ABSTRACT
The degradation of synthetic organic dyes through photocatalysis requires structured nanoparticles (NPs). Copper oxide (CuO) NPs were used as the newest developed catalyst for the organic dye degradation under the irradiation of sunlight: The metal oxide NPs were synthesized using the fruit extract of Diplocyclos palmatus (L) C. Jeffrey. UV–visible light spectra showed an absorption band for CuO NPs at 277 nm. X-ray diffraction confirmed the monoclinic phase of CuO NPs. Scanning electron microscopy confirmed rod-shaped stacked particles. Energy-dispersive X-ray spectra indicating the presence of Cu in oxide form. For the degradation of methylene blue dye (MB), CuO NPs were used as photocatalyst for dye degradation under sunlight irradiation. This study confirmed the effects, such as irradiation time, concentration, pH, and catalyst dosage. The CuO NPs showed high photocatalytic degradation, degrading 90% of the dye in 120 min. The increased degradation of dye was observed on exposure to longer irradiation time. The increased concentration of dye resulted in a decreased rate of photodegradation. 95% degradation achieved at pH 9 showing that the pH medium also enhances the degradation. A higher dye degradation percentage was achieved by increasing the higher catalyst dosage of 0.013 g degraded 93% of dye. Thus in the treatment of wastewater containing pollutants, the synthesized CuO NPs acted as an efficient photocatalyst.
HIGHLIGHTS
The latest development for the removal of organic pollutants is of significant concern.
The dye degradation is affected by the catalyst amount, surface area, and size.
The CuO nanoparticles from the fruit extract of palmatus exhibited an advanced oxidation process that degrades pollutants with higher concentrations.
Photocatalytic methods are discussed.
This can be used for more efficient wastewater remediation in the future.
INTRODUCTION
In the wake of worldwide populations and industrial sectors, water resources have increased to epidemic levels due to various pollutants. This contagion pollutant causes a serious threat to water sources, resulting in the scarcity of water and affecting the quality of water. Therefore, it is necessary to prevail over the problems that protect the water supply, human health, and environment (Amdeha 2021; Mostafa & Amdeha 2022). Water pollution is an important problem arising. The main cause of pollution is the release of hazardous, toxic, and non-degradable (Qiu et al. 2008) dyes from industrial sectors. Organic dyes are an important cause of water pollution. These organic dyes not only affect the process of photosynthesis but also the health of living beings through skin irritation, allergies, and even cancer (Royer et al. 2010).
Moreover, 10–15% of dyes released into water resources are in the form of effluents from the textiles during the process of dyeing. Methods like biological and physicochemical processes have been used to treat the dyed water (Kumar et al. 2011; Mahmoodi et al. 2011; Singh & Dhaliwal 2020). These methods are sometimes found to be unsustainable for the environment. The development of nanotechnology created a possibility for the treatment of wastewater. Copper oxide nanoparticles (CuO NPs) are found to be effective. The intrinsic properties found in the CuO NPs are greatly suitable for the photocatalytic degradation process (Nagar & Devra 2019).
Organic molecules contained in the contagion wastewater are broken down by the technique of photocatalytic dye degradation, which releases hydroxyl (•OH), radicals using the necessary catalyst and radiation. The toxic compounds present in the water pollutants are converted into environmentally safe end products such as H2O and CO2 through these radicals (Kamat 2012; Hammad et al. 2018). Compared with other conventional processes, photocatalytic degradation is extensively used. Photocatalytic degradation can be applied to main stream activity due to its outstanding sustainability, low price, greater effectiveness, and lower pollution (Kumar et al. 2014).
Under temperate and suitable environmental conditions, the photocatalytic process undergoes excellent dye degradation and converts to hazardous minerals (Zhao et al. 2023). Thus, the degradation of synthetic organic dyes can be achieved (Velusamy & Lakshmi 2017). The most commonly used photocatalysts are metal and metal oxide NPs because of their distinct properties with a size of less than 100 nm. Methylene blue (MB) is used in paper, wool, silk, and cotton as a synthetic dye (Khodaie et al. 2013). In cosmetics, pharmaceuticals, and food colors, those dyes are also used. Unlike polluted water, MB is used in therapeutic fields (Dardouri & Sghaier 2017).
The present work involves the synthesis of CuO NPs from the fruit extracts of Diplocyclos palmatus (L) C. Jeffrey (D. palmatus) (Gautam et al. 2013) as a photocatalyst through the co-precipitation method, to improve the efficacy of the degradation of synthetic organic dyes. Plants are used because of their availability, less toxic nature, and capping behavior. Among metals, CuO NPs are used because of their unique properties. UV–visible light spectra, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) had been used to study the catalyst's characteristics. The aim of the work is to synthesize a cost-effective and efficient photocatalyst for MB dye degradation. The parameters that affect the dye degradation include pH medium, time, dosage of the photocatalyst, and dye concentration. On studying this aspect, it is much needed to optimize the degradation of synthetic organic dyes.
MATERIAL AND METHODS
Materials and chemicals
The chemicals copper sulfate pentahydrate (CuSO4·5H2O) and sodium hydroxide (NaOH) were purchased from Merck. From Sathyamangalam in the Tamil Nadu district of Erode, fruits of D. palmatus were gathered.
