performance of CH/KCG and CH/β-CD/KCG biosorbents was assessed under diverse reaction conditions.
The adsorption capacity increased with agitation time, reaching equilibrium at 240min for CH/β-CD/KCG and 300min for
CH/KCG. CH/β-CD/KCG demonstrated the highest adsorption capacity among the two adsorbents studied. The maximum
adsorption efficiencies were found to be 9.979mg/g for CH/KCG and 10.98mg/g for CH/β-CD/KCG biosorbents under neu-
tral pH and at 30°C (optimum temperature). Comparing CH/KCG with CH/β-CD/KCG, a notable increase of approximately
13.6% in AF adsorption was observed. Kinetics revealed a pseudo-second-order mechanism, and isotherm models suggested
monolayer adsorption following Langmuir isotherm. Thermodynamic analysis indicated a low temperature, spontaneous, and
exothermic adsorption process. The activation energy values were calculated as 47.515 and 18.269kJ/mol for CH/β-CD/KCG
and CH/KCG, respectively, indicating physical interactions as the driving force for adsorption. Acid fuchsin adsorption was
primarily attributed to physical interactions and hydrogen bonding, facilitated by polymer and inclusion formation mediated
by β-CD through host–guest interactions. Furthermore, the biosorbents showed remarkable reusability after three cycles
of adsorption and desorption, indicating their promising potential as natural biosorbents for the removal of cationic dyes.
Keywords Chitosan· β-Cyclodextrin· Kappa-carrageenan· Biosorbents· Acid fuchsin· Adsorption· Host–guest
interactions· Reusability
Abbreviations
CH Chitosan
AF Acid fuchsin
β-CD Beta-cyclodextrin
KCG Kappa-carrageenan
1 Introduction
Numerous sectors, including paper, textiles, dyestuffs, and
plastics, utilize significant amounts of water and incorpo-
rate chemicals and dyes in their manufacturing processes to
impart color to their products. Consequently, these industries
produce a considerable quantity of wastewater that is pol-
luted [1, 2]. Water bodies experience a reduction in light
penetration and photosynthesis due to the presence of dyes.
These dyes degrade and produce harmful substances, includ-
ing carcinogens [3]. The diminished photosynthetic activity
of organisms within aquatic ecosystems has consequences
that include a decrease in dissolved oxygen (DO) levels.
This decline in DO quality leads to an increase in biological
oxygen demand (BOD), chemical oxygen demand (COD),
total suspended solids (TSS), and other indicators that affect
water quality [4]. As pollution levels continue to rise and the
global demand for freshwater doubles every 20years, it is
* Khushbu
mail2khushbuyadav@gmail.com
1 Polymer andNanomaterial Lab, Department ofChemistry,
Dr. B R Ambedkar National Institute ofTechnology,
Jalandhar-144008, Punjab, India
2 Department ofTextile andFiber Engineering, Indian Institute
ofTechnology, NewDelhi-110016, India

Biomass Conversion and Biorefinery
projected that by the year 2020, the percentage of the popu-
lation experiencing chemical allergies will reach 60% [5].
In the context of waste treatment, the removal of dyes
holds significant importance, often surpassing the removal
of other organic substances. This is since even small quanti-
ties of dyes (less than 1ppm) are easily noticeable and have
a substantial impact on the overall water environment [6]. A
significant portion exceeding 85% of undesired substances
can be eliminated through the implementation of different
methods for treating effluent [7]. Dyes are typically catego-
rized into two primary groups: natural and synthetic dyes.
Synthetic dyes can be further divided into anionic and cati-
onic dyes, with cationic dyes being notably more detrimental
than their anionic counterparts [8]. Acid fuchsin (AF), a
commonly used cationic dye in various industrial processes
such as coloring textile materials and fabrics, wool, silk,
leather, and nylon [9], poses significant challenges due to
its persistence and potential adverse effects on ecosystems
and human health. It is also used as a corrosion inhibitor
and laboratory reagent [10]. Inhalation, ingestion, or skin
absorption of AF can pose potential harm, as it is known to
irritate mucous membranes, the upper respiratory tract, eyes,
and skin [11]. The escalating environmental concerns asso-
ciated with textile industry effluents containing synthetic
dyes necessitate the development of effective and sustainable
remediation strategies. These methods encompass a range of
techniques such as electrochemical oxidation, electro-coagu-
lation, electrochemical reduction, advanced oxidation, incin-
eration, photolysis, adsorption on activated carbons, sand or
carbon filtration, membrane filtration, catalytic/non-catalytic
oxidation, biological activated sludge, ion-exchange on res-
ins, and membrane bioreactors [12]. Due to their expensive
nature, challenges in disposal, and technical limitations, sev-
eral treatment methods for addressing dyes in pre-treated
effluents have not been extensively implemented on a large
scale. Consequently, there is a demand for the development
of novel strategies and decolorization methods that are both
efficient and environmentally friendly, while also being suit-
able for industrial applications.
Research findings indicate that adsorption proves to be a
highly efficient approach for the removal of pollutants from
wastewater, and it is extensively employed in industrial pro-
cesses due to its cost-effectiveness, straightforward design,
ease of operation, and ability to prevent secondary pollution
[13]. Biosorption, employing natural or modified biopoly-
mers as adsorbents, emerges as a promising approach for
dye removal owing to its cost-effectiveness, eco-friendliness,
and versatility. Researchers have tried a variety of methods
to create less expensive and more efficient adsorbents to
remove colors from wastewater [14, 15]. The biocompatible,
biodegradable, and non-toxic properties of natural polysac-
charides make them preferably more suitable for biosorbent
synthesis [16, 17]. Natural polysaccharides include agarose,
chitosan, alginate, fucoidan, carrageenan, cellulose, and
hyaluronic acid [18]. Chitosan (CH)-based biosorbents are
by far the most extensively studied material among those
suggested for water and wastewater treatment by biosorp-
tion. This is due to their ability to remove a wide range of
pollutants and simpler ways to synthesize them [19–22].
CH is a cationic polymer, and its biosorbents can be held
together either by physical interactions like hydrogen bond-
ing, electrostatic interactions, Vander Waal’s forces, or by
chemical crosslinking by covalent bonds [12, 23–27]. Nev-
ertheless, for the practical application of CH, there is a need
to develop methods for enhancing the adsorption capacity
of CH. In recent years κ-carrageenan (KCG), a naturally
occurring polymer, is gaining a lot of attention in adsorp-
tion. It is derived from red seaweeds and possesses several
advantageous properties such as being biodegradable, non-
toxic, biocompatible, renewable, and hydrophilic with sig-
nificant adsorption capacity towards cationic dyes due to the
presence of numerous functionalities (sulfate and hydroxyl
groups) [28, 29]. Despite its advantages, the use of KCG
is limited due to its low environmental stability and weak
gel strength. Consequently, enhancing the physicochemical
properties of KCG presents a challenging task when it comes
to its application as a bio-adsorbent. A potential solution to
enhance the adsorption capabilities and overall properties of
KCG is to blend it with other polymers. CH and KCG, abun-
dant biopolymers renowned for their biocompatibility and
adsorption capabilities, have garnered considerable interest
in biosorption applications. This approach allows for the
development of a novel adsorbent that exhibits significantly
improved adsorption capabilities and enhanced properties
[30]. The incorporation of β-cyclodextrin (β-CD) into CH
and KCG matrices offers enhanced adsorption efficiency
through the formation of inclusion complexes and improved
surface properties [31, 32].
β-Cyclodextrin (β-CD) is a macrocyclic oligosaccharide
composed of seven α-1,4-linked D-glucopyranose units,
featuring an internal hydrophobic cavity. This cavity allows
for the inclusion of a wide variety of guest molecules that
possess suitable size and nonpolar properties, forming stable
inclusion complexes. However, the application of β-CD in
formulations is limited due to its low aqueous solubility.
When β-CD is incorporated into the crosslinked network
of a hydrogel, the resulting β-CD-functionalized hydrogels
exhibit synergistic properties beneficial for treating pigment
wastewater. Specifically, the hydrophilic network structure
of the hydrogel enhances water solubility, while the hydro-
phobic cavity of β-CD improves the stability of inclusion
complexes during adsorption processes. Additionally, the
reactive hydroxyl (-OH) groups on the outer rim of β-CD
can be modified with various functional groups to further
impart specific properties to β-CD. Therefore, it is reason-
able to speculate that the unique properties and non-toxic

