1 Introduction

Nanocomposites containing metal oxides are currently a significant research topic due to their high efficiency in features of sustainable development, the lack of secondary contamination during water treatment, and photocatalytic degradation [1,2,3]. Wastewater, which contains large quantities of harmful pollutants for the environment, is of particular research interest. Due to their high reactivity, vast surface area, functionalization, and effectiveness, nanoparticles are employed for the treatment and purification of wastewater [4,5,6]. Among the methods used to treat water, adsorption is considered effective because of its low cost, high efficiency, and effectiveness [7,8,9,10]. Wastewater cannot be sufficiently treated using conventional water treatment methods such as coagulation, flocculation, bed filtration, membrane filtration, precipitation, biodegradation, and oxidation [11,12,13,14]. Adsorption has been shown to be preferable to several other procedures since it is straightforward, impervious to dangerous pollutants, and adaptable [15,16,17]. Industries such as petrochemicals, paper, pulp, food, and textiles produce many different types of sanitary waste. Among the pollutants of concern are organic dyes, including Toluidine blue (TB), p-toluidine (PT), and m-Toluidine (MT), which are commonly found in industrial wastewater effluents [18, 19]. These dyes are used extensively in industries such as textiles, pharmaceuticals, and petrochemicals, but their improper disposal poses significant environmental risks [20]. TB, PT, and MT are known to be persistent and hazardous pollutants, often requiring advanced treatment methods for effective removal. Conventional water treatment processes may fall short in adequately treating these complex organic compounds. Hence, the development of advanced materials like our ZnO/CuO/Fe2O3 nanocomposite holds substantial promise in addressing the challenges posed by these recalcitrant dye pollutants.

Nanoparticle synthesis can generally be achieved using two primary approaches: physical methods or chemical and biological methods. Nevertheless, employing physical and chemical techniques for nanoparticle synthesis comes with certain disadvantages, including high expenses, toxicity, and environmental hazards [21]. Consequently, scientists have been exploring the potential of biological methods for producing nanoparticles. Biogenic sources, such as plants, actinomycetes, microorganisms, fungi, and algae, have been employed in the biological production of nanoparticles [22]. Recent research has suggested that plant extracts offer a promising environmentally friendly alternative for nanomaterial production [23,24,25,26,27,28]. The active components found in plant extracts, such as enzymes, polyphenols, phenolics, carbohydrates, and proteins, are effective in reducing, stabilizing, and encapsulating metal ions, leading to the creation of metal nanoparticles [29, 30]. Furthermore, nanoparticles generated from plants exhibit superior stability and consistency in terms of shape and size when compared to traditional chemical techniques [31]. In this context, the use of natural extracts as reducing and stabilizing agents in nanocomposite synthesis has emerged as an innovative and eco-conscious approach. Among the various plant extracts, the Ocimum Basilicum, or basil, extract holds particular promise. Ocimum Basilicum is renowned for its rich phytochemical composition, containing a wealth of bioactive compounds that can facilitate the reduction and capping of metal ions during nanocomposite synthesis [29]. Furthermore, its availability and ease of extraction make it an attractive candidate for sustainable materials production [32,33,34]. In this study, we harness the potential of Ocimum Basilicum leaf extract to synthesize a biogenic ZnO/CuO/Fe2O3 nanocomposite, highlighting the importance of green synthesis and the unique properties of this botanical agent in advancing nanomaterials for various applications.

Zinc oxide (ZnO) is an active and interesting material in photocatalytic applications, and it has been extensively studied due to its diverse physical and chemical properties [35,36,37]. In the field of photocatalytic processes, zinc oxide has emerged as a primary candidate due to its unique characteristics, such as low cost, easy accessibility to raw materials, non-toxicity, and good thermal and chemical stability [38]. The reported photocatalytic activity, however, may be greatly influenced by the shape and size of the used zinc oxide nanostructures [39, 40]. It is well known that low-dimensional zinc oxide structures, such as one-dimensional structures, have large surfaces, efficient carrier migration, and short charge carrier migration paths, all of which increase the photocatalytic activity [41, 42]. In other words, the characteristics and possible uses of low-dimensional zinc oxide nanocrystals can be determined by their carefully regulated composition and the precisely specified shape of various exposed crystal faces (i.e., polar and non-polar faces with variable energies on the surface) [43, 44].

