The Adsorption Ability of Cibacron Red Dye from Aqueous Solution Using Copper Oxide Nanoparticles

This research describes the environmentally friendly production of CuO nanoparticles utilizing watercress plant extract and calcination at 400 C for 3 hours. SEM and TEM were used to analyze the size of nanoparticles. X-ray diffraction (XRD) was used to determine their crystal structure. Energy-dispersive X-ray spectroscopy (EDX) analysis of the created product's structure revealed just copper and oxygen constituents, demonstrating the purity of the synthetic material. The addition of CuO NPs improved the absorption of the dye Cibacron red. At 35 minutes of contact time, quicker adsorption of Cibacron red dye onto CuO nanoparticles was observed. The Freundlich isotherm and kinetic of pseudo-second order with R2 values more than 0.9785 and 0.999, respectively, were the most effective in describing the adsorption process. The thermodynamic parameters were calculated using thermodynamic analysis. It can be concluded that CuO NPs are an effective adsorbate surface for the Cibacron red dye


Introduction
The creation of materials with unique size, structure, and content is now possible because of nanotechnology 1 , a critical development in contemporary science.Materials with a diameter of less than a nanometer are produced, processed, and used 2,3 .Compared to individual bulk atoms and molecules, nanoscale physical, chemical, and biological properties vary [4][5][6] .This makes it possible to develop fresh classes of cutting-edge substances and materials that meet the demands of high-tech applications [7][8][9][10] .Numerous businesses and fields, including as the chemical industry, electrochemical photo applications, environmental health, medicine, and energy, are using nanotechnology 11,12 .Since some time ago, medical institutions have used metal nanoparticles, including gold, silver, and zinc, as tool for biomedical applications 24,25 .Copper oxide nanoparticles have been shown to have potential uses in a variety of fields, including gas sensors, catalysis, solar cells, batteries, food preservation, high temperature superconductors, waste treatment, photovoltaic devices, agriculture, field emission emitters, and dye removal 26,27 .Dyes, which include all substances used to color textiles, leather, food, and other materials, are regarded as organic pollutants in aqueous systems and may pose a number of risks to all elements of the environment due to their high toxicity, particularly when they are present in high concentrations 28 .Among the components of industrial effluent, organic compounds play a crucial role.Due to the possibility of some organic contaminants causing malignant diseases, there is a high danger of longterm effects 29 .According to World Health Organization (WHO) reports, drinking water contamination is the primary source of the majority of diseases that are spread in underdeveloped nations 30 .As a result, many treatments have been employed by researchers to treat industrial water 31 .
Organic contaminants in industrial water have been treated and eliminated in a variety of ways.They include reverse osmosis, ion exchange, chemical oxidation, photo-oxidation, and the adsorption process 32 .Adsorption is a technique that is effective and economical.It is frequently used, according to WHO data, to detoxify polluted water [33][34][35][36] .Heterogeneous photocatalytic degradation involves three fundamental processes: surface reaction, ultimate pore and desorption surface adsorption.The adsorption mechanism and reactions were extensively researched using a variety of models and characterization methodologies, depending on the goals of each investigation.However, the fact that the process is optimized is a shared characteristic 37 .The aim of this research to prepare copper oxide nanoparticles from watercress extract and determine whether CuO nanoparticles could effectively remove the Cibacron red dye, which is one of the dyes used at the textile industry in the Wasit Governorate and the majority of which is disposed of as waste water.

Preparation of Watercress Plant Extract
A plant extract from the watercress has been gathered and cleaned with de-ionized water to remove dust particles.The dry leaves are gently combined in a mixer to create homogenous powders then, 10 g of leaves were pulverized and mixed with 150 ml of de-ionized water, then heated for 30 minutes at 60 °C with stirring.The solution was filtered and stored in the fridge.

Synthesis of CuO Nanoparticles
The green synthesis technique was used to make copper oxide nanoparticles 38 .In accordance, an amount of 200 ml of watercress extract was added slowly (one drop per second) to 0.01 mole of Cu(NO3)2 and stirred for 30 minutes.The green powder was precipitated, separated, and washed with deionized water numerous times.The precipitate was dried for an hour at 150°C and calcined for three hours at 400°C.The black powder of copper oxide nanoparticles was obtained

Adsorption of Cibacron Red Dye on CuO NPs
The equilibrium isotherm of a particular adsorbent serves as a representation of its adsorbent properties while building adsorption processes.In deionized water, a stock solution of cibacron red dye 50 ppm was created.10 ml of dye solution were combined with 0.01 g of CuO nanoparticles, which were then heated at 298 K for 30 minutes.A UV-visible absorption spectrophotometer measured the dye concentration after filtering the solution as Eq. 1 39 .

Qe = ( C₀_ Ce)Vsol/m 1
Where C0 and Ce are the starting and equilibrium concentrations of Cibacron red dye (mg/L), Qe (mg/g) is the equilibrium adsorption capacity, and M is the mass of the CuO nanoparticles (g), V sol is the volume of cibacron red (L).

Characterization of CuO Nanoparticles
The CuO nanoparticles sample was examined using X-ray diffraction (XRD-6000).Transmission electron microscopy was used to examine the

Results and Discussion
The X-ray Diffraction of CuO Nanoparticles The X-ray crystallography was used to determine the structure of nano-synthesized, in which the crystal's atoms cause an incoming X-ray beam to diffract in various directions.According to XRD analysis, the monoclinic CuO (JCPDS 45-0397) planes ( 110), ( 111), ( 200), (-202), ( 020), ( 202 where D is the particle size (nm), k is a constant of value 0.94, β is the full-width at half maximum (FWHM) of the peak (in radians),  is the X-ray wave length 1.5406 Å, as well as 2θ is the Bragg angle (degree).The size of the typical crystallite was determined to be 24nm.