Biomass Conversion and Biorefinery
nature of β-CD, when combined with hydrogel properties,
make it an attractive and potentially effective option for the
simultaneous removal of various pollutants from water. Cur-
rently, β-cyclodextrin and hydrogels as individual adsor-
bents exhibit low dye removal rates. Hence, it is essential to
develop a new type of adsorbent that leverages the combined
advantages of β-CD and hydrogel, utilizing the synergy
between them [33, 34].
The novelty of this research lies in the modification
of biosorbents using β-CD, aimed at enhancing their dye
removal capacity. By incorporating β-CD through physi-
cal interactions, this study seeks to explore the potential of
CH/β-CD/KCG biosorbents for efficient dye removal. This
study is aimed at presenting a comprehensive investiga-
tion into the synthesis of a novel β-cyclodextrin-mediated
biosorbent based on CH and KCG for the efficient removal
of AF dye from aqueous solutions. To assess the efficacy
of the modified biosorbents, we employed kinetic models,
isotherms, and thermodynamic studies to evaluate the dye
adsorption process comprehensively. Our findings contrib-
ute to the advancement of biosorption strategies tailored
for the efficient removal of dyes, thus addressing envi-
ronmental concerns associated with industrial wastewater
contamination.
2 Experimental
2.1 Materials
CH (extracted from crab shells with a deacetylation degree
of 85%) was supplied by HI Media, India. KCG was pro-
cured from TM Media (Delhi). β-Cyclodextrin and analyti-
cal grade acetic acid were provided by Sigma Aldrich, India.
Deionized water was utilized throughout the experimental
work.
2.2 In‑air (IA) synthesis ofchitosan
andkappa‑carrageenan‑based biosorbent
2.2.1 CH/KCG (IA) biosorbent
Natural polysaccharides: CH and KCG were used to synthe-
size the biosorbent by electrostatic interactions. In a beaker
of 50mL, 0.2g of CH was dissolved in 0.1M acetic acid
(15mL) and stirred for 20min. In an adequate amount of
distilled water, 0.1g of KCG was dissolved. The two solu-
tions were then mixed thoroughly and stirred continuously
to form a uniform mixture. This mixture was transferred
into a Petri dish and placed in a hot air oven for 8h at 60°C
to permit the synthesis of biosorbent and removal of all the
solvents. After 8h, a dry film-like biosorbent was obtained
and washed with acetone to remove the unreacted material.
2.2.2 CH/β‑CD/KCG (IA) biosorbent
β-CD (0.05mol/L) was added to the homogenous mixture
of CH and KCG. The mixture was transferred into a Petri
dish and dried in the oven at 60°C for 8h to obtain a dry
film of biosorbent.
2.3 Characterization ofCH/KCG andCH/β‑CD/KCG
biosorbents
2.3.1 Fourier transform infrared (FTIR) spectroscopy
Powders of pure backbones, i.e., CH and KCG; β-CD, CH/
KCG, and CH/β-CD/KCG were used to form sample pal-
lets with KBr salt to scan from 400 to 4000 cm−1.
2.3.2 Powder X‑ray diffraction (PXRD)
XRD of CH, KCG, CH/KCG, and CH/β-CD/KCG biosor-
bents was obtained by scanning the samples at 2θ ranging
from 10 to 90° with the scanning speed of (2°/min).
2.3.3 Field emission scanning electronic microscopy
(FE‑SEM) andenergy dispersive spectroscopy (EDS)
Analysis of surface morphology and elemental composi-
tion of backbones, β-CD, and biosorbents was done using
FESEM and EDS.
2.4 Water uptake measurement ofbiosorbents
The measurement of water uptake by biosorbents was done
by keeping them in deionized water. After a specific inter-
val, the biosorbent was removed and weighed, with any
excess water on the surface of the synthesized biosorbent
being wiped off before weighing. This process was con-
tinued until the equilibrium was reached, and the biosorb-
ent was swelled to its maximum capacity. The swelling
percentage was calculated using the following formula.
where Ws denotes the weight of the swollen biosorbent, and
Wd denotes the weight of the dried biosorbent.
2.5 Acid fuchsin (AF) dye absorption studies
Model dye (AF) adsorption experiments were conducted
on the synthesized biosorbents under different conditions,
including variations in temperature, pH, dye concentra-
tion, and adsorbent dosage. The removal of AF dye from
(1)
P
S=
W
s
−W
d
Wd
×
100

Biomass Conversion and Biorefinery
solutions (aqueous) was analyzed as well as studied using
a UV–visible spectrophotometer (LABINDIA ANA-
LYTICAL UV 3092). The dye absorption capacity per
unit of adsorbent (qt) and percentage removal (% R) from
the aqueous medium was calculated using the following
equation:
where Co is the initial concentration (mg/L), Ce is the equi-
librium dye concentration (mg/L), V is the volume of solu-
tion (L), m is the adsorbent weight (g), and % R is the per-
centage dye removal.
(2)
q
e=
C
o
−C
e
m
×V
(3)
%
R=
C
o
−C
e
Co
×
100
2.6 Dye adsorption kinetics
The AF dye adsorption on both synthesized biosorbents was
studied using four basic kinetic models as Elovich model,
intraparticle diffusion, pseudo-first-order, and pseudo-sec-
ond-order [35, 36].
2.6.1 Pseudo‑first‑order model
The equation for pseudo first order is given by
where qe denotes the amount of adsorbed dye (mg g−1) at
equilibrium, qt is the amount of adsorbed dye (mg g−1) at a
given time, lnqe is intercepted, and k is represented as equi-
librium rate constant (min−1).
(4)
ln(qe−qt)=lnqe−k1t
Scheme1 Systematic pro-
cess to synthesize chitosan,
kappa-carrageenan, and
β-cyclodextrin-based biosorbent

Biomass Conversion and Biorefinery
2.6.2 Pseudo‑second‑order model
According to this model, the dye adsorption process’ rate-
determining step is affected by the chemisorption process.
The pseudo-second-order equation is as follows.
where qe represents the amount of adsorbed dye (mg g−1)
at equilibrium, qt is the amount of adsorbed dye (mg g−1) at
a specific time, and k2 is the rate constant for second order
(mg (g min)−1).
(5)
t
qt
=
1
k2q2
e
+
1
q
e
t
2.6.3 Intraparticle diffusion model
In addition to adsorption at the adsorbents’ outer surfaces,
intraparticle diffusion from the exterior layer into the mate-
rial’s pores is also feasible. This model’s equation is as follows.
Here, ki is the intraparticle diffusion rate constant, and C
is the constant that denotes the resistivity for the layer. The
value of ki was calculated by plotting qt against t1/2.
(6)
qt
=k
i
t
1∕2
+C
Fig. 1 a–e Optimization graph
for maximum percentage
swelling a reaction temperature
(40–80°C), b reaction time
(5–10h), c backbone ratio (CH:
KCG; 4:1–1:4), d amount of
β-CD (0.03–0.05mol/L) in
biosorbent, e amount of solvent
(13–21mL), and e pH of the
solution (2–11)