The commercial use of zinc oxide in solar photocatalysis still has a number of limitations, including the broad bandgap, fast recombination of the photo-generated charge carrier, and the catalyst's corrosion and dissolution under harsh acidic conditions [45]. These problems can be resolved either by utilizing porous support materials to enhance the surface area by forming internal spaces for mass transfer or by combining zinc oxide with the other metal oxides to reduce the rate of recombination of photo-generated electrons and holes [46,47,48]. To address these problems, techniques have been reported, such as coupling with other photocatalysts, surface modification, ion, doping, dye improvement, integration into porous materials, and metal or non-metal doping, as the most effective approaches in the literature [49, 50]. Among these methods, the combination of zinc oxide with narrow bandgap semiconductors such as Fe2O3, CoFe2O4, WO3, CuS, In2O3, Bi2O3, g-C3N4, Fe3O4, and CuO can enhance the photocatalytic activity of zinc oxide by reducing the recombination of light-induced charge carriers [51].

Therefore, this study addresses the critical need for the development of advanced composite materials by exploring the novel approach of combining multiple functional composites. The aim is to enhance their properties and unlock new possibilities for various applications. In this research, we present a groundbreaking method for synthesizing a biogenic ZnO/CuO/Fe2O3 nanocomposite using an aqueous leaf extract of Ocimum Basilicum L. This innovative synthesis approach offers several advantages, including its environmentally friendly nature, sustainability, and avoidance of hazardous chemicals. The synthesized ZnO/CuO/Fe2O3 nanocomposite underwent a comprehensive characterization process, including UV–Visible spectrophotometry, SEM analysis, and XRD analysis, providing valuable insights into its optical properties, nanoscale size, morphology, and crystal structures. The combination of multiple functional composites in this nanocomposite offers exciting prospects for enhanced performance and diverse applications. The findings of this research hold significant importance for advancing composite materials and their utilization in various fields, including environmental remediation and multiple industries.

2 Materials and Methods

2.1 Materials

Ocimum Basilicum L. were collected from east Algeria. Iron (III) chloride (FeCl3, 98%), zinc chloride (ZnCl2, 98%), copper (II) chloride hydrate (CuCl2-2H2O, 98%), sodium hydroxide (NaOH, 98%), were purchased from Sigma-Aldrich, Germany.

2.2 Preparation of the Extract

The plant extract was prepared by collecting leaves of the Ocimum Basilicum plant. The leaves were cleaned using tap water to remove any dirt particles, followed by multiple washes with distilled water. A total of 200 g of the cleaned leaves was weighed and placed in a glass beaker with 1000 mL of distilled water. The mixture was left to sit overnight. The next day, the extract was filtered to remove any solid residues and transferred to a bottle. Finally, the bottle containing the extract was stored at a low temperature to ensure its quality and stability.

2.3 Synthesis of ZnO/CuO/Fe2O3 Nanocomposites by Green Method

To synthesize the ZnO/CuO/Fe2O3 nanocomposites, a mixture containing 8.2 g of FeCl3, 2.8 g of ZnCl2, and 8.2 g of CuCl2·2H2O was combined with the prepared Ocimum Basilicum extract. The resulting mixture was subjected to continuous stirring and heating at 75 °C for approximately three hours. During this process, drops of NaOH (2 M) were added incrementally to adjust the solution's acidity until a noticeable change in color occurred, leading to the formation of a brown precipitate. To separate the precipitate, a centrifuge was employed, operating at a speed of 3000 rpm for a duration of 5 min. The obtained precipitate was then subjected to multiple washes using distilled water (DW) to eliminate impurities. Subsequently, the wet powder was dried by placing it in an oven set at 80 °C overnight. To obtain the final ZnO/CuO/Fe2O3 nanocomposite, the dried powder underwent annealing in an oven at a temperature of 500 °C for a duration of 3 h. This process facilitated the formation and stabilization of the desired nanocomposite structure. The experimental procedure for preparing the ZnO/CuO/Fe2O3 nanocomposite.