Field Emission Scanning Electron Microscope (FE-SEM)
The surface morphology of pure CuO nanoparticles that had been calcined at 400 °C was examined using FE-SEM.The prepared sample was produced as semi-spherical aggregates with a roughly uniform distribution, according to the SEM analysis.Equalsized produced nanoparticles' crystal nature is seen in Fig.The TEM image of CuO NPs is depicted in Fig. 3.
The TEM image of nanoparticles in various sizes and shapes is depicted in Fig. 3.The TEM examination aims to comprehend the crystalline properties of the nanoparticles.The particles are determined to be 28 nm in size and to be spherical in shape.The aggregation of tiny nanoparticles into larger ones that have dimensions that match those seen in the XRD study could be the cause of the larger particles 34 .

Energy-dispersive X-ray Spectroscope Characterization
The EDX spectrum of CuO NPs is depicted in Fig. 4. The spectrum has the usual copper and oxygen peaks.The outcomes support the great purity of the produced nanoparticles.Furthermore, the actual estimations derived from the EDX measurement concur with the theoretical computations of the elements.The matrix of the mixed catalyst has effectively dispersed the CuO NPs, as shown in Fig. 5.Additional information suggests typical x-ray mapping images that show the distribution of a CuO catalyst's elemental components and facilitate the dispersion of the catalyst's elements.The main objective of the adsorption analysis is to ascertain how the dye and adsorption interact in addition to compare the adsorption isotherm with the adsorption data.The Langmuir and Freundlich models were assessed in this study.The following formula [38][39][40] describes the linear Freundlich adsorption process as Eq.3: ) log( Ce) 3 The adsorption capacity, as well as intensity of adsorption, are shown by the Freundlich constants Kf and n, respectively are depicted in Fig. 6.
Calculating kf is done using the intercept, while n is done using the slope.For the CuO isotherm Freundlich, 1/n was determined in this work to be 0.235.Thus, this investigation supported the benefit of physical adsorption 41 .The adsorption is better fit by the Freundlich isotherm model (R2=0.9785).The data fits the Langmuir adsorption isotherm (Fig. 7), as can be seen in the Eq. 4, that follows 34,40,41 : The maximum capacity of Cibacron red dye is q max (mg/g), whereas the Langmuir constant is KL (mg/L).
The Langmuir isotherm's key characteristics are outlined and shown by the separation factor, sometimes referred to this as the dimensionless constant (RL) in Eq. 5 40 : The dye adsorbs best on CuO when the initial dye concentration is Ci (mg / L), and the RL values are all within the range of (0-1).

Effect of Adsorbent Mass
To test the effectiveness of the adsorbent, different masses of CuO NPs 0.005g, 0.01g, 0.05g, 0.1g, and 0.15g were introduced to 50 ppm of dye.Shaking the mixture at 298 K and 200 rpm took place.The relationship between removal percentage and mass is seen in the graph.Because there are more active sites in nanoparticles, adsorption happens very quickly.Fig. 9, demonstrates the increase in dye adsorption.by boosting the bulk of the CuO NPs.Ke is an equilibrium constant, R is gas constant is 8.314 J/mol K, and T is the temperature in Kelvin (K).According to a van't Hoff plot between ln K and 1/T in Fig. 10, the interaction was endothermic and the ∆H was 7.69 kJ/mole determent by slope.
The ∆S from the intercept, which was 24.38 J/mole, indicating that the adsorbed particles were still moving close to the surface.With a positive ∆G value of 0.538 KJ/mol at 293 K, non-spontaneous adsorption is implied.

Dynamics
Adsorbent applications depend on the kinetics of dye adsorption on CuO NPs' surface adsorbents.The dye analysis discovered that for 0.01 g of the CuO nanoparticle adsorbents, the adsorption equilibrium period was approximately 35 minutes.Additionally, in this research, the following information about adsorption was depicted using classical and kinetic models: Model of pseudo-first-order as Eq. 9 34,[40][41][42][43][44] : The equilibrium adsorption capacity, qe (mg g -1 ), the amount of dye that has been adsorbed after time, qt (mg g -1 ), and k1 is a pseudo-first-order rate constant (min -1 ), are shown in Fig. 11.The pseudosecond-order kinetic model is as Eq. 10 31,32 :

Conclusion
Green synthesis and imaging with XRD, SEM/EDX, and TEM were used to create highquality CuO.According to TEM studies, CuO NPs' particle size ranged from 28 nm.For removing dye from aqueous solutions, the observed adsorption properties are perfect.In both kinetic and thermodynamic experiments, the usefulness of CuO NPs as adsorbers was proven.Langmuir and Freundlich isotherm isotherm models were wellsuited to the data.Much better describes the adsorption is the Freundlich isotherm model.The adsorption is non-spontaneous and endothermic, according to thermodynamics.The slope of the van't Hoff plot was used to determine the enthalpy value (7.69 kJ/mole), which represents the physical

Figure 2 .
Figure 2. SEM images of the CuO NPs Transmission Electron Microscopy (TEM)

Figure 3 .
Figure 3. a)TEM images of the CuO NPs and b) distribution of nanoparticles

Figure 8 .
Figure 8.Effect of time on the cibacron dye adsorption onto the CuO NPs.

Figure 11 .
Figure 11.Dynamic of adsorption of dye pseudo-first-orderK2 is the second-order rate constant.The pseudosecond-order model may adequately describe the

Figure 12 .
Figure 12.Dynamic of adsorption of dye pseudo-second-order.