(2024) 18:124
El Mously et al. BMC Chemistry
https://doi.org/10.1186/s13065-024-01224-0

BMC Chemistry

RESEARCH

Open AccessFacile synthesis of copper nitroprussidechitosan nanocomposite and its catalytic
reduction of environmentally hazardous
azodyes
Dina A. El Mously1*, Amr M. Mahmoud1,2, Moustafa Ali Khallaf3, Howida S. Mandour4 and Hany A. Batakoushy5

Abstract
One of the biggest issues affecting the entire world currently is water contamination caused by textile industries’
incapacity to properly dispose their wastewater. The presence of toxic textile dyes in the aquatic environment
has attracted significant research interest due to their high environmental stability and their negative effects
on human health and ecosystems. Therefore, it is crucial to convert the hazardous dyes such as methyl orange(MO) azo dye into environmentally safe products. In this context, we describe the use of Copper Nitroprusside
Chitosan (Cu/SNP/Cts) nanocomposite as a nanocatalyst for the chemical reduction of azodyes by sodium
borohydride ­(NaBH4). The Cu/SNP/Cts was readily obtained by chemical coprecipitation in a stoichiometricmanner. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR)
spectroscopy were applied to investigate chemical, phase, composition, and molecular interactions. Additionally,
Scanning electron microscope (SEM) was used to examine the nanomaterial’s microstructure. UV–vis spectroscopy
was utilized for studying the Cu Nitroprusside Chitosan’s catalytic activity for the reduction of azodye. The Cu/SNP/
Cts nanocomposite demonstrated outstanding performance with total reduction time 160 s and pseudo-firstorder constant of 0.0188 ­s−1. Additionally, the stability and reusability study demonstrated exceptional reusability
up to 5 cycles with minimal activity loss. The developed Cu/SNP/Cts nanocomposite act as efficient nanocatalysts
for the reduction of harmful Methyl orange azodye.
Keywords Azo dyes, Methyl orange degradation, Wastewater treatment, Catalytic reduction, Nanocatalyst, Cu
Nitroprusside, Chitosan*Correspondence:
Dina A. El Mously
dina.abbas@pharma.cu.edu.eg
1
Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy,
Cairo University, Cairo 11562, Egypt
2
Department of Chemistry, School of Pharmacy, Newgiza University(NGU), New Giza, Km 22 Cairo‑Alex Road, Cairo, Egypt
3
Pharmaceutical Chemistry Department, Faculty of Pharmacy, Cairo
University, Kasr El‑Aini Street, Cairo 11562, Egypt
4
Physical Chemistry Department, National Research Centre, Giza 12622,
Egypt
5
Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy,
Menoufia University, Shebin Elkom, Egypt

Introduction
The environment and human health have beensignificantly impacted over the past few decades by
the rapid and uncontrollable growth of the world’s
population as well as technological advancements in theindustrial and agricultural sectors [1, 2]. Textile industry
is one of the largest contributors to environmental
pollution of all the sources due to the use of various toxic
dyes [3]. About 50,000 tons of dyes are released into theenvironment each year as a result of textile wastewater
discharge, which contributes 20% of water pollution [4].

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El Mously et al. BMC Chemistry(2024) 18:124