2.4 Characterization ZnO/CuO/Fe2O3 Nanocomposite

The UV–visible spectrophotometer (SECOMAM, model 9600, France) was employed to assess the optical properties within the wavelength range of 200–800 nm. To investigate the crystalline nature of the ZnO/CuO/Fe2O3 nanocomposite, XRD analysis was performed using the Proto Manufacturing Company's Benchtop model XRD machine (USA). The Fourier transform infrared spectroscopy (FTIR) technique was utilized (Thermo Fisher Scientific, Nicolet iS5 model, USA) to confirm the functional groups present in the nanocomposites. Additionally, a scanning electron microscope (TESCAN, VEGA3 model, USA) was utilized to examine the particle size and shape. The crystallite size was determined using the Scherrer formula (Eq. 1), where a prominent peak with the highest intensity was selected. The formula is as follows [52]:

$$D = \frac{k \lambda }{{\beta \cos \theta }}$$
(1)

Here "k" represents the form factor (0.9), "D" represents the crystallite size (0.15418 nm, CuK), "β" denotes the Full Width at Half Maximum (FWHM), and "θ" represents the diffraction angle.

2.5 Photocatalytic Activity of ZnO/CuO/Fe2O3 Nanocomposite

The degradation of Toluidine blue (TB), p-toluidine (PT) and m-Toluidine (MT) under sunlight at 29 °C, was studied using the nanocomposite as a photocatalyst. An aqueous solution containing the dyes at a concentration of 2.5 × 10–5 M of TB, p-toluidine and m-Toluidine was used. 5 ml of each dye was placed separately in several beakers and 5 mg of ZnO/CuO/Fe2O3 was added. The resulting mixture was then irradiated under sunlight for 0, 15, 30, 45, 60, 75, 90 and 105 min. ZnO/CuO/Fe2O3 was separated from the solution using a photocatalyst powder removal centrifuge. The degradation activity was investigated in March 2023 and the average sunlight intensity was about 29 °C in El Oued, Algeria. The absorbance of dye was analyzed through UV–Vis spectrophotometry in the range of 200–900 nm. The percentage of hydrolysis of each dye was calculated using the following equation [53].

$$\% degradation = \frac{{A_{0} - A_{\left( t \right)} }}{{A_{0} }} \times { }100$$
(2)

where \({A}_{0}\) is the measured absorbance of dye solutions without the catalyst nanocomposite, \({A}_{(t)}\) is the measured absorbance when the catalyst is added after each time periods.

3 Results and Discussion

3.1 Optical Characteristics and Band Gap Energy

Figure 1 illustrates the UV–Vis absorption spectra of the ZnO/CuO/Fe2O3 nanocomposite, providing valuable insights into its optical properties.