Biomass Conversion and Biorefinery
2.6.4 Elovich model
The equation of the simple Elovich model is generally as
follows.
where α and β are the constants. The graph between qt and
lnt is plotted and the intercept gives the value of 1/β ln (αβ),
and the slope gives the value of 1/β.
(7)
q
t=
1
𝛽
ln(𝛼𝛽)+
1
𝛽
ln
t
2.7 Dye adsorption isotherms
Adsorption isotherms were used to analyze the mechanisms for
the adsorption of dye on both biosorbent surfaces. With the use of
four fundamental isotherm models Langmuir, Freundlich, Tem-
kin, and Elovich isotherm, the adsorption values were studied.
2.7.1 Langmuir isotherm
This isotherm is suitable for the monolayer adsorption of adsorb-
ate (dye) molecules on the adsorbent (biosorbent) surface [37].
Table 1 Optimization of different reaction parameters in the synthesis of CH/KCG biosorbent
Values in bold represents the most optimized condition having the maximum percentage swelling
Sr. No Ratio of backbones
(CH: KCG; 2:1)
Amount of solvent (mL)
(acetic acid: water; 13:2)
Temperature
(60°C)
Time (8h) pH (5) β-CD
(0.05mol/L)
Swelling (%)
1 4:1 13:2 60 8 5 0.05 787
2 3:1 13:2 60 8 5 0.05 833
32:1 13:2 60 8 5 0.05 1055
4 1:1 13:2 60 8 5 0.05 581
5 1:2 13:2 60 8 5 0.05 347
6 1:3 13:2 60 8 5 0.05 373
7 1:4 13:2 60 8 5 0.05 239
8 5:1 13:2 60 8 5 0.05 Gel not formed
9 2:1 12:1 60 8 5 0.05 1053
10 2:1 13:2 60 8 5 0.05 2220
11 2:1 14:3 60 8 5 0.05 1273
12 2:1 15:4 60 8 5 0.05 943
13 2:1 16:5 60 8 5 0.05 740
14 2:1 17:6 60 8 5 0.05 631
15 2:1 13:2 40 8 5 0.05 801
16 2:1 13:2 50 8 5 0.05 913
17 2:1 13:2 60 8 5 0.05 1553
18 2:1 13:2 70 8 5 0.05 928
19 2:1 13:2 80 8 5 0.05 831
20 2:1 13:2 60 5 5 0.05 885
21 2:1 13:2 60 6 5 0.05 907
22 2:1 13:2 60 7 5 0.05 935
23 2:1 13:2 60 85 0.05 1231
24 2:1 13:2 60 9 5 0.05 996
25 2:1 13:2 60 10 5 0.05 856
26 2:1 13:2 60 8 2 0.05 3824
27 2:1 13:2 60 8 50.05 5930
28 2:1 13:2 60 8 7 0.05 2447
29 2:1 13:2 60 8 9 0.05 122
30 2:1 13:2 60 8 11 0.05 782
31 2:1 13:2 60 8 5 0.03 1321
32 2:1 13:2 60 8 5 0.04 1464
33 2:1 13:2 60 8 5 0.05 1923
34 2:1 13:2 60 8 5 0.06 1509
35 2:1 13:2 60 8 5 0.07 1453

Biomass Conversion and Biorefinery
Fig. 2 a Combined FTIR spectra of CH, KCG, CH/KCG, and CH/β-CD/KCG. b Combined XRD pattern of CH, KCG, CH/KCG, and CH/β-CD/
KCG. c FESEM images of CH, KCG, CH/KCG, and CH/β-CD/KCG. d EDS spectra of CH, KCG, CH/KCG, and CH/β-CD/KCG

Biomass Conversion and Biorefinery
This isotherm implies uniform adsorption and a lack of inter-
action between adsorbed species and is given by the equation.
(8)
C
e
qe
=
1
q
m
K
L
+
Ce
q
m
Here, qe is the dye adsorbed at equilibrium, Ce denotes the
dye’s eq. concentration (in mg L−1), b denotes the Langmuir
constant, and qm denotes monolayer capacity. The intercept
and slope of a plot of Ce/qe vs. Ce were used to derive the
values of b and qm.
Fig. 3 a–e: a Effect of a concentration of dye (10–50ppm), b pH (2–11), c temperature (20–60°C), d adsorbent dose (0.05–0.3g), and e contact
time (60–300min) on percentage removal of acid fuchsin dye

Biomass Conversion and Biorefinery
2.7.2 Freundlich isotherm
A multilayered dye adsorption/distribution onto an uneven
surface with an extremely high number of active sites is
assumed in the Freundlich model, an experimental equation
[38]. Calculated using the equation below:
Here, kf is the adsorption capacity (mg/g), and 1/n is the
heterogenicity factor. The 1/n value indicates whether the
model is significant or not. The isotherm is unfavorable
when the value of 1/n exceeds 1. The isotherm is revers-
ible when the value of 1/n is equal to zero, and it would be
favorable when the value of 1/n is between zero and one
(0 < 1/n < 1). The plot of ln Ce vs. lnqe and the slope (1/n)
and intercept (lnkf) of the curve were calculated.
2.7.3 Temkin isotherm
Heterogeneous surface energy systems frequently make use
of the Temkin isotherm. The Temkin isotherm model equa-
tion is as follows.
where qe represents the equilibrium amount of dye adsorbed,
Kt represents the Temkin constant, and b represents the con-
stant corresponding to the sorption heat (J/mol). The process
is exothermic when the b constant’s value is positive and
endothermic when the value of b is negative.
2.7.4 Elovich isotherm
This model is based on the kinetic premise that, in a mul-
tilayer, active sites increase with adsorption. The Elovich
equation is represented by
where Ce is the concentration at equilibrium, qm is the
maximum absorption capacity, and qe is the quantity of dye
adsorbed at equilibrium.
3 Results anddiscussion
3.1 Formation ofCH/β‑CD/KCG biosorbent
The major processes that resulted in the biosorbent for-
mation were physical interactions between the oppositely
charged polymeric backbones. The NH3+ units of CH and
(9)
ln
qe=lnKF+
1
n
lnC
e
(10)
q
e=
RT
b
lnKT+
RT
b
lnC
e
(11)
ln
qe=lnqm−B(RT ln
(
1+1
C
e)
)
2
-OSO3− units of KCG are the major groups taking part in
holding the polymers together. The positively charged amine
groups on chitosan (CH) and negatively charged sulfate
groups on k-carrageenan (KCG) result in strong electro-
static interactions as illustrated in Scheme1. There is sig-
nificant hydrogen bonding between hydroxyl (OH) groups
of both the polymeric backbones causing network formation
via physical crosslinking. Similar electrostatic interactions
between the charged groups and hydrogen bonding between
the hydrophilic groups of CH and KCG result in the biosorb-
ent. The existence of multiple hydroxyl groups either on the
interior or exterior β-CD is responsible for incorporation in
the polymeric network of CH and KCG by physical inter-
actions, i.e., H-bonding, van der Waals forces. Scheme1
illustrates a simple physical crosslinking of CH/β-CD/KCG
biosorbent. The biosorbents were characterized according to
commonly used techniques.
3.2 Swelling andoptimization studies
ofsynthesized biosorbent
The swelling capacity of the synthesized CH/KCG biosorb-
ent was found to be 2220%. The incorporation of β-CD
resulted in a significant increase in the swelling capacity.
The percentage of the most optimized networks increased
when β-CD was incorporated. The even distribution of β-CD
within the polymer network likely played a role in increasing
the degree of swelling by enhancing surface roughness and
engaging in electrostatic interactions. The parameters opti-
mized were reaction time, pH, temperature, ratio of back-
bones, amount of solvent, and β-CD as shown in Fig.1a–e.
The maximum swelling was observed to be 5930% at pH 5
which shows that the synthesized biosorbent was pH-respon-
sive (Table1).
3.3 Characterization
3.3.1 Fourier transform infrared spectroscopy (FTIR)
The FTIR spectra of CH, KCG, CH/KCG, and CH/β-CD/
KCG are shown in Fig.2a. The FTIR graph of KCG pos-
sesses characteristic peaks at 1243 cm−1 and 844 cm−1 cor-
responding to the sulfate ester group, O = S = O, and C-O-S
axial secondary sulfate (O-SO3−), respectively. The signal
at 3415 cm−1 belongs to -OH stretch, 1037 cm−1 to gly-
cosidic linkage, 2971 cm−1 to C-H stretch of alkane, and
920 cm−1 to C–O–C linkage. The FTIR spectrum of chitosan
shows a characteristic peak at 3389 cm−1 at N–H stretch
or O–H stretch, 1653 cm−1 amide I, 1539 cm−1 amide II,
1150 cm−1 amide III, and 1026 cm−1 of glycosidic link-
age. In the IR spectrum of CH/KCG biosorbent, the char-
acteristic peaks of CH and KCG shifted to 1543 cm−1 and
1237 cm−1, respectively, with decreased intensity suggesting