The effluents from the textile industries comprise avast number of intermediate substances because of thepresence of numerous unit operations [5]. Furthermore,oxidation and hydrolysis of commercial dyes with azo
functional groups can produce toxic and mutagenic
byproducts, which contributes to environmental andeconomic risks. These wastewaters pose a major threat
to the environment, threaten sustainable development,
and require the development of innovative treatment
technologies for the removal and degradation of the toxic
dyes [6].
Nevertheless, it is challenging to degrade most of theseorganic dyes using an efficient and compelling strategy
due to their reasonable stability [7]. Azodye degradationfrom environmental wastewater has been demonstratedusing various strategies such as adsorption [8], ion
exchange microbial degradation [9], photocatalytic
degradation [10], electrocatalytic reduction [11].
Nevertheless, the forementioned strategies have various
limitations such as the costly nature of some adsorbents
and membranes (adsorption, ion exchange), inadequate
degradation rate (microbial degradation) and thepossibility of corrosion of electrodes (electrocatalytic
reduction).
Despite the limitations with aforementioned methods,
it was proven that reduction of azodye into harmlessproducts utilizing Sodium Borohydride ­(NaBH4) could
be efficiently inducted in the presence of a convenient
catalyst. This approach is distinguished by its ease of use,time saving, efficient conversion rates and lack of sludge[12–19].
Reduction of azodyes including methylorange (MO)using ­NaBH4 needs a catalytic system to overcome
the large kinetic barrier which makes the reaction
challenging. Consequently, catalysts facilitate theelectron transition between the B­ H4− as an electron
donor and MO as an electron acceptor and hence making
the reaction favourable [16, 20]. Therefore, it is crucial
to produce an affordable, highly stable catalyst for the
reduction of azodyes.
Over the last decades, there has been a lot of interestin the use of nanocatalysts in the reduction of azodyes
such as methyl orange [13, 19]. Nanocatalysts have beenfound to be efficient for the reduction of methyl orange
due to their high surface area for electron transfer thanconventional powdered catalysts. Various nanocatalysts,
including metal nanoparticles, have been reported in theliterature for catalytic reduction of MO such as Cu NPs[21, 22], Au NPs [23], ­Fe3O4@-Ag NPs [24]. Despite theireffective catalytic function, the need for more affordable
and simpler nanocatalysts has prompted more researchin this field.

Page 2 of 13

Pentacyanonitrosylferrate(II) known as nitroprussideion [Fe(CN)5NO]2− is a coordination complex capable offorming various substituted metal nitrosyl pentacyanides
imposing various 3D structures with diverse properties
and applications that vary according to the type oftransition metal complexing with it [25]. With animmense similarity between nitroprusside and Prussian
blue (ferric ferrocyanide ­(Fe3+)4[(Fe2+)(CN)6]3) in termsof chemical composition, electronic structure, redox
properties, and electrocatalytic activities, it can beassumed that nitroprusside transition metal complexes
might possess similar catalytic activity as Prussian bluetransition metal analogues that have been utilized fordecomposition of environmental pollutants [6, 25].
Chitosan, a biopolymer sourced from chitin, functions
as a stabilizing and size-controllable agent to enhancethe dispersion and stability of nanoparticles, thereby
complementing their catalytic activity [26, 27]. This
combination enhances the overall efficiency of thecatalytic system, providing a sustained catalytic activity
over multiple reaction cycles. Chitosan provides morefunctional groups that can take part in the reduction
process, which further enhances the catalytic system’s
reactivity [28]. The azodyes may interact with theamino and hydroxyl groups in chitosan facilitating
their adsorption onto the catalytic surface andadvocating better contact between the dye moleculesand nanoparticles active sites. Furthermore, the
NP-Chitosan composite shows enhanced stability acrossa wide pH range, which makes it adaptable for use invarious wastewater treatment conditions. Therefore,
the NP-Chitosan enhances the reaction kinetics, andthe addition of chitosan provides an eco-friendly andbiocompatible matrix for the nanoparticle entrapment,
providing a sustainable approach towards water quality
improvement [28].
Based on previous knowledge of Prussian blue
analogues catalytic activity and chitosan capability
to stabilize nanoparticles and enhance their catalytic
activity, the current study describes the synthesis of Cu
Nitroprusside Chitosan (Cu/SNP/Cts) nanocomposite
for the first time and their potential use as nanocatalysts
for the catalytic reduction of MO utilizing N­ aBH4 as a
reducing agent.

Experimental
Chemicals and reagents

Sodium borohydride (­NaBH4) 98% purity, Methyl
orange ≥ 98% purity, Chitosan ≥ 99% purity, Copper
sulphate ≥ 99% and Sodium nitroprusside werepurchased from Sigma Aldrich (Germany). Ultrapure
water was attained from “Aquatron” Automatic Water
Still A4000, Bibby Sterillin Ltd., (Staffordshire, UK).