Fig. 1
figure 1

a UV–Vis absorption spectra of ZnO/CuO/Fe2O3 NC, b Energy dependence of (αhv)2 for ZnO/CuO/Fe2O3 NC

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In Fig. 1a, the absorption spectrum in the visible range reveals a peak at λmax = 360.9 nm. This indicates that the nanocomposite is capable of absorbing light in the visible region, suggesting its potential for various optoelectronic applications. Furthermore, the band gap energy of the ZnO/CuO/Fe2O3 nanocomposite was determined using the (αhν)2 versus energy function (eV) plot, as shown in Fig. 1b. By analyzing the data, the band gap energy was estimated to be 1.44 eV. The band gap energy is a crucial parameter in determining the semiconductor behavior and optical properties of materials. The obtained value of 1.44 eV indicates that the nanocomposite possesses a suitable band gap for absorbing light in the visible range. The successful synthesis of the ZnO/CuO/Fe2O3 nanocomposite is supported by the observed absorption in the visible spectrum and the determined band gap energy. These findings highlight the potential of the nanocomposite for applications such as photocatalysis, photovoltaics, and sensor technologies, where efficient light absorption and charge carrier generation are essential.

3.2 XRD Analysis

As shown in Fig. 2, the XRD pattern showed multiple peaks of the produced ZnO/CuO/Fe2O3 NC.

Fig. 2
figure 2

XRD patterns of ZnO/CuO/Fe2O3 NC

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The broad peaks show that the material as it was produced comprises nanoscale-sized particles. The 2θ angles corresponding to the diffraction peaks are as follows: 31.779°, 34.430°, 36.265°, 47.554°, 56.615°, 62.876°, 66.400°, 67.971°, 69.112°, 72.587°, and 76.988°. These angles correspond to the crystallographic planes (1 0 0), (0 0 2), (1 0 1), (1 0 2), (1 1 0), (1 0 3), (2 0 0), (1 1 2), (2 0 1), (0 0 4), and (2 0 2), respectively. These observations indicate that the ZnO NPs possess a hexagonal crystal structure with a space group of P63mc (186) and lattice parameters of a = 3.2495 Å and c = 5.2069 Å, as specified in JCDPS Card No. 01-089-0510. Additionally, the presence of the CuO NPs was confirmed by the XRD spectrum, which included peaks other than the normal ZnO/CuO/Fe2O3 peaks at 2θ = 32,524°, 35,564°, 38,725°, 46,287°, 48,795°, 51,360°, 53,480°, 56,719°, 58,297°, 61,582°, 65,816°, 66,528°, 68,120°, 68,923°, 72,424°, 72,963°, 75,032°, corresponding to crystallographic reflection planes (1 1 0), (−1 1 1), (1 1 1), (−1 1 2), (−2 0 2), (1 1 2), (0 2 0), (0 2 1), (2 0 2), (−1 1 3), (0 2 2), (3 1 0), (2 2 0), (−2 2 1), (3 1 1), (2 2 1) and (0 0 4) respectively, where CuO NPs had a monoclinic crystal structure (Space group C2/c (15) and lattice parameters of a = 4,6830 Å b = 3,4240 Å and c = 5,1290 Å) JCDPS Card No. 01-089-5896. Furthermore, the XRD spectrum revealed peaks other than the typical Fe2O3 peaks, confirming the presence of the ZnO/CuO/Fe2O3 complex at 2θ = 23,851°, 32,856°, 35,080°, 39,076°, 40,321°, 42,866°, 48,823°, 53,511°, 55,254°, 56,544°, 57,194°, 61,527°, 62,931°, 65,114°, 68,891°, 71,636°, and 74,133°, corresponding to crystallographic reflection planes (0 1 2), (1 0 4), (1 1 0), (0 0 6), (1 1 3), (2 0 2), (0 2 4), (1 1 6), (2 1 1), (1 2 2), (0 1 8), (2 1 4), (3 0 0), (1 2 5), (2 0 8), (1 1 9), (2 2 0) respectively, where Fe2O3 NPs had a rhombohedral crystal structure (Space group R-3c (167) and lattice parameters of a = 5,1120 Å b = 5,1120 Å and c = 13,8200 Å) JCDPS Card No. 088-2359. The crystallite sizes of the ZnO/CuO/Fe2O3 nanocomposite sample were 29.1 nm, according to the Scherrer formula.