Biomass Conversion and Biorefinery

Biomass Conversion and Biorefinery
the electrostatic interactions present between both groups.
As a consequence of interaction, the O–H stretch intensity
of the biosorbent decreases relative to pure backbones, and
it appeared at 3338 cm−1. In the FTIR graph of CH/β-CD/
KCG biosorbent, the characteristic peak of β-CD appeared
at 1153 cm−1 and 1029 cm−1 attributed to an asymmetric
and symmetric stretch of C–O–C which revealed the pres-
ence of β-cyclodextrin in biosorbent. The peak at 3370 cm−1
corresponds to the -OH stretch. The characteristic peaks of
KCG and chitosan appeared in the IR graph of the CH/KCG
biosorbent without the formation of any new peak, which
affirms the physical interactions between KCG and CH.
3.3.2 Powder X‑ray diffraction (PXRD)
The PXRD graphs of CH, KCG, CH/KCG, and CH/β-CD/
KCG are shown in Fig.2b. Chitosan gives distinct peaks at
2θ corresponding to 19.58°. In the case of KCG, the sig-
nal appears at 2θ equal to 21.3°. The XRD pattern of the
biosorbent showed a weak and broad peak, and no sharp
crystal peak was observed. The evident broadening of the
peak at 2θ of 20.73° with a decrease in intensity in the XRD
pattern of synthesized CH/KCG biosorbent indicated its
amorphous nature/since both of the backbones were amor-
phous. The decrease in biosorbent crystallinity in CH/β-CD/
KCG indicates that ionic interactions between CH and KCG
improved its compatibility.
3.3.3 FESEM andEDS
The FESEM and EDS images are shown in Fig.2c, d.
One of the most significant factors affecting the adsorption
of dye is the surface morphology of the biosorbent. Pure
CH has a semi-crystalline structure which is confirmed
by the fringes present in its FESEM image (Fig.2c). SEM
images explained that pure KCG contains smooth, nonpo-
rous surface morphology and compliments its amorphous
nature. The synthesized CH/KCG biosorbent has a more
rough, porous, and heterogeneous surface morphology.
The effect of β-cyclodextrin loading on the surface of the
CH and KCG network was revealed by FESEM. In addi-
tion to β-CD in the biosorbent, there is not much change
in the morphology of the biosorbent, but it enhanced the
irregular structure of the biosorbent. The swelling capac-
ity and adsorption capacity of synthesized CH/β-CD/KCG
biosorbent increased as the irregularity of the network
surface increased. The synthesized biosorbents possess a
porous structure encompassing diverse pore sizes. These
pores’ size plays a vital role in the swelling phenomenon
and enables the efficient diffusion of dyes within the inter-
nal regions of the biosorbent. The presence of pores offers
a multitude of active sites and a significantly large surface
area, which are accountable for these effects.
EDS was analyzed to detect the presence of elements
in the samples and the biosorbents. The EDS of pure CH
showed the presence of C, O, and N. In KCG, the elements
of C, O, and S can be confirmed as shown in Fig.2d.
3.4 Optimization parameters
To get the best dye removal, several parameters are varied,
including the initial dye concentration, pH, temperature, and
adsorbent amount for both CH/KCG and CH/β-CD/KCG
biosorbents.
3.4.1 Effect ofinitial concentration ofdye
The initial concentration of dye was varied from 10 to
50ppm to evaluate the amount of dye removed from the aq.
solution. When the dye concentration is increased, the per-
centage of dye elimination also increases. For AF, maximum
adsorption was obtained at 50ppm concentration when the
amount of biosorbent present in the solution was 0.2g. For
both synthesized CH/KCG and CH/KCG/βCD biosorbents,
50ppm concentration gave maximum percentage removal
(Fig.3a). This percentage is attainable because the solution
contains enough dye ions for the relevant surface available.
3.4.2 Effect ofpH ofaqueous medium
The solid/liquid interface’s pH impacts the adsorbent’s
surface properties as well as the chemistry of the adsorb-
ate. The pH of aq. the solution, ranging from 2 to 13,
was adjusted to observe how it affected the results of dye
adsorption as shown in Fig.3b. It was observed that maxi-
mum dye removal by the formed biosorbents occurred at
neutral pH. When the pH is acidic, the number of cations
on the biosorbent surface increases, and the efficacy of
adsorption decreases as repulsive forces between the posi-
tive dye molecules and the biosorbent surface increase. At
high pH, the amount of OH− ions increases, causing the
screening effect to become dominant and adsorption to
considerably decrease.
3.4.3 Effect oftemperature
The impact of temperature on the adsorption of dye was
investigated by changing the temperature from 20 to 70°C
Fig. 4 a–d Plots of kinetic models for the adsorption of AF dye on
the CH/KCG biosorbent: a pseudo-first-order, b pseudo-second-
order, c intraparticle diffusion, and d Elovich model; e–h plots of
kinetic models for the adsorption of AF dye on the CH/β-CD/KCG
biosorbent: e pseudo-first-order, f pseudo-second-order, g intraparti-
cle diffusion, and h Elovich model
◂

