Trends Sci. 2025; 22(7): 9988

Photocatalytic Degradation of Congo Red Dye using ZnFe₂O₄/SnO₂ Composite with Response Surface Methodology (RSM) Optimization

Gierrald Abduh¹, Muhammad Said² and Poedji Loekitowati Hariani^2,*

¹Master Program in Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Sriwijaya,

Ogan Ilir 30662, Indonesia

²Research Group on Magnetic Materials, Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Sriwijaya, Ogan Ilir 30662, Indonesia

(^*Corresponding author’s e-mail: [email protected])

Received: 13 February 2025, Revised: 15 March 2025, Accepted: 22 March 2025, Published: 20 May 2024

Abstract

In this investigation, the synthesized ZnFe₂O₄/SnO₂ composites for the photocatalytic degradation of Congo red dye. Doping SnO₂ onto ZnFe₂O₄ optimized the energy gap, promoting light absorption in the visible spectrum. The ZnFe₂O₄/SnO₂ composites were analyzed using XRD, UV-DRS, SEM-EDS, VSM, and pHpzc. Photocatalytic degradation is optimized using Central Composite Design (CCD), which is based on response surface methodology (RSM). The XRD characterization results of the ZnFe₂O₄/SnO₂ composites demonstrate the success of the synthesis method. The composite has a combined 2θ of ZnFe₂O₄ and SnO₂, with a crystallite size of 17.50 nm. A band gap value of 2.46 eV indicates that the material can absorb most of the visible light spectrum. The EDS mapping results verify the presence of SnO₂ on the surface of ZnFe₂O₄, and the saturation magnetization value of 12.80 emu/g confirmed the composite’s magnetic properties. Degradation optimization using RSM indicated that the quadratic model effectively characterizes the photocatalytic degradation of Congo red dye. The RSM model’s high accuracy in predicting experimental outcomes is evidenced by the minor difference in efficiency degradation between experimental and predicted values, with an R² of 0.9851 and a p-value < 0.05. The optimum degradation efficiency was achieved at a solution pH of 4, a Congo red dye concentration of 10 mg/L, and an irradiation time of 80 min. The composite exhibits great stability, efficiency, and reliability; the reuse evaluation after 5 cycles indicated a deterioration reduction of less than 5 %.

Keywords: ZnFe₂O₄/SnO₂ composite, Degradation photocatalytic, Congo red dye, Optimization by RSM

Introduction

The rapid rate of population expansion, urbanization, and industrial development has heightened the demand for clean water [1,2]. Various sectors, including textiles, soap, cosmetics, paint, and paper, utilize dyes for coloration [3,4]. Inefficient operations in the textile industry led to around 10 - 20 % of dyes being discharged as liquid waste [5,6]. Liquid waste containing dyes is estimated to account for 20 % of global water contamination [6]. Humans and aquatic organisms are adversely affected by liquid waste that contains dyes. Dyes are stable chemicals that resist degradation; their presence in water can disrupt the

photosynthesis of aquatic plants and phytoplankton, which are fundamental to the aquatic food chain, hence diminishing the oxygen supply in water [7,8]. The toxicity of dyes varies by kind, but generally, they can induce health issues, including carcinogenicity, mutagenicity, and respiratory tract illnesses [9]. Approximately 60 - 70 % of global dye produced consists of azo dyes, which are characterized by the presence of 1 or more chromophore groups (-N=N-) in their molecular structure [10,11]. Congo red dye (C₃₂H₂₂N₆Na₂O₆S₂) is a commonly utilized industrial dye characterized by an aromatic ring and 2 azo groups.

The photocatalytic degradation approach for contaminant removal is frequently employed due to its efficiency, simplicity, and ability to transform toxins into simpler compounds without generating secondary pollutants [12]. The degradation process employs catalytic materials in conjunction with light sources, such ultraviolet, visible, or sunlight, to generate potent oxidative species [13]. Several metal oxides have been used for the photocatalytic degradation of dyes, including SnO₂ [14], TiO₂ [15], WO₃ [16], ZnO [17], CuO [18], and MnO₂ [19].