El Mously et al. BMC Chemistry(2024) 18:124

Synthesis of copper nitroprusside/chitosan nanocomposite

The Cu/SNP/Cts nanocomposite was synthesizedaccording to the reported method [29]. In a 100 mL
solution of HCl, (0.5 mol ­L−1), 300 mg of Chitosan(200 k) powder was dissolved and stirred at ambient
temperature for one hour, then 20 mL solution of 1 mM
sodium nitroprusside was added to 80 mL chitosan
solution and left on stirrer for 30 min. After that, 20 mL
solution of 1 mM copper sulfate was added in a dropwisemanner over 30 min under stirring where solution turned
bluish green over time. Then, 200 mL acetone was mixed
with the solution after 1 h and centrifuged at 4000 rpm
for 15 min to collect and wash the formed nanoparticles
at which washing with acetone and centrifugation
were repeated several times. The formed Cu/SNP/Cts
nanoparticles were finally washed with methanol and left
to dry out.
Characterization of copper nitroprusside/chitosan
nanocomposite

The chemical composition of Cu/SNP/Cts wasinvestigated utilizing Thermo Fisher Scientific ESCALAB(USA) for X-ray photoelectron spectroscopy (XPS)
analysis. Fourier transform infrared (FTIR) spectra
were attained utilizing a Vertex 80V FTIR spectrometer(Bruker, Germany) for function group analysis. The Cu/
SNP/Cts complex’s crystal structure was examinedusing X-ray diffraction (XRD) (Model: Rigaku SmartLab.). An electron microscope (SEM; Japan Electro
Company) coupled to energy-dispersive X-ray analysis
for elemental mapping (EDX) was utilized to study thesurface morphology of the synthesized Cu/SNP/Cts to

Fig. 1 TEM image of the synthesized nanocomposite (Cu/SNP/Cts)

Page 3 of 13

identify the primary elemental composition and purity of
the nanoparticles. A Shimadzu UV–Visible double-beamspectrophotometer, model 1601 PC (Japan), was used tomonitor the reduction reaction’s completion.
Study of the catalytic activity of Cu/SNP/Cts
towards reduction of MO

The reduction of MO was performed in an aqueous
medium utilizing sodium borohydride as a reducing
agent and Cu/SNP/Cts as nanocatalyst. The progressionof the reduction process was monitored by UV–vis
spectrophotometry. In this study, 2.5 mL of BR buffer
pH 9.0 was added in a quartz cuvette along with 100 μLof an aqueous solution of MO (C = 3 mM), 200 μL of anaqueous solution of N
­ aBH4 (C=300 mM), and 5 μL of anaqueous suspension of Cu/SNP/Cts (C = 1000 μg ­mL−1).
At consistent intervals, the UV–vis spectra have beenrecorded over the range of 200–550 nm. The absorbanceof MO at various time intervals at 464 nm was measured
to track the reaction’s progression at room temperature.
Blank experiments were furthermore done by repeating
the same procedures but with using ­NaBH4 alone without
a catalyst.

Results and discussion
Structural, composition, and molecular interaction analysis
Structural analysis and surface compositions

Transmission electron microscopic analysis of the com‑posite Cu/SNP/Cts Transmission electron microscopic(TEM), technique is a useful and good tool to understandand determine the size, shape, structure, dispersion, uniformity of material, and crystal phase. It can be observed

El Mously et al. BMC Chemistry(2024) 18:124

Page 4 of 13

from Fig. 1a, that; the core shape of the composite (Cu/
SNP/Cts) appeared as irregular thin sheets containing
particles in the range of nanoscale 57–69 nm; this result
indicates that, the synthesized sample can be identified asa nanocomposite (Cu/SNP/Cts). In addition, from Fig. 1b,
it can be noticed that these nanoparticles are in a sphericalshape. Based on the previous studies [30, 31], the copper
nitroprusside nanoparticles usually appear in this shape.
XRD analysis (X‑ray diffraction) XRD is considered afaster analytical technique used for phase identification of
crystalline materials and can provide information on unit
cell dimensions. The spectrum of x-ray diffraction for thechitosan (Cts), is presented in Fig. 2. As, it can be seenfrom Fig. 2, that, the XRD manner of (Cts), displayed two
broad diffraction peaks at 2θ = 9.78° and 21.66°; the existence of these two diffraction angle had been related to the
crystallinity of the chitosan [32]. The XRD type of the prepared nanocomposite (Cu/SNP/Cts), is shown in Fig. 3. It
can be noticed from Fig. 3; the presence of the diffraction
peaks at 2θ = 36.40°, 43.47°, 50.91° and 75.21°, which are
related to the crystal plane (111), (111), (200) and (220),
respectively, emphasizes the formation of the cubic lattice of copper nanoparticles Cu(NPs), owing to (JCPDS
No. 040836), [33]. Also, according to previous studies; thediffraction peak at 19.55° was assigned to the existence