3.3 FTIR Analysis

The FT-IR studies of Ocimum Basilicum leaf extract and synthesized ZnO/CuO/Fe2O3 nanocomposite are given in Fig. 3.

Fig. 3
figure 3

FTIR spectra of ZnO/CuO/Fe2O3 NC (red) and Ocimum Basilicum extract (blue)

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The FTIR analysis was performed to determine the purity and nature of the nanoparticles, as well as the existence of phytochemicals in the extract. The FTIR spectrum at around 3400–3800 cm−1 for the Ocimum Basilicum extract could be attributed to the hydroxyl of the phenols stretching mode [54]. The O–H stretching vibrations could potentially account for the absorption peaks detected within the range of 3200–3500 cm−1 in the spectrum of the ZnO/CuO/Fe2O3 nanocomposite [55]. The peaks around 2360 cm−1 and 3073 cm−1 are the H–O–H vibration of a cluster of crystallized water molecules and C–H stretching, respectively [56, 57]. The peak at 1508 cm−1 was likely due to C=O [57]. The stretching vibration of C–O–C is responsible for the band observed at 1100 cm−1 in both extract and ZnO/CuO/Fe2O3 nanocomposite spectrum. Furthermore, the peaks detected at 2878 cm−1 were assigned to the stretching vibrations of the –CH2 functional group [58]. According to related studies, the characteristic peaks of Fe–O in Fe2O3 were at 390–566 cm−1, while the Cu–O stretching band in the monoclinic phase and the Zn–O stretching band were observed in 420–600 and 401–670 cm−1 regions, respectively [59,60,61].

3.4 Structure and Morphology

The morphological dimensions of the produced ZnO/CuO/Fe2O3 nanocomposites were investigated using SEM images (Fig. 4a).

Fig. 4
figure 4

SEM images of bio-synthesized ZnO/CuO/Fe2O3 nanocomposite. a Representative SEM image showing the morphology of the nanocomposite. b Size distribution analysis providing information about the particle size distribution. c EDX result and elemental analysis highlighting the presence of different elements in the nanocomposite

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The average size distribution of the biosynthesized ZnO/CuO/Fe2O3 nanocomposite is around 65 nm, as shown by the particles size distribution histograms in Fig. 4b. As shown, ZnO/CuO/Fe2O3 nanocomposite particles come in a variety of sizes and irregular forms. The performance of photocatalysis can be significantly influenced by the geometry of a material's surface. Figure 4c illustrates the EDX analysis of the ternary nanocomposite ZnO/CuO/Fe2O3, displaying the mass and atomic percentages of different elements. The embedded table summarizes these value percentages for easy reference. The higher mass and atomic percentages of oxygen (O) and zinc (Zn) indicate their dominant presence in the composition. This could be attributed to the synthesis method, or the nature of the starting materials used. Conversely, iron (Fe), copper (Cu), and chlorine (Cl) exhibit lower percentages in comparison. These findings provide insights into the elemental compositions of the nanocomposite. Figure 4c enhances the understanding of the composition by visually representing the higher percentages of oxygen (O) and zinc (Zn), as well as the lower percentages of iron (Fe), copper (Cu), and chlorine (Cl). This graphical overview complements the table, facilitating comparisons between different elements and contributing to a comprehensive understanding of the nanocomposite's composition.

3.5 Photocatalytic Activity Study

After the obtained results, this study confirmed the effectiveness of the nanocomposite in adsorption and photocatalysis in the decomposition of toluidine blue (TB), p-toluidine (PT) and m-Toluidine (MT) dyes under sunlight at normal atmospheric temperature. The intensity of the absorption peaks for all dyes used in this experiment decreased gradually with the increase in time without changing the maximum absorption wavelength. UV–Vis analysis revealed the absorption features at λmax = 630.8 nm, 287.2 nm and 283 nm for TB, PT and MT, respectively. The results indicate that ZnO/CuO/Fe2O3 NPs have good disappearance efficacy TB, PT and MT dyes and showed a degradation rate of 99%, 99.1% and 99.7%, within 90 min, respectively (Fig. 5a, b, and e).