SnO₂ is an n-type semiconductor that is often used for the degradation of organic pollutants. Excellent chemical and thermal stability, non-toxicity, and low cost are the advantages of SnO₂ as a catalyst [20,21]. However, SnO₂ has a weakness, namely having a wide band gap of around 3.6 eV, suitable for absorbing light in the UV region, while sunlight only contains 5 % UV light. Another weakness is the high rate of electron-hole pair recombination, causing only a small portion of electrons and holes produced by light absorption to contribute to the catalytic reaction and separation process after being used for waste treatment [22,23]. To overcome these problems, several researchers have doped SnO₂ with several materials such as SnO₂-Cu [24], SnO₂/NiFe₂O₄ [23], Fe-SnO₂ [25], and Fe₃O₄-Ag/SnO₂ [26].

ZnFe₂O₄ is a ferrite compound with possible applications as a dopant for SnO₂. SnO₂ doped with ZnFe₂O₄ possesses a low band gap (~1.9 eV), enabling it to absorb light in the visible spectrum. UV and visible light can both be activated by ZnFe₂O₄. Moreover, ZnFe₂O₄ exhibits excellent chemical and thermal stability, is non-toxic, and possesses magnetic properties that enable the separation of catalysts from the reaction liquid via a magnetic attraction [27,28]. Recombination of electron-hole pairs is a prevalent issue in semiconductor photocatalysts. ZnFe₂O₄ can function as a superior center for charge carrier separation. Consequently, the amalgamation of ZnFe₂O₄ with SnO₂ constitutes a dependable approach to enhancing photocatalytic efficacy.

This research aims to carry out photocatalytic degradation of Congo red dye using ZnFe₂O₄/SnO₂ composites under visible radiation. Currently, a statistical approach to optimizing photocatalytic degradation is a method to maximize experimental efficiency and effectiveness. Response Surface Methodology (RSM) is an optimization modeling to analyze the influence between variables. This approach minimizes the number of experiments conducted, saving time and costs [29]. Through the combination of experiment and statistical optimization, this work offers novel and important insights into ZnFe₂O₄-SnO₂ composite for dye degradation since these contributions advance our understanding of wastewater treatment techniques. For ZnFe₂O₄/SnO₂ composite characterisation, XRD, SEM-EDS, UV-DRS, VSM, and pHpzc are employed. Optimization of photocatalytic degradation uses the RSM method with a Central Composite Design (CCD) design with the independent variables of pH, concentration and irradiation time.

Materials and methods

The chemicals used include Zn(NO₃)₃, Fe(NO₃)₃.9H₂O, CO(NH₂)₂, SnO₂, NaCl, HCl, NaOH, EDTA (Ethylenediaminetetraacetic acid), IPA (Isopropyl alcohol), BQ (Benzoquinone), and ethanol, which are analytical grade from Merck, Germany. Distilled water is used as a solvent.

Synthesis of ZnFe₂O₄

The synthesis of ZnFe₂O₄ was conducted by the solution combustion technique utilizing urea as the fuel source. A total of 1.72 g of Zn(NO₃)₃ and 6.70 g of Fe(NO₃)₃.9H₂O were poured into a 100 mL beaker glass, then 3.96 mL of CO(NH₂)₂ and 50 mL of distilled water were added. The mixture was agitated for 30 min with a magnetic stirrer and subsequently dried in an oven at 80 °C for 10 h. Subsequently, calcination was conducted at a temperature of 500 °C for 2 h. The resultant black powder gained is ZnFe₂O₄.

Synthesis of ZnFe₂O₄/SnO₂ composite

The synthesis of the ZnFe₂O₄/SnO₂ composite was conducted with a mass ratio of ZnFe₂O₄ to SnO₂ equal to 1:2. A total of 1 g of ZnFe₂O₄ and 2 g of SnO₂ were ground together, and 50 mL of distilled water was added, then sonicated using a sonicator of 500 W for 30 min. The resultant brownish precipitate is a ZnFe₂O₄/SnO₂ composite, isolated from the solution and subsequently baked in an oven at 80 °C for 10 h. The precipitate was calcined in solution at 500 °C for 3 h, with a heating rate of 4 °C/min.

Determination of pHpzc

pHpzc was determined following the methodology of Kumar et al. [30]. Zero point two g of ZnFe₂O₄/SnO₂ composite was introduced to multiple 100 mL conical flasks containing 50 mL of 0.1 M NaCl solution. The solution was modified to achieve a pH range of 2 to 12 with 0.1 M HCl and NaOH solutions. Additionally, agitation was performed with a shaker at a velocity of 120 rpm for 48 h. pHpzc was ascertained from the graph depicting initial pH against ΔpH (pH_final – pH_initial).