Fig. 2 XRD spectrum of pure chitosan (Cts)

Fig. 3 XRD spectrum of the synthesized nanocomposite (Cu/SNP/Cts)

of chitosan (Cts) in the medium [34]. It can be observed
from Fig. 3, that the diffraction peak of the chitosan (Cts)recorded the highest peak intensity among the others.
This observation confirms the interaction between thenanoparticles of the prepared nanocomposite and the stabilizing medium (Cts) [35]. Also, the spectrum of Fig. 3,
shows the diffraction peaks at 2θ = 17.61°,24.63°,35.62°
and 39.74°, corresponding to the crystal plane (200),

El Mously et al. BMC Chemistry(2024) 18:124

Page 5 of 13(220), (222), and (400), respectively, assures the formationof cubic structure of Copper Nitroprusside nanoparticles
SNP(NPs), [25, 36]. This result was in matching with thereference data of PB (ICDD PDF2 01-073-0687). Therefore, through this result; it can be deducted that, the synthesized nano-composite is (Cu/SNP/Cts). The crystal
size was measured using Debye-Scherer Eq. (1):(1)

D = K/β cos θ

where D is the crystal size of the nanoparticle, λ is
0.15406 nm (wavelength of X-ray), K is the Scherer’s constant or shape factor with a value of 0.9, θ is the diffraction angle, and β1/2 is the full width half maxima FWHM[37]. It was found that the calculated particle size was in
the range of 57–82 nm; this result was in agreement withthe result investigated from the analytical techniquetransmission electron microscopic (TEM), which confirms that the synthesized composite (Cu/SNP/Cts) is in
the nanoscale range.
FT‑IR spectra Fourier-transform infrared spectroscopy(FT-IR), of the synthesized nano-composite (Cu/SNP/Cts), and pure chitosan (Cts), was measured and shown in
Fig. 4. As, can be noticed from Fig. 4b, that, there are new
two bands; one of these bands was sharp and appeared
in a weak shape at 3651.26 ­cm−1, and the other band was
sharp and appeared in strong shape at 458.57 ­cm−1.
The appearance of these two new bands at (3651.26
and 458.57 ­cm−1), referred to the reaction that occurred
between the amino and hydroxyl groups of thechitosan (Cts), and the surface of the Cu nitroprusside
nanoparticles [35], or by another words; the Cu
nitroprusside NPs had been incorporated into thepolymer (Cts).

1.2

Transmittance (a.u.)

(a)
1.0
0.8
0.6

(b)

0.4
0.2
4000

3000

2000

1000

Wave number (cm-1 )Fig. 4 FT-IR spectra of a pure chitosan and b the preparednano-composite (Cu/SNP/Cts)