Biomass Conversion and Biorefinery
(Fig.3c). The highest percentage of dye clearance was
obtained at room temperature, i.e., 30°C. At higher tem-
peratures, the gel started breaking apart after some time and
proper adsorption of dye could not take place. It could be
possible because increased temperature disrupts electrostatic
interactions present in the gel.
3.4.4 Effect ofdose ofadsorbent
The adsorbent dose was changed between 0.05 and 0.25g
to investigate the effect on the elimination of AF dye
from solutions in Fig.3d. It was observed that increas-
ing the amount of adsorbent dosage enhances the percent-
age of dye elimination. It is because the surface area has
increased, thus increasing the fraction of active adsorption
sites for dye removal. At 0.3g maximum removal of dye
from the aq., the solution was obtained.
3.4.5 Effect ofcontact time
Figure3e depicts the times required to achieve equilibrium
for the acid fuchsin dye adsorption process on the surface
of each synthesized biosorbent. According to the experi-
mental data, 60% dye-ion removal was accomplished
after 70min for CH/β-CD/KCG biosorbent, while 60%
dye-ion removal was reached after 120min for CH/KCG
biosorbent. It was discovered that dye adsorption increased
with agitation time and reached equilibrium at 240min
for CH/β-CD/KCG biosorbent and 300min for CH/KCG
biosorbent. The dye’s adsorption capability increased
in the following order: CH/KCG < CH/β-CD/KCG. For
CH/β-CD/KCG, acid fuchsin dye elimination is relatively
high. This is due to the presence of β-CD molecules in the
adsorbent, which increases adsorption by forming inclu-
sion complexes (host–guest interactions).
3.5 Adsorption kinetics
Adsorption kinetics is important since it influences the
efficiency of the process. The adsorption rate of cati-
onic dyes is mainly determined by the physicochemical
properties of the adsorbent as well as the dye molecule
diffusion mechanism. The mechanism of AF dye adsorp-
tion on both synthesized biosorbents was studied using
Elovich models, intraparticle diffusion, pseudo-first-order,
and pseudo-second-order. The correlation coefficient (R2)
explains whether the procedure is favorable. The greater
the R2 value, the more significant is the model. For both
biosorbents, R2 was evident for the pseudo-second-order
model to be more significant than the Elovich, intraparticle
diffusion, and pseudo-first-order models (Fig.4a–h). By
forming the graph of ln (qe − qt) v/s t, k1 (min−1), and R2
values for pseudo-first-order were computed (Fig.4a). The
graph of t/qt v/s t gave the results of k2 (g/mg/min) and R2
for pseudo-second-order (Fig.4b). By plotting the graph
between qt and lnt, the values of α (mg/g/min), β (g/mg),
and R2 for the Elovich model were derived. The values of
all the constants are mentioned in Table2.
Table 2 Kinetic constants for adsorption of AF dye on CH/KCG and CH/β-CD/KCG biosorbents
S. No Kinetic model Kinetic parameter CH/β-CD/KCG biosorbent CH /KCG biosorbent
Acid fuchsin (ppm) Acid fuchsin (ppm)
10 20 30 40 50 10 20 30 40 50
1Pseudo-first-order k1 (min−1)0.012 0.018 0.012 0.014 0.013 0.011 0.015 0.012 0.017 0.021
qecal (mg/g) 0.772 1.002 3.328 6.978 10.43 0.921 1.543 3.412 5.989 9.598
qeexp (mg/g) 0.969 1.279 3.631 7.209 10.98 0.953 1.861 3.711 6.227 9.979
R20.867 0.909 0.923 0.921 0.951 0.939 0.864 0.963 0.964 0.931
2Pseudo-second-order k2 × 103 (mg/g min) 0.067 0.098 0.132 0.236 0.327 0.041 0.053 0.095 0.117 0.213
qecal (mg/g) 0.942 1.252 3.608 7.196 10.96 0.947 1.843 3.699 6.198 9.958
qeexp (mg/g) 0.969 1.278 3.631 7.209 10.98 0.953 1.861 3.711 6.227 9.979
R20.992 0.993 0.994 0.991 0.995 0.993 0.992 0.992 0.996 0.995
3Intraparticle diffusion ki (mg/gmin1/2)12.01 20.32 31.18 39.58 56.37 5.98 13.32 24.67 31.88 46.67
C1076 880.4 437.8 751.2 921.3 1246 938.5 664.4 835.3 772.9
R20.971 0.923 0.957 0.979 0.955 0.947 0.911 0.928 0.914 0.951
4Elovich model α (mg g−1min−1)5.59 343.8 21.20 78.96 188.7 1.62 20.06 16.57 74.21 166.1
β (mg g−1min−1)0.013 0.012 0.003 0.002 0.001 0.012 0.007 0.003 0.002 0.002
R20.885 0.898 0.899 0.908 0.913 0.895 0.896 0.908 0.890 0.913

Biomass Conversion and Biorefinery
3.6 Adsorption isotherm
Adsorption isotherms were used to analyze the mechanisms
for the adsorption of dye on both biosorbent surfaces. In all
experiments, 0.2g of synthesized adsorbents was dipped in
50mL of different concentrations of dye solutions. After a
fixed interval of time, the concentration (mg/L) was noted to
calculate the equilibrium concentration (qe, mg/L) of dye. To
determine the significant isotherm, four models were stud-
ied, namely, Langmuir, Freundlich, Elovich, and Temkin (in
Fig.5a–d). The values of all the constants and correlation
coefficients are mentioned in Table3. The highest value of
R2 corresponds to Langmuir isotherm for both CH/KCG and
CH/β-CD/KCG biosorbents, as evident from Table3. This
indicates that the Langmuir isotherm model is the most sig-
nificant. It signifies that the adsorption process is monolayer
in nature over the surface of both biosorbents.
3.7 Activation energy andthermodynamic
parameters
3.7.1 Activation energy
The Arrhenius equation can be used to determine activation
energy. The relationship between temperature and the kinetic
rate constant is given by this equation. The equation is as
follows.
where Ea is the activation energy, T denotes the tempera-
ture, R is the gas constant, and k2 is the pseudo-second-order
rate constant. The graph of lnk2 vs 1/T produces the values
of ko and Ea as shown in Fig.5e. The slope of the graph
provides the value of Ea, and ko is provided by the inter-
cept. The value of activation energy was calculated to be
47.515 and 18.269kJ/mol for CH/β-CD/KCG and CH/KCG,
respectively. The activation energy value indicated whether
the adsorption was physical or chemical. Adsorption is
described as physical if the value of Ea is low (0–88kJ/mol),
and chemical if the value of Ea is large (88–400kJ/mol). So,
the adsorption of dye is physical in nature as indicated by
low values.
3.7.2 Thermodynamic parameters
The Eyring equation was used to analyze the thermodynamic
parameters of entropy (So), enthalpy (Ho), and Gibbs free
energy (Go).
(12)
ln
k2=lnkO−
E
a
RT
where kb and h are Boltzmann (1.38 × 10–23J/mol/K) and
Planck’s constants (6.62 × 10–34J/s), respectively. The
graph’s value for ∆Ho and ∆So was determined by plotting it
against ln (k2/T) and 1/T (Fig.5f). The value of
[
ln
k
b
h
+ΔS0
]
is determined by intercept, and the slope gives the value of
∆Ho. The value of ΔHº and ΔSº was found to be − 251.48kJ/
mol and 23.76kJ/mol/K, respectively, for CH/ βCD/KCG
and − 188.85 kJ/mol and 14.32 kJ/mol/K for CH/KCG
biosorbents as mentioned in Table4. The relation between
Gibbs free energy, entropy, and enthalpy can be given by
Eq.(14).
By putting the values of T, ΔHº, and ΔSº in the above
equation, the values of Gibbs free energy can be calculated.
The negative value of enthalpy signifies that the adsorption
reactions are exothermic in nature. The positive values of
entropy and negative values of ΔGº prove the spontaneity
of the reactions (Table4).
3.8 Adsorption mechanism
According to the isotherm and kinetic findings, adsorption
is a physicochemical process with a variety of interactions
between AF dye and the synthesized biosorbents. Physical
forces like electrostatic interactions and hydrogen bonding
are responsible for the adsorption of dye in the synthesized
biosorbent as illustrated in Scheme2. According to the
abovementioned outcomes, CH/β-CD/KCG has a higher
capacity (93.11%) for AF dye adsorption than CH/KCG
(86%) biosorbent. CH/KCG biosorbent retains dye only
by electrostatic interactions and hydrogen bonding result-
ing in significantly lesser adsorption than β-CD-containing
biosorbent. The presence of β-CD ensures the host–guest
type of interactions between the CH/β-CD/KCG biosorbent
and the dye molecules and thus results in higher adsorption.
Electrostatic interactions occur between the positive amine
group of dye and the negative sulfate group present in the
KCG backbone of the biosorbent.
3.9 Reusability ofCH/KCG andCH/β‑CD/KCG
To assess the potential for practical application in dye
removal from wastewater, the reusability of CH/β-CD/KCG
and CH/KCG biosorbents was investigated through repeated
adsorption and desorption studies. Over three cycles, batch
mode experiments were conducted for the adsorption and
(13)
ln
k
2
T
=
[
ln
k
b
h
+ΔS0
R]
−ΔH0
RT
(14)
ΔGo=ΔHo−TΔSo