Characterization

A variety of techniques were employed for the characterization of ZnFe₂O₄ and ZnFe₂O₄/SnO₂ composites. Structural analysis was conducted using X-ray diffraction (XRD PANalycal) across the 2θ range of 10 - 90 °. Absorbance and band gap energy were assessed via Diffuse Reflectance Spectroscopy (DRS) utilizing a Cary 60 UV-Vis DRS apparatus. Material morphology, element composition, and element distribution were analyzed using a Scanning Electron Microscope (SEM) equipped with Dispersive Energy X-ray spectroscopy (EDS mapping) (SEM-EDS Hitachi Flexsem 100). The saturation magnetization was measured using a vibration sample magnetometer (VSM OXFORD 1.2 H) at a temperature of 298 K, within a magnetic field range of –18.0 to +18.0 kOe.

Design experiment by RSM

Response Surface Methodology (RSM) was employed in the experimental design utilizing Design Expert 13 software to optimize the degradation parameters. Central Composite Design (CCD) was used to investigate the correlation between independent factors and the response variable (degradation efficiency). The independent variables consist of solution pH (A), Congo red dye concentration (B), and irradiation time (C). A 300 W xenon lamp served as the irradiation source, positioned 15 cm from the sample. A total of 20 trials were conducted, each with 3 repetitions. A 50 mL solution of Congo red dye was prepared by incorporating 0.02 g of the ZnFe₂O₄/SnO₂ combination. The experiment configuration is detailed in Table 1. To establish an adsorption/desorption equilibrium, stirring was conducted in a dark environment for 30 min prior to the photocatalytic degradation process. The absorbance of the Congo red dye solution was quantified at a wavelength of 498 nm. The efficiency of deterioration was ascertained using the subsequent equation:

Where dan represent the initial and final concentration of Congo red dye.

Table 1 Independent value for CCD.

Results and discussion

Characterization of ZnFe₂O₄ and ZnFe₂O₄/SnO₂ composite

Figure 1 illustrates the diffraction peaks of ZnFe₂O₄ and the ZnFe₂O₄/SnO₂ composite. The ZnFe₂O₄ peak aligns with JCPDS card 22-1012, indicating a cubic spinel structure for ZnFe₂O₄ [31]. The spinel structure comprises Zn²⁺ cations typically residing in tetrahedral sites (A-site) and Fe³⁺ cations in octahedral sites (B-site) within the oxide lattice. The 2θ peaks observed at 18.30, 30.03, 35.42, 43.08, 53.11, 56.90, and 62.55 ° correspond to Miller indices (111), (220), (311), (400), (422), (511), and (440). The peak of the ZnFe₂O₄/SnO₂ composite comprises the combination of 2 distinct peaks: ZnFe₂O₄ and SnO₂. SnO₂ exhibits peaks at 2θ = 26.60, 34.04, 37.91, 51.76, 54.76, 64.73, and 65.88 °. According to JCPDS card No. 41-1445, the peaks that have been detected match the crystal planes (110), (101), (200), (211), (220), (112), and (301). The Scherrer equation is employed to ascertain crystallite size. The crystallite size of ZnFe₂O₄ is 21.23 nm, whereas the ZnFe₂O₄/SnO₂ composite exhibits a crystallite size of 17.50 nm. Doping SnO₂ with ZnFe₂O₄ leads to smaller crystal sizes because the interface or strain in the lattice limits their growth.

Figure 1 XRD pattern of (a) ZnFe₂O₄ and (b) ZnFe₂O₄/SnO₂ composite.

The SnO₂ peak in the UV-DRS spectra typically manifests in the ultraviolet range. The investigation conducted by Desouky et al. [23] determined the wavelength of SnO₂ to be 330 nm. The combination with NiFe₂O₄ induces a shift in the wavelength within the visible spectrum, approximately at 600 nm. This investigation suggests that the absorption peak of ZnFe₂O₄/SnO₂ occurs at 550 nm (Figure 2(a)). The band gap is an essential indicator that signifies the optical qualities and prospective applications of composites in photocatalysis. ZnFe₂O₄ is an n-type semiconductor with a low band gap (1.7 - 2.2 eV), whereas SnO₂ possesses a broad band gap (~3.6 eV) [25,32]. Charge transfer at the contact can diminish the energy necessary for electron excitation. The combined effect of ZnFe₂O₄ with SnO₂ can diminish the band gap of SnO₂. Figure 2(b) shows that the band gap of ZnFe₂O₄ is 1.98 eV, while that of the ZnFe₂O₄/SnO₂ combination is 2.46 eV. The findings align with other research, specifically indicating that the band gap value of ZnFe₂O₄ ranges from 1.89 to 1.92 eV when synthesized via the solution combustion method at temperatures between 400 and 1000 °C [27], whereas ZnFe₂O₄ synthesized through the laser ablation method exhibits a band gap between 2.17 and 2.27 eV [33].