In addition, it can be seen from Fig. 4b, the appearance of stretching and a broad band in a weak shapeat 3454.12 ­cm−1, which corresponds to the overlap of the hydroxyl and amino groups [38], while theamino group (­NH2), in Fig. 4a, for pure chitosan (Cts),
appeared as a broad band at the wave numbers 3229
and 3238 ­cm−1. According to the literature, the cyanidegroup C≡N appears in the range of the wave number
2220–2260 ­cm−1, from Fig. 4b, it can be observed that,the peak of cyanide group appeared as a strong band ina sharp shape at 2200.64 ­cm−1; decreased than its valueof the wave number of literature by about 19 ­cm−1. This
result indicates that, the shifting of this peak was attributed to its coordination with Cu in the Cu nitroprusside
nanoparticles [39].
As well as, from Fig. 4b, the appearance of a strong
band in medium shape at 1956.29 ­cm−1, was related to(NO), group; the presence of these two absorption bands
at 2200.64 and 1956.29 ­cm−1, confirmed the formationof pentacyanonitrosylferrate or in other words theformation of a binuclear complex of iron and copper as it
was reported previously [40, 41].
Also, from Fig. 4b, the two weak peaks appeared at1607.62 and 1595.29 ­cm−1, corresponded to the vibration
band C=O with shifting decreased by about 26 ­cm−1, incomparison with that of Fig. 4a, of pure chitosan whichappeared at 1633 ­cm−1, and the peak of –NH2 bending
with shifting raised by about 21 ­cm−1, in comparison
with that of Fig. 4a, which appeared at 1574 ­cm−1 [31].
All the other absorption bands in Fig. 4b, whichappeared at (1379, 1312, 1152 and 1072 ­cm−1), had beenchanged with shifting decreased or increased than thatof Fig. 1a for pure (Cts), which appeared at (1382, 1331,
1162 and 1­ 067cm−1), respectively. The two weak peaks at1379 and 1312 ­cm−1 had been related to C–H bending,and the two broad weak peaks at 1152 and 1072 c­ m−1
belonged to C–O–C group owing to skeletal stretching[38]. The strong medium peak at 530 ­cm−1 in Fig. 1b,
was attributed to the metal–carbon interaction; in otherwords, the linke between Cu and C [30].
X‑ray photoelectron spectroscopy data analysis XPS isa useful technique which used to analyse the elements
constituting of the sample surface (composition, chemical bonding and kinetic energy of the emitted photoelectrons). Based on Fig. 5a, which shows different oxidation
states of copper; it can be seen four peaks at binding
energy 932.8, 936.2, 952.34 and 956.4 eV; the peak at 932.8
eV was attributed to Cu ­2p3/2 which confirms the presenceof Cu (0) and Cu (I), where the peak around 936 eV, can be
assigned to Cu (II) [42]. The peak at 952.34 eV, was related
to Cu ­2p1/2 which revels the existence of Cu (0) and Cu (I),where the peak at the binding energy 956.4 eV, belonged

El Mously et al. BMC Chemistry(2024) 18:124

Page 6 of 13

7000

Cu2p

7000

Fe 2p
6000

Counts / sec

Counts / sec

6500

6000

5500

5000

4000

5000
3000

960

950

940

930

730

725

720

715

Binding Energy (eV)Binding Energy (eV)

(a)

(b)

710

705

N 1s

6000

Counts / sec

5000

4000

3000

2000

1000
408

406

404

402

400

398

396

394

Binding Energy (eV)

(C)
7000

6000

O1s

5000

6000

4000

5000

Counts / sec

Counts / sec

C 1s

3000

4000

2000

3000

1000

2000

292

290

288

286

284

282

538

536

534

Binding Energy (eV)532

Binding Energy (eV)

(d)

(e)
8e+4

Cu2p

Counts / sec

6e+4

Fe2p

O1s
N1s C1s

4e+4

2e+4

0
1200

1000

800

600

Binding Energy (eV)(f)
Fig. 5 XPS spectra of the synthesized nanocomposite (Cu/SNP/Cts)

400

200

0

530

528

El Mously et al. BMC Chemistry(2024) 18:124

Page 7 of 13

to Cu 2
­ p5/2 pointed to the presence of Cu (II). The Fe2p
spectrum in Fig. 5b, shows four peaks [43–45] at binding energies of 708.837, 711.192, 720.919, and 724.178 eV.
The two high intensity peaks with binding energy 711.192
and 724.178 eV are confirming the presence of Fe 2p1/2 andFe 2p3/2 with ­Fe2+ low spin states, respectively [43–45].
Also, the two binding energy 708.837 and 720.919 eV, areassigned to the high-spin ­Fe2+ state of Fe 2p3/2 and Fe 2p1/2,
respectively [43–45]. In addition, from Fig. 5c, three peaks
at binding energy 398.726, 399.95 and 403.276 eV, can beobserved, which corresponded to the presence of nitrogen atom at 398.726 eV, and the other two broad peaks are
related to the existence of C=N and C≡N groups with s­ p3
and ­sp2 hybridization, respectively [46]. As well, Fig. 5d,
illustrated the appearance of three broad peaks at binding energy 285.5, 287.1 and 288.7 eV, which are related
to the presence of C=N, C≡N groups with ­sp2 and ­sp3
hybridization, respectively and the third broad peak atbinding energy 288.7 eV, was attributed to O–C=O group[46]. Figure 5f, shows three broad peaks at binding energy
531.3, 532.9 and 535.4 eV, corresponding to formation of
Fe (OH)3, and presence of C–O–C group respectively,