Preparation of fruit extracts
The fruits were washed three or four times with distilled water and dried for 40 days. The dried fruits were crushed and processed into powder. The powder weighed 25 g, and 250 mL of distilled water was added. The mixture was stirred using a magnetic stirrer for 2 h. The solution was then filtered using Whatman filter paper No. 1 and stored for further nanoparticle synthesis.
Synthesis of CuO NPs
Plant-mediated green synthesis has been used to produce CuO NPs, in which different functional groups found in fruits act as reducing agents, culminating in the formation of NPs. In a beaker, 25 ml of fruit extract was added, followed by 30 ml of 1 M aqueous CuSO4·5H2O. The mixture was then placed on a magnetic stirrer for 1 h, after which NaOH was added drop by drop, and a color change was observed. The resultant extract solution was centrifuged at 7,000 rpm for 20 min, and its supernatant was discarded. The resulting pellet containing CuO NP precipitate was collected and rinsed with distilled water to remove contaminants before being transferred to a China dish. The precipitate was dried in an oven at 70 °C. The dried fine powder was used for characterization.
Photodegradation of MB dye using CuO NPs
The breakdown of MB dye under UV irradiation was investigated using CuO NPs (Jassim et al. 2016). In a standard flask, approximately 0.0025 g of MB dye was mixed with 250 ml of distilled water. Various ppm dye solutions (10, 20, 30, and 40 ppm) have been produced. Each beaker holding 100 ml of (10 ppm) MB dye solution had 0.005 g of CuO NPs added separately (Dulta et al. 2022; Aroob et al. 2023). They were placed in the dark for approximately 30 min to achieve adsorption–desorption equilibrium. The mixtures were then exposed to sunlight for an assortment of time periods. The degradation of MB dye has been examined using a UV–visible spectrophotometer.
The study examines the effects of catalyst dosage, length of time, dye concentration, and pH medium on the photocatalytic degradation of MB. Different quantities of catalyst were employed to investigate the catalyst dose. The pH medium was tested using varied pH solution concentrations of 5, 7, and 9 to determine the impact of pH on MB dye degradation. Before synthesizing the dye solution, 1M HCl and 1M NaOH solutions were added to distilled water to create acidic and basic solutions. Different time intervals (5, 15, 30, 45, 60, 75, 90, 105, and 120 min) were investigated. Similarly, different dye concentrations of 10, 20, 30, and 40 ppm are investigated for the photocatalytic degradation of MB dye.
Dye degradation UV–visible analysis
Characterization
The synthesized CuO NPs from D. palmatus fruit extracts were characterized using a UV–visible spectrophotometer, X-ray diffraction (XRD), SEM, and EDX analysis. The absorption spectra of CuO NPs have been studied using UV–visible spectroscopy. A scanning electron microscope (Carl Zeiss USA-Model-Sigma with Gemini Column) was used to examine the particle size and surface morphology of the produced CuO NPs. The elemental composition of NPs was studied using EDX investigations.
RESULTS AND DISCUSSION
UV–visible analysis
XRD analysis
In this equation, D represents particle size, K is a shape factor (approximately equal to 0.9), λ is its X-ray wavelength (1.5418 A° with Cu K radiation), β is the full line width at half-maximum (FWHM) of the primary intensity peak, and θ is the Bragg's angle. The average particle size for the synthesized CuO NPs is 22 nm.
SEM and EDX analysis
Mechanism for photodegradation of MB dye using CuO NPs from D. palmatus fruit extract
The difference in energy between the oxidation and reduction processes is determined by the material band gaps. The photocatalytic degradation of metals is determined by their band gaps. A narrower band gap indicates greater photocatalytic dye degradation activity.
Effect of dye concentration of CuO NPs on the photocatalytic degradation
Effect of time of CuO NPs on the photocatalytic degradation
Effect of pH concentration of CuO NPs on photocatalytic degradation
Effect of catalyst dosage on photocatalytic degradation
Photocatalyst dosages . | Ratio of catalyst to dye . | Ratio . | % degradation . |
---|---|---|---|
0.005 | 10:5 | 2.1 | 55 |
0.007 | 14:7 | 61 | |
0.009 | 18:9 | 72 | |
0.011 | 22:11 | 84 | |
0.013 | 26:13 | 93 |
Photocatalyst dosages . | Ratio of catalyst to dye . | Ratio . | % degradation . |
---|---|---|---|
0.005 | 10:5 | 2.1 | 55 |
0.007 | 14:7 | 61 | |
0.009 | 18:9 | 72 | |
0.011 | 22:11 | 84 | |
0.013 | 26:13 | 93 |
CONCLUSION
CuO NPs synthesized from D. palmatus fruit extracts demonstrated high photocatalytic activity in the degradation of MB organic dye. After 120 min, 90% of the dye had been destroyed. Longer irradiation times lead to increased dye degradation. Furthermore, the degradation of MB dye was improved by employing a larger amount of catalyst; with 93% degradation achieved using 0.013 g of photocatalyst over 120 min. Conversely, larger dye concentrations resulted in lower photocatalytic degradation activity. 95% of the dye was destroyed in just 120 min at pH 9, demonstrating that increasing the pH of the medium enhances organic dye degradation.
DATA AVAILABILITY STATEMENT
All relevant data are included in the paper or its Supplementary Information.
CONFLICT OF INTEREST
The authors declare there is no conflict.