Figure 2 (a) UV DRS absorption spectra and (b) Plot of (αhυ)² against hυ of ZnFe₂O₄ and ZnFe₂O₄/SnO₂ composite.

Figure 3 illustrates the morphology of ZnFe₂O₄ and ZnFe₂O₄/SnO₂ composites as observed through SEM investigation. The features of the ZnFe₂O₄/SnO₂ composite showed a reduction in the size of the fibrillar structure and sporadic breakdown in the fibrillar structure into individualised fibrils, whereas the composite was embedded with SnO₂. The EDS mapping results depicted in Figure 4 indicate that the composition of ZnFe₂O₄/SnO₂ comprises the elements O, Sn, Zn, and Fe. The presence of Sn signifies the successful synthesis of the ZnFe₂O₄/SnO₂ compound.

Figure 3 Morphology of (a) ZnFe₂O₄ and (b) ZnFe₂O₄/SnO₂ composite.

Figure 4 Elemental mapping of ZnFe₂O₄/SnO₂ composite.

The synthesis method and particle size influence the magnetic characteristics of ZnFe₂O₄. The ferrimagnetic characteristics of ZnFe₂O₄ arise from the perturbation of the arrangement of Fe³⁺ and Zn²⁺ ions at the tetrahedral (A) and octahedral (B) sites. This study determined the saturation magnetization (Ms) value of ZnFe₂O₄ to be 28.15 emu/g. The Ms value acquired in this investigation exceeded the findings of prior studies, specifically ± 10 emu/g [34] and 11.04 nm [35]. The ZnFe₂O₄/SnO₂ composite exhibits a Ms value of 12.80 emu/g. The reduction in the Ms value of the composite results from doping with SnO₂, which is diamagnetic. The investigation conducted by Chen et al. [36] revealed a similar occurrence, wherein the Ms value of ZnFe₂O₄, initially 44 emu/g, decreased to 11 emu/g upon doping with TiO₂. Despite the reduction in magnetic properties, the composite continues to exhibit robust magnetic characteristics (Figure 5).

Figure 5 Magnetization curves of (a) ZnFe₂O₄ and (b) ZnFe₂O₄/SnO₂ composite at room temperature.

The surface of a material can be positively or negatively charged depending on the pH of the solution. The pH of 0 charge (pHpzc) is the pH value on the surface of a material where the number of positive and negative charges adsorbed on the surface of the material is balanced. The pHpzc for the ZnFe₂O₄/SnO₂ composite is 6.70, indicating that at this pH, the material’s surface is neutral, and ions from the solution will not be significantly adsorbed. At a pH below 6.70, the ZnFe₂O₄/SnO₂ composite is likely to have a positive charge due to the adsorption of protons (H⁺) on its surface. Conversely, with a pH exceeding 6.70, this substance will acquire a negative charge owing to a reduction in H⁺ ion concentration and an elevation in OH⁻ ion concentration in the solution. This value closely aligns with other studies, specifically the pHpzc of the ZnFe₂O₄/Mn₂O₄ composite, which is 6.75. Figure 6 illustrates the pHpzc curve of the ZnFe₂O₄/SnO₂ composite.

Figure 6 pHpzc of ZnFe₂O₄/SnO₂ composite.

Photocatalytic degradation using RSM

The photocatalytic degradation experiment was designed using RSM based on CCD to investigate the influence of independent factors on the degradation efficiency of Congo red dye. RSM is based on a nonlinear multivariate model that employs an experimental design yielding enough response data to derive the most suitable mathematical model for the experiment [29]. The independent variables are solution pH (A), Congo red dye concentration (B), and irradiation time (B). Table 2 presents the degradation efficiency of the experimental data and forecasts for Congo red dye under visible light irradiation.

Table 2 Congo red dye degradation efficiency (%) based on experiments and predicted.