Table 1 The compositions of the main elements of thesynthesized Cu/SNP/Cts
Element

Weight %Atomic %

C

24.37

36.2

O

16.79

18.72

N

28.26

35.99

Fe

13.18

4.21

Cu

17.4

4.89

while the high binding energy 535.4 eV, was assigned toexistence of ether group R-O-R [47].
Surface morphology and constituent of the nano‑compos‑
ite (Cu/SNP/ (Cts) It was clear from the image of scanning electron microscopy analysis (SEM), that, the nanoparticles of the nanocomposite (Cu/SNP/Cts), had beengrown in the shape of nano-sheet with higher agglomeration resulted in formation of large flocks of these nanoparticles. The large surface area and also high ability ofcopper nanoparticles to bond may be the reason of theagglomeration of the nanoparticles [31]. The constituent
composition of the synthesized nanocomposite (Cu/SNP/Cts), was investigated by energy dispersive X-ray spectrometer (EDX), analysis, which confirms the presenceof all the basic elements to form the nanocomposite (Cu/
SNP/Cts), such as, copper, iron and the elements; carbon,
oxygen, and nitrogen, as reported in Table 1 and shownin Fig. 6.
Catalytic reduction of methyl orange using Cu/SNP/Cts
nanocomposite

Azo dyes like methyl orange (MO) are regarded as oneof the most basic pollutants in wastewater and natural
water bodies.MO pose significant environmental
risks due to its high potential for being teratogenic,
and carcinogenic and toxic azodye. Hence, it is vitalto transform the hazardous MO azo dye into lessharmful substances, such as 4-aminobenzenesulfonicacid and N,N dimethylbenzene 1,4 diamine (DMBD).
4-aminobenzenesulfonic acid, also known as sulfanilicacid, is an indirect FDA-approved food additive.
MO was catalytically reduced utilizing ­NaBH4 andCu/SNP/Cts nanocatalyst (Fig. 7). Using UV–VIS

Fig. 6 SEM image and EDX analysis of the synthesized nanocomposite (Cu/SNP/Cts)El Mously et al. BMC Chemistry(2024) 18:124

Page 8 of 13

Fig. 7 Reduction of MO by ­NaBH4 utilizing Cu/SNP/Cts as nanocatalyst

spectrophotometry, the reduction reaction’s process
was tracked over time. The azo bond and the dimethylamino electron-donating groups are responsible for theabsorbance at 464 nm in the MO spectrum. The intensity of the MO peak at 464 nm was instantly decreased
after adding the Cu/SNP/Cts nanocatalyst, and it vanished entirely after 160 s (Fig. 8). The formation of
hydrazine derivatives was indicated by the appearanceof a new peak at 250 nm. The MO’s yellow colour fully
disappeared after 160 s, indicating that it had been
completely diminished. Additionally, the reduction of

MO was explored without utilizing the Cu/SNP/Cts
nanocatalyst. A very small reduction in the peak intensity of MO was observed at 464 nm, Fig. 9.
NaBH4 can reduce MO in a thermodynamically feasible
manner. However, the reaction is kinetically challenging
due to the high kinetic barrier between MO, an electron
acceptor, and ­NaBH4, an electron donor.
A pseudo-first-order kinetic model was implemented
to compute the rate constant for MO reduction becauseof the excessive concentration of ­NaBH4 compared tothat of MO. It was presumed that the rate of reaction

Fig. 8 UV–vis spectra for the reduction of Methyl orange compound by Cu/SNP/Cts at distinct time intervals

El Mously et al. BMC Chemistry(2024) 18:124

Page 9 of 13

Fig. 9 UV–visible spectra for Methyl orange reduction without using a nanocatalyst

relied only on the concentration of MO as the concentration of N
­ aBH4 remains constant throughout the dye
reduction reaction, in accordance with the LangmuireHinshelwood model [48, 49]. The equation of pseudofirst-order kinetic is described as ln (Ct/Co) =  − kt. It
can also be described as ln (At/Ao) =  − kt since they are
equal at 464 nm. Hence, ln (­ At/Ao) versus the reduction

time was plotted in Fig. 10 to show the progression of
MO reduction in the presence of Cu/SNP/Cts nanocatalyst. The slope of the plot was utilized to calculate
the apparent rate constant (k), which turned out to be
0.0188 ­s−1.