Fig. 5
figure 5

Photodegradation efficiency versus reaction time: UV–vis spectra for the degradation of a MT dye, c PT dye, and e TB dye using ZnO/CuO/Fe2O3 NC. The degradation rate of b MT dye, d PT dye, and f TB dye using ZnO/CuO/Fe2O3 NC

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Kinetic studies, using a pseudo-first-order kinetic model, demonstrate the photocatalytic performance of the as-prepared photocatalysts (Eq. 3) [62] as shown in Fig. 5. Moreover, the rate constant of ZnO/CuO/Fe2O3 NC was estimated to be about 0.0314 min−1, 0.0189 min −1 for TB, p-toluidine and m-Toluidine, respectively.

$$\ln \left( {\frac{Ct}{{C0}}} \right) = t \times k$$
(3)

where K is pseudo-first order rate constant, and t is irradiation time.

The photoremoval kinetics of the dyes was studied using pseudo-first-order kinetics. The degradation efficiency and rate constant for TB, p-toluidine and m-Toluidine were calculated from the reaction profiles and kinetic plots in Fig. 6 using the simple equations as follows:

$${\text{R\% }} = \left( {1 - \frac{{{\text{Ct}}}}{{{\text{C}}0}}} \right) \times 100$$
(4)

where R% is degradation efficiency of TB, p-toluidine and m-Toluidine, C0 is the initial concentration and Ct is the concentration of days at different irradiation time.

Fig. 6
figure 6

Shows the first-order kinetic plot of ln(A0/At) versus time for the degradation of MT, PT, and TB dyes using ZnO/CuO/Fe2O3 NC

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3.6 Reusability and Stability Performance of ZnO/CuO/Fe2O3 Photocatalyst

The objective of this study was to investigate the stability and reusability of the ZnO/CuO/Fe2O3 nanocomposites, which was prepared for treating textile wastewater. This research also aimed to assess the applicability of the nanocomposite in industrial settings, considering sustainability and stability as important factors. In the initial cycle, a sample of the synthesized photocatalyst (20 mg) was added to a solution containing TB dye (2.5 × 10–5 M) in a volume of 20 mL. Each solution was then exposed to sunlight for 105 min. Subsequently, the photocatalyst sample was separated from the solutions using filtration, washed multiple times with double distilled water, and dried in an oven at 60 ℃ for 4 h to remove any remaining moisture. The dried photocatalyst was reused in the subsequent cycles under the same experimental conditions as the first cycle. This process was repeated for five cycles, and the degradation efficiencies for each cycle, as well as the degradation percentages over time (C/C0), are presented in Fig. 7a and b.

Fig. 7
figure 7

a Recyclability of the ZnO/CuO/Fe2O3 photocatalyst for degradation of TB; b Reusability (degradation efficiency vs. number of cycles) of ZnO/CuO/Fe2O3 in the photodegradation of TB, respectively. c XRD analysis of ZnO/CuO/Fe2O3 and reused. The results demonstrated consistently high photocatalytic degradation efficiencies for the photocatalyst, indicating its excellent performance and comparability throughout the experiment. The X-ray diffraction (XRD) data depicted in Fig. 7c provide clear evidence that the crucial XRD diffraction peaks of the ZnO/CuO/Fe2O3 photocatalyst remained unaltered before and after the photodegradation process, even after undergoing five consecutive photocatalytic cycles. This observation signifies that the catalytic substance did not cause any changes in the diffraction peaks of the ZnO/CuO/Fe2O3 photocatalyst

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3.7 Photodegradation Mechanism of ZnO/CuO/Fe2O3

The degradation process of dyes in a solution is initiated by the catalyst's photoexcitation, which results in the generation of electron–hole pairs on the photocatalyst's surface (as shown in Eqs. 5–11) [63].