Biomass Conversion and Biorefinery

Biomass Conversion and Biorefinery
desorption evaluation of acid fuchsin (AF). In each cycle,
0.2g of dried gel was immersed in a solution containing AF
(50ppm, 50mL) for a period of 240min to ensure complete
adsorption. Subsequently, desorption was carried out over
the course of 240min using a 0.03M NaOH solution, fol-
lowed by rinsing with distilled water multiple times. The
efficiency of dye removal was observed to decrease from
93 to 80% in the second cycle and to 65% in the third cycle
for CH/β-CD/KCG, while for CH/KCG, the percentage
removal decreased from 86 to 72% in the second cycle and
to 59.5% in the third cycle as shown in F. Additionally, the
time required for maximum dye removal increased with suc-
cessive cycles. This decline in adsorption efficiency is likely
attributed to the saturation of adsorbent sites with adsorbate
molecules after each cycle, resulting in fewer accessible sites
for adsorption in subsequent cycles.
3.9.1 Comparison ofmaximum adsorption capacity
ofCH‑gl‑GG hydrogel foradsorption ofmalachite
green andauramine‑O ondifferent adsorbents
Table5 presents a comparison of the maximum adsorption
capacities of various materials as reported in recent litera-
ture, along with their optimal operating pH condition. How-
ever, a direct comparison is challenging due to the limited
research on the removal of acid fuchsin dye using different
adsorbents. So, the adsorption capacity of the synthesized
composite was compared with other absorbents already
reported in the literature to remove the other cationic dyes
as a model dye. The CH/β-CD/KCG adsorbent exhibited a
strong capability for removing cationic dyes. Although its
dye removal affinity is lower than that of the MCGMA-I
adsorbent, it surpasses several other adsorbents reported in
the literature, including Fe3O4/AC/CD/Alg, modified chi-
tosan composite, and β-CD crosslinked with CA, as demon-
strated by the comparative data in Table5. The significant
adsorption capacity of the CH/β-CD/KCG adsorbent indi-
cates its potential effectiveness for practical applications in
the removal of acid fuchsin dye from wastewater.
4 Conclusion
In conclusion, the synthesis of two biosorbents, CH/KCG
and CH/β-CD/KCG, using a hot air oven method, was suc-
cessfully achieved with optimized conditions including
reaction time, solvent composition, backbone ratio, β-CD
amount, temperature, and pH, leading to maximized swell-
ing capacity. Characterization techniques such as FTIR,
FESEM, EDS, and PXRD confirmed the successful synthe-
sis of polymers, revealing an amorphous nature and poros-
ity conducive to enhanced swelling. Comparative studies
demonstrated the superior removal efficiency of CH/β-CD/
KCG (95.6%) over CH/KCG (82%) in removing cationic
Fig. 5 a–d Isotherm models: a Langmuir isotherm, b Freundlich
isotherm, c Elovich isotherm, and d Temkin isotherm; e Arrhenius
plot, and f thermodynamic plot of adsorption of AF on CH/KCG and
CH/β-CD/KCG biosorbents; reusability plot of efficiency of g CH/
KCG and h CH/β-CD/KCG biosorbents for removal of AF
◂
Table 3 Isotherms constants for adsorption of AF dye on CH/KCG
and CH/β-CD/KCG biosorbents
S. no Isotherm model Kinetics
param-
eters
CH/β-CD/KCG CH/KCG
1 Langmuir isotherm K1355.3 327.1
qm429.1 488.4
R20.974 0.961
2 Freundlich isotherm KF0.201 0.169
n1.782 2.002
R20.807 0.898
3 Temkin isotherm KT0.008 0.007
b0.629 0.639
R20.919 0.937
4Elovich isotherm KE1.001 1.006
qm250.1 173.6
R20.904 0.932
Table 4 Thermodynamic parameters for the adsorption of acid fuchsin on CH/KCG and CH/β-CD/KCG biosorbents
Temperature
(K)
Biosorbents
CH/βCD/KCG CH/KCG
∆G00 (KJ/mole) ∆H0 (KJ/mole) ∆S0 (KJ/mole/K) ∆G0 (KJ/mole) ∆H0
(KJ/mole)
∆S0 (KJ/mole/K)
303 − 6677.3 − 251.48 21.20 − 4528.96 − 188.85 14.32
313 − 6889.3 − 4672.19
323 − 7101.4 − 4915.42
333 − 7313.5 − 4958.90

Biomass Conversion and Biorefinery
Scheme2 Schematic mechanism for AF dye adsorption on a CH/KCG and b CH/β-CD/KCG biosorbents
Table 5 Comparison of
adsorption capacity of
CH/β-CD/KCG adsorbents with
different adsorbents
Adsorbent Adsorbate pH Maximum adsorption
capacity (mg/g)
References
Modified chitosan composite MG 4 6.19 [39]
Fe3O4/AC/CD/Alg (polymer gel beads) MB 6 2.079 [40]
Fe3O4/AC/CD/Alg dry powder beads) MB 6 10.63
Activated carbon (commercial grade) MG 7 8.27 [41]
β-CD crosslinked with CA MB 7 5.5 [42]
CR 10.5
Activated carbon (laboratory grade) AO 7 7.608 [41]
Activated carbon (commercial grade) AO 7 1.431 [41]
EDTA crosslinked β-CD MB 6 0.262 (mmol/g) [43]
Safranine-O 0.169 (mmol/g)
CV 0.280 (mmol/g)
Magnetic alginate composite (MAlg) CV 7 0.113 (mmol/g) [44]
MCGMA-I RBBR 2 95.98 [45]
CH/β-CD/KCG AF 7 10.98 Present work
CH/KCG AF 7 9.979 Present work