Fig. 10 Kinetics plot of ln(At/Ao) against time for reduction of Methyl orange utilizing Cu/SNP/Cts as nanocatalyst

El Mously et al. BMC Chemistry(2024) 18:124

Page 10 of 13

Effect of Catalyst Dose and Medium pH on Catalytic
Activity of Cu/SNP/Cts Nanocatalyst

Under various pH conditions (acidic; pH 5.0, neutral;
pH 7.0, and basic; pH 9.0), the catalytic efficiency of Cu/
SNP/Cts nanocatalyst towards MO reduction by ­NaBH4
was evaluated. In all experiments, the least possible
concentration of nanocatalyst was maintained (5 µg). The
alkaline condition (pH 9.0) resulted in the fastest catalytic
reduction where the computed k was found to be 0.0188­s–1 with a total reduction time 160 s. The rate decreased
with decreasing pH, with k values of 0.007 ­s–1 at pH 7.0
and 0.002 ­s–1 at pH 5.0, respectively. At pH 7.0, 69.9% of
MO was reduced after 160 s, but at pH 5.0, only 47.9% of
MO (Table 2).
One of the most widely used water-soluble azo dyes,
MO is usually dumped in industrial wastewater [50] andis widely used in the textile and paper industries. These
industries frequently produce effluent with an alkaline
pH [51, 52]. The strong catalytic activity of the suggested
nanocatalyst in alkaline pH is therefore of great benefit
to remove dangerous MO azo dye in alkaline industrial
Table 2 Comparison between the catalytic efficiency of Cu/
SNP/Cts nanocomposite in different pH in terms of percentage
MO reduction in 160 s and reaction rate k
pH

k

% MO
reduction in
160 s

5.0

0.002 ­s

−1

47.9

7.0

0.007 ­s−1

69.9

9.0

−1

100

0.0188 ­s

wastewater, according to the results. The alkaline pH of
textile effluent, which affects the growth and metabolismof microbial cells, frequently limits the biological treatment of the waste [53].
Reusability of the proposed Cu/SNP/Cts nanocatalyst

The nano-catalyst’s efficiency, recyclability, and usability
are crucial aspects for practical applications in the degradation process of textile dyes. Economic value can befound by a stable catalyst that can be used repeatedly
without losing its effectiveness because it lowers theprocess’s cost. Recycling studies were therefore carriedout at the observed conditions to evaluate the recyclability and stability of Cu/SNP/Cts as nano-catalysts andits efficiency in between cycles. This was accomplishedby adding a fresh batch of Cu/SNP/Cts NPs to the reaction mixture after one catalytic reduction cycle was completed without catalyst regeneration. The Cu/SNP/Cts
nanocatalyst was found to demonstrate nearly the samecatalytic performance after five catalytic reduction cycles
with a very slight increase in the total reduction time.
Nevertheless, even in the absence of regeneration, theCu/SNP/Cts was still able to reduce MO speedily up till
91% after the fifth cycle revealing good catalytic activity
and high stability of these nanocatalysts in this reduction
process, Fig. 11.
Evaluation of the proposed catalytic efficiency of Cu/SNP/
Cts in relation to other reported catalysts for MO reduction

The newly synthesized PBA Cu/SNP/Cts was evaluatedfor its catalytic efficiency against other catalysts reported

Fig. 11 Rate of Methyl orange conversion using Cu/SNP/Cts as a nanocatalyst following five distinct cycles

El Mously et al. BMC Chemistry(2024) 18:124

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Table 3 Comparison between the catalytic efficiency of the suggested Cu/SNP/Cts and other documented catalysts for MO reduction
Catalyst

NaBH4 amount

Catalyst amountk ­(s−1)

Reaction completiontime (min)Refs.