$${\text{ZnO/CuO/Fe}}_{{2}} {\text{O}}_{{3}} \mathop{\longrightarrow}\limits^{hv}e^{ - }_{{({\text{CB}})}} + h^{ + }_{{({\text{VB)}}}}$$
(5)
$$e^{ - }_{{({\text{CB}})}} \mathop{\longrightarrow}\limits^{{{\text{ZnO/CuO/Fe}}_{{2}} {\text{O}}_{{3}} }}{\text{o}}_{2}^{ \cdot - }$$
(6)
$$h^{ + }_{{({\text{VB}})}} + {\text{H}}_{{2}} {\text{O}}\mathop{\longrightarrow}\limits^{{{\text{ZnO/CuO/Fe}}_{{2}} {\text{O}}_{{3}} }}{\text{H}}^{ + } + {\text{OH}}^{ - }$$
(7)
$${\text{H}}^{ + } + {\text{O}}_{2}^{ \cdot - } \to {\text{HO}}_{2}^{ \cdot }$$
(8)
$${\text{HO}}_{2}^{ \cdot } + {\text{HO}}_{2}^{ \cdot } \to {\text{H}}_{{2}} {\text{O}}_{{2}} + {\text{O}}_{{2}}$$
(9)
$${\text{H}}_{{2}} {\text{O}}_{{2}} \mathop{\longrightarrow}\limits^{hv}{\text{2OH}}^{ \cdot }$$
(10)
$${\text{Dyes + OH}}^{ \cdot } \mathop{\longrightarrow}\limits^{{h^{ + } }}{\text{CO}}_{{2}} {\text{ + H}}_{{2}} {\text{O}}$$
(11)

The positively charged holes (h +) in the valence band (hVB +) possess a high oxidative potential, enabling the direct oxidation of dyes into reactive oxidative intermediates (as illustrated in Eq. (6)). The degradation of TB, for instance, involves the participation of OH• radicals, which are formed either by the decomposition of water or through the reaction of h + with OH − molecules, OH• radicals, although non-selective, are potent oxidants that facilitate the partial or complete mineralization of organic compounds. When ZnO/CuO/Fe2O3 nanocomposites are irradiated with visible light, they undergo photoexcitation via surface absorption, leading to the injection of photoexcited electrons into O2. As a result, the production of superoxide and hydroxyl radicals is accelerated, ultimately enhancing the rate of degradation for dye molecules. The process of photocatalytic degradation of dyes using ZnO/CuO/Fe2O3 nanocomposite under solar radiation is shown in the following equations [64]. Figure 8 illustrates the mechanism behind the enhanced photocatalytic activity of ZnO/CuO/Fe2O3 nanocomposites under solar irradiation.

Fig. 8
figure 8

Photocatalytic mechanism of ZnO/CuO/Fe2O3 NC

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4 Conclusion

In conclusion, this study successfully synthesized a biogenic ZnO/CuO/Fe2O3 nanocomposite using an aqueous leaf extract of Ocimum Basilicum L. The confirmation of biosynthesis was achieved through UV–Visible spectrophotometry, which provided evidence of ZnO/CuO/Fe2O3 NC formation. SEM analysis confirmed the nanoscale size of the nanocomposite, measuring at 65 nm. XRD analysis revealed the hexagonal structure of ZnO and monoclinic structure of CuO. FT-IR spectroscopy verified the presence of functional groups in the composite. The ZnO/CuO/Fe2O3 NC exhibited exceptional degradation capabilities for various dyes, achieving high degradation rates within a short reaction time. The degradation followed a pseudo-first order model, with rate constant values indicating efficient degradation. The nanocomposite also demonstrated excellent degradation reusability. These findings highlight the potential of the environmentally friendly ZnO/CuO/Fe2O3 nanocomposite for various applications in wastewater treatment and environmental remediation.