Biomass Conversion and Biorefinery
dye (AF) from aqueous media, attributed to additional
host–guest interactions between β-CD and the dye molecule.
Kinetics and isotherm studies revealed second-order kinetics
and Langmuir isotherm, respectively, suggesting monolayer
adsorption. Thermodynamic analysis indicated a low tem-
perature, spontaneous, and exothermic adsorption process.
Furthermore, the biosorbents displayed promising reusabil-
ity across three cycles of adsorption and desorption, under-
scoring their potential as effective and sustainable materials
for environmental remediation applications.
Acknowledgements For the characterizations, the author is grateful to
IIC NIT Jalandhar and Material Research Centre Jaipur.
Author contribution Vasudha Vaid: conceptualization, research meth-
odology, and formal analysis; Khushbu: writing original draft prepara-
tion and data organization; Madhumita Sharma: experimental work and
investigation; Parul: software; Neha Maurya: software; Rajeev Jindal:
supervision and editing.
Funding The authors, Vasudha Vaid and Khushbu, are grateful to the
Ministry of Education, Delhi, India, for funding research.
Declarations
Conflict of interest The authors declare no competing interests.
References
1. Thompson G, Swain J, Kay M, Forster CF (2001) Treatment of
pulp and paper mill E Uent.Pdf. Bioresour Technol 77:275–286
2. Jana S, Ray J, Mondal B, Tripathy T (2019) Efficient and selec-
tive removal of cationic organic dyes from their aqueous solu-
tions by a nanocomposite hydrogel, katira gum-cl-poly(acrylic
acid-co-N, N-dimethylacrylamide)@bentonite. Appl Clay Sci
173:46–64. https:// doi. org/ 10. 1016/j. clay. 2019. 03. 009
3. Saka C, Şahin Ö, Adsoy H, Akyel ŞM (2012) Removal of meth-
ylene blue from aqueous solutions by using cold plasma, micro-
wave radiation and formaldehyde treated acorn shell. Sep Sci
Technol 47:1542–1551. https:// doi. org/ 10. 1080/ 01496 395. 2011.
652284
4. Sinha S, Singh R, Chaurasia AK, Nigam S (2016) Self-sustaina-
ble Chlorella pyrenoidosa strain NCIM 2738 based photobiore-
actor for removal of Direct Red-31 dye along with other indus-
trial pollutants to improve the water-quality. J Hazard Mater
306:386–394. https:// doi. org/ 10. 1016/j. jhazm at. 2015. 12. 011
5. Madan S, Sachan P, Singh U (2018) A review on bioremediation
of pulp and paper mill effluent – an alternative to conventional
remedial technologies. J Appl Nat Sci 10:367–374. https:// doi.
org/ 10. 31018/ jans. v10i1. 1632
6. Zangeneh H, Zinatizadeh AAL, Habibi M etal (2015) Photocata-
lytic oxidation of organic dyes and pollutants in wastewater using
different modified titanium dioxides: a comparative review. J Ind
Eng Chem 26:1–36. https:// doi. org/ 10. 1016/j. jiec. 2014. 10. 043
7. Singh S, Sharma R, Khanuja M (2018) A review and recent devel-
opments on strategies to improve the photocatalytic elimination
of organic dye pollutants by BiOX (X=Cl, Br, I, F) nanostruc-
tures. Korean J Chem Eng 35:1955–1968. https:// doi. org/ 10. 1007/
s11814- 018- 0112-y
8. Hao YF, Yan LG, Yu HQ etal (2014) Comparative study on
adsorption of basic and acid dyes by hydroxy-aluminum pillared
bentonite. J Mol Liq 199:202–207. https:// doi. org/ 10. 1016/j.
molliq. 2014. 09. 005
9. Gong N, Liu Y, Huang R (2018) Simultaneous adsorption of
Cu2+ and acid fuchsin (AF) from aqueous solutions by CMC/
bentonite composite. Int J Biol Macromol 115:580–589. https://
doi. org/ 10. 1016/j. ijbio mac. 2018. 04. 075
10. Renita AA, Kumar PS, Jabasingh SA (2019) Redemption of acid
fuchsin dye from wastewater using de-oiled biomass: kinetics
and isotherm analysis. Bioresour Technol Reports 7:100300.
https:// doi. org/ 10. 1016/j. biteb. 2019. 100300
11. Thies JA, Merrill SB, Corley EL (2002) Red food coloring stain:
new, safer procedures for staining nematodes in roots and egg
masses on root surfaces. J Nematol 34:179–181
12. Crini G, Torri G, Lichtfouse E etal (2019) Dye removal by
biosorption using cross-linked chitosan-based hydrogels.
Environ Chem Lett 17:1645–1666. https:// doi. org/ 10. 1007/
s10311- 019- 00903-y
13. Yang Y, Zhu Q, Peng X etal (2022) Hydrogels for the removal
of the methylene blue dye from wastewater: a review. Envi-
ron Chem Lett 20:2665–2685. https:// doi. org/ 10. 1007/
s10311- 022- 01414-z
14. Shalla AH, Bhat MA, Yaseen Z (2018) Hydrogels for removal of
recalcitrant organic dyes: a conceptual overview. J Environ Chem
Eng 6:5938–5949. https:// doi. org/ 10. 1016/j. jece. 2018. 08. 063
15. Elgarahy AM, Eloffy MG, Guibal E etal (2023) Use of biopoly-
mers in wastewater treatment: a brief review of current trends and
prospects. Chinese J Chem Eng 64:292–320. https:// doi. org/ 10.
1016/j. cjche. 2023. 05. 018
16. Sharma P, Mittal H, Jindal R etal (2019) Sustained delivery of
atenolol drug using gum dammar crosslinked polyacrylamide and
zirconium based biodegradable hydrogel composites. Colloids
Surfaces A Physicochem Eng Asp 562:136–145. https:// doi. org/
10. 1016/j. colsu rfa. 2018. 11. 039
17. Khan ZA, Elwakeel KZ, Mashabi RA, Elgarahy AM (2024)
Adsorption of anionic dyes onto 1,5-diphenylcarbazide function-
alized magnetic hybrid polymer: impact of water salinity and sur-
factants on adsorption isotherms. J Ind Eng Chem 131:569–584.
https:// doi. org/ 10. 1016/j. jiec. 2023. 10. 061
18. Elgarahy AM, Mostafa HY, Zaki EG etal (2023) Methylene
blue removal from aqueous solutions using a biochar/gellan gum
hydrogel composite: effect of agitation mode on sorption kinetics.
Int J Biol Macromol 232:123355. https:// doi. org/ 10. 1016/j. ijbio
mac. 2023. 123355
19. Ravichandran D, Rajesh R (2013) Marine polysaccharide (chi-
tosan) and its derivatives as water purifier. Mar Biomater 770–
787. https:// doi. org/ 10. 1201/ b14723- 43
20. Khushbu JR (2023) Sodium alginate and chitosan based ampho-
teric nanocomposites modified with graphene oxide and ben-
tonite as an efficient adsorbent for both anionic and cationic
dyes. J Polym Environ 31:264–286. https:// doi. org/ 10. 1007/
s10924- 022- 02626-8
21. Gao C, Wang XL, Da AQ etal (2021) Synergistic preparation of
modified alginate aerogel with melamine/chitosan for efficiently
selective adsorption of lead ions. Carbohydr Polym 256:117564.
https:// doi. org/ 10. 1016/j. carbp ol. 2020. 117564
22. Mashabi RA, Khan ZA, Elwakeel KZ (2022) Chitosan- or glycidyl
methacrylate-based adsorbents for the removal of dyes from aque-
ous solutions: a review. Mater Adv 3:5645–5671. https:// doi. org/
10. 1039/ d2ma0 0320a
23. Zhang Y, Zhao M, Cheng Q etal (2021) Research progress of
adsorption and removal of heavy metals by chitosan and its
derivatives: a review. Chemosphere 279:130927. https:// doi. org/
10. 1016/j. chemo sphere. 2021. 130927
24. Pereira AGB, Martins AF, Paulino AT et al (2017) Recent
advances in designing hydrogels from chitin and chitin-derivatives
and their impact on environment and agriculture: a review. Rev