Cu NPs

0.5 mL (0.2 M)

5000 µg

8.6 × ­10–3

4

[21]

2

1. 5 × ­10–3

12

[54]

CuAg/ZnO/carbon blackcellulose acetate sheets

0.5 mL (1 M)

0.5 ­cmrGO–Ag/PVA

N/A

50 µg

0.8 × ­10−3

12

[55]

C@Fe

1 mL (0.5 M)

5000 µg15.3 × ­10–3

4

[15]

DLP-AuNPs? (1 × ­10–3 M)

100 µg

1.7 × ­10−3

8

[56]

SDS@Ag–Cu NPs

0.5 mL (0.025 M)

448 µg/mL

6.4 × ­10–3

21

[57]

2.66

This work

Cu/SNP/Cts

0.2 mL (0.3 M)

5 µg

in the literature for the reduction of MO. Table 3 reveals
that the suggested nanocatalyst exhibited exceptional
performance. A higher rate constant (k) and a notabledecrease in the overall time needed for the full reductionof MO were attained with just 5 µg of the recommended
nanocatalyst. To sum up, the suggested PBA outperforms
other catalysts documented in the literature in terms ofcatalytic activity.

18.8 × ­10–3Conclusion
The widespread distribution of toxic textile dyes in theaquatic environment has attracted significant researchinterest because of its detrimental health effects on people as well as its overall environmental impact. In thisstudy, novel Copper Nitroprusside Chitosan nanocomposite was effectively synthesized through chemical
coprecipitation to be used as a nanocatalyst for the reduction of widely utilized textile azodye Methyl Orange. The
Copper Nitroprusside Chitosan nanocomposite was

Scheme 1 Proposed mechanism of Methyl orange catalytic reduction utilizing ­NaBH4 and Cu/SNP/Cts nanocomposite

El Mously et al. BMC Chemistry(2024) 18:124

shown to be a highly intriguing candidate for rapid reduction of the potentially hazardous MO to more benign
products. Moreover, the influence of various parameterssuch as catalyst dose and pH of medium was studied. Following the optimization procedure, it was found that theoverall reduction time of MO was 160 s with a calculated
rate constant (k) equal to 0.0188 ­s–1. Furthermore, thenanocatalyst demonstrated excellent stability and recyclability for 5 repeated cycles with no remarkable decline
in catalytic performance. The proposed mechanism ofMethyl orange catalytic reduction utilizing ­NaBH4 andCu/SNP/Cts nanocomposite is presented in Scheme 1.
Ultimately, the introduced Copper Nitroprusside Chitosan nanocomposite could be utilized as a nanocatalyst
for rapid degradation of the toxic azodyes from environment and consequently could unlock the way to various
catalytic and environmental remediation applications.
Abbreviations
MO	Methyl orange
Cu/SNP/Cts	Cu nitroprusside chitosan
NaBH4	Sodium borohydride
XPS	X-ray photoelectron spectroscopy
FTIR	Fourier transform infrared spectrometer
XRD	X-ray diffraction
EDX	Energy-dispersive X-ray
DMBD	N,N dimethylbenzene 1,4 diamine
Acknowledgements
The authors would like to thank analytical chemistry department, Faculty of
Pharmacy, Cairo University and National Research Centre for providing thechemicals and facilities to accomplish this work.
Author contributions
Material synthesis was carried out by M. A. K. and A.M.M. Data collection
and analysis were performed by D.A.E., A.M.M. M.A.K. and H. A. B. Material
characterization was conducted by H. S. M. The first draft of the manuscript
was written by D.A.E. and H. S. M. All authors reviewed the manuscript.
Funding
Open access funding provided by The Science, Technology & Innovation
Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank
(EKB). This research did not receive any specific grant from funding agencies in
the public, commercial, or not-for-profit sectors.
Data availability
All data generated or analyzed during this study are included in this publishedarticle.

Declarations
Ethics approval and consent to participate.
Not applicable.
Consent for publication.
Not applicable.
Competing interests
The authors declare that they have no competing interests regarding the
publication of this article.
Received: 5 March 2024 Accepted: 12 June 2024

Page 12 of 13

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