Biomass Conversion and Biorefinery
Virtual Quim 9:370–386. https:// doi. org/ 10. 21577/ 1984- 6835.
20170 021
25. Kaur K, Khushbu VV etal (2022) Efficient removal of rose bengal
and malachite green dyes using green and sustainable chitosan/
CMC/bentonite-based hydrogel materials. Polym Bull. https:// doi.
org/ 10. 1007/ s00289- 022- 04378-w
26. Li R, Da AQ, Xiao ZY etal (2017) Preparation of PEI/CS aerogel
beads with a high density of reactive sites for efficient Cr(VI)
sorption: batch and column studies. RSC Adv 7:40227–40236.
https:// doi. org/ 10. 1039/ c7ra0 6914f
27. Elwakeel KZ (2009) Removal of Reactive Black 5 from aque-
ous solutions using magnetic chitosan resins. J Hazard Mater
167:383–392. https:// doi. org/ 10. 1016/j. jhazm at. 2009. 01. 051
28. Sharma AK, Gupta A, Dhiman A etal (2022) Fe3O4 embed-
ded κ-carrageenan/sodium alginate hydrogels for the removal
of basic dyes. Colloids Surfaces A Physicochem Eng Asp
654:130155. https:// doi. org/ 10. 1016/j. colsu rfa. 2022. 130155
29. Mittal H, Morajkar PP, Al A, Saeed A (2020) In - situ synthe-
sis of ZnO nanoparticles using Gum Arabic based hydrogels
as a self - template for effective malachite green dye adsorp-
tion. J Polym Environ 28:1637–1653. https:// doi. org/ 10. 1007/
s10924- 020- 01713-y
30. Vaid V, Jindal R (2022) An efficient pH-responsive kappa-car-
rageenan/tamarind kernel powder hydrogel for the removal of
brilliant green and rose bengal from aqueous solution. J Appl
Polym Sci 139:1–19. https:// doi. org/ 10. 1002/ app. 52218
31. Guo DM, Da AQ, Xiao ZY etal (2018) Efficient removal of
Pb(II), Cr(VI) and organic dyes by polydopamine modified chi-
tosan aerogels. Carbohydr Polym 202:306–314. https:// doi. org/
10. 1016/j. carbp ol. 2018. 08. 140
32. Wang XL, Guo DM, Da AQ etal (2019) High-efficacy adsorp-
tion of Cr(VI) and anionic dyes onto β-cyclodextrin/chitosan/
hexamethylenetetramine aerogel beads with task-specific, inte-
grated components. Int J Biol Macromol 128:268–278. https://
doi. org/ 10. 1016/j. ijbio mac. 2019. 01. 139
33. Liu Y, Huang S, Zhao X, Zhang Y (2018) Fabrication of three-
dimensional porous β-cyclodextrin/chitosan functionalized gra-
phene oxide hydrogel for methylene blue removal from aqueous
solution. Colloids Surfaces A Physicochem Eng Asp 539:1–10.
https:// doi. org/ 10. 1016/j. colsu rfa. 2017. 11. 066
34. Khushbu, Jindal R (2022) β-Cyclodextrin mediated efficient
removal of rose bengal using chitosan/sodium alginate/graphene
oxide nanocomposite: a comparative study. Iran Polym J (Eng-
lish Ed. https:// doi. org/ 10. 1007/ s13726- 022- 01053-9
35. Alizadeh M, Sadrameli SM (2018) Numerical modeling and
optimization of thermal comfort in building: central composite
design and CFD simulation. Energy Build 164:187–202. https://
doi. org/ 10. 1016/j. enbui ld. 2018. 01. 006
36. Pashai Gatabi M, Milani Moghaddam H, Ghorbani M (2016)
Efficient removal of cadmium using magnetic multiwalled
carbon nanotube nanoadsorbents: equilibrium, kinetic, and
thermodynamic study. J Nanoparticle Res 18:. https:// doi. org/
10. 1007/ s11051- 016- 3487-x
37. Rudzinski W, Plazinski W (2007) Theoretical description of the
kinetics of solute adsorption at heterogeneous solid/solution
interfaces. On the possibility of distinguishing between the dif-
fusional and the surface reaction kinetics models. Appl Surf Sci
253:5827–5840. https:// doi. org/ 10. 1016/j. apsusc. 2006. 12. 038
38. Yuan Z, Wang Y, Han X, Chen D (2015) The adsorption behav-
iors of the multiple stimulus-responsive poly(ethylene glycol)-
based hydrogels for removal of RhB dye. J Appl Polym Sci
132:1–8. https:// doi. org/ 10. 1002/ app. 42244
39. Arumugam TK, Krishnamoorthy P, Rajagopalan NR etal (2019)
Removal of malachite green from aqueous solutions using a
modified chitosan composite. Int J Biol Macromol 128:655–
664. https:// doi. org/ 10. 1016/j. ijbio mac. 2019. 01. 185
40. Yadav S, Asthana A, Chakraborty R, Jain B, Singh AK, Cara-
bineiro SA, Susan MABH (2020) Cationic dye removal using
novel magnetic/activated charcoal/β-cyclodextrin/alginate poly-
mer nanocomposite. Nanomaterials 10(1):170
41. Mall ID, Srivastava VC, Agarwal NK, Mishra IM (2005)
Adsorptive removal of malachite green dye from aqueous solu-
tion by bagasse fly ash and activated carbon-kinetic study and
equilibrium isotherm analyses. Colloids Surfaces A Physico-
chem Eng Asp 264:17–28. https:// doi. org/ 10. 1016/j. colsu rfa.
2005. 03. 027
42. Sulaiman NS, Zaini MAA, Arsad A (2019) Evaluation of dyes
removal by beta-cyclodextrin adsorbent. Mater Today Proc
39:907–910. https:// doi. org/ 10. 1016/j. matpr. 2020. 03. 696
43. Yao M, Ding Y, Wang Z et al (2015) EDTA-cross-linked
β-cyclodextrin: an environmentally friendly bifunctional adsor-
bent for simultaneous adsorption of metals and cationic dyes.
Environ Sci Technol 49:10570–10580
44. Elwakeel KZ, El-Bindary AA, El-Sonbati AZ, Hawas AR (2017)
Magnetic alginate beads with high basic dye removal potential and
excellent regeneration ability. Can J Chem 95:807–815. https://
doi. org/ 10. 1139/ cjc- 2016- 0641
45. Elwakeel KZ, El-Bindary AA, Ismail A, Morshidy AM (2016)
Sorptive removal of Remazol Brilliant Blue R from aqueous
solution by diethylenetriamine functionalized magnetic macro-
reticular hybrid material. RSC Adv 6:22395–22410. https:// doi.
org/ 10. 1039/ c5ra2 6508h
Publisher's Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affiliations.
Springer Nature or its licensor (e.g. a society or other partner) holds
exclusive rights to this article under a publishing agreement with the
author(s) or other rightsholder(s); author self-archiving of the accepted
manuscript version of this article is solely governed by the terms of
such publishing agreement and applicable law.