The results of ANOVA analysis of 20 experiments are presented in Table 3 to assess the suitability of the model. A p-value of < 0.05 signifies that the established quadratic model is statistically significant and suitable for predicting the efficacy of Congo red dye degradation. The 3 independent variables, pH (A), dye concentration (B), and irradiation time (C), exhibit p-values < 0.05, signifying their influence on degradation efficiency. The interactions between variables that do not affect one another are BC and C². The Lack of Fit score is not significant (p-value > 0.05), indicating that the quadratic model adequately represents the connection between the variables [37].

Table 3 ANOVA analysis for degradation photocatalytic of Congo red dye.

The coefficient of determination is close to 1 (R² = 0.9851), signifying a strong correlation between observed and predicted values (Table 4). Adjusted R² pertains to model performance, whereas predicted R² evaluates the model’s prediction capability on novel data. A disparity of less than 0.2 between adjusted R² and predicted R² values signifies commendable performance [38]. Adeq precision is used to evaluate the signal-to-noise ratio in the model. A precision number of 4 is preferable, indicating sufficient predictive capability.

Table 4 Fit statistic model for photocatalytic degradation of Congo red dye.

The model’s validity can be assessed by the normal distribution of the residuals and the graphs comparing predicted and experimental values. If the points on the graph align along a straight line (approaching the diagonal), the residuals are deemed to be normally distributed. Substantial divergences from this line suggest that the model fails to forecast accurately for certain data. Figure 7 illustrates a random distribution of data around the diagonal line, suggesting that the employed model predicts the response with considerable accuracy.

Figure 7 (a) The graphical plot of predicted versus experimental and (b) the normal probability plot.

The following is an expression for a quadratic model that explains the relationship between variables:

Degradation (%) = (171.19532 – 18.0455A – 0.442865B - 0.492599C + 0.127759AB + 0.052407AC +

0.003324BC + 0.531825A² – 0.036092B² + 0.001951C²) (2)

Figure 8 shows the contour plot and 3D surface response. This diagram illustrates the correlation between 3 independent factors and the response variable [39]. The 3D surface response demonstrates the variation of the response variable in relation to the interplay of 2 independent variables. The degradation efficiency is calculated by identifying the independent variable value that yields the optimal result. The degradation efficiency increases with decreasing pH and concentration, as evidenced by the red hue. The ZnFe₂O₄/SnO₂ composite possesses a pHpzc of 6.70, indicating that it is positively charged at solution pH values below this threshold. Electrostatic attractive interactions arise due to the anionic nature of Congo red dye, namely the ionization of the negatively charged sulfate group [22]. At elevated pH, the ZnFe₂O₄/SnO₂ composite combination exhibits a negative surface charge, which repels the negatively charged Congo red dye molecules. Additional research indicates that the degradation efficiency of Congo red is maximized at acidic pH levels [3,40].

Figure 8 3D surface and contour plot degradation photocatalytic of Congo red dye.

The efficacy of the photocatalytic degradation process is enhanced when the dye is uniformly distributed throughout the composite. Elevated dye concentrations inhibit the composite’s ability to absorb irradiation [41]. The degradation efficiency is higher at low concentrations. Extended irradiation correlates with increased deterioration efficiency, as the semiconductor absorbs a greater amount of light energy. When a semiconductor is exposed to light with enough energy, electrons from the valence band (VB) move to the conduction band (CB), creating electron-hole pairs (e⁻/h⁺). Electrons (e⁻) in the conduction band and holes (h⁺) in the valence band are crucial for the generation of reactive species [42].

To ensure that the predictive model generated from the RSM analysis is in accordance with the actual conditions, confirmation is needed. Confirmation is done by conducting additional experiments at optimum conditions and then comparing the experimental results with the model predictions. The recommended conditions, with a desirability of 1, include a pH of 4, a Congo red dye concentration of 10 mg/L, and an irradiation time of 80 min (Table 5). The predicted results were 97.10 % while the observed value was 96.12 %. The very small difference of degradation efficiency and in the range of the Prediction Interval (PI) Low and PI High indicates that the RSM model has a fairly accurate prediction. The study found that the degradation efficiency was better than in several other studies on Congo red dyes. Specifically, it reached 91.67 % with Pani@rGO/CuO and 93.77 % with rGO/Ag@ZnO [43,44].

Table 5 Validation of optimum conditions for photocatalytic degradation of Congo red dye.

Scavenger study

The scavenger study is employed to investigate the active species and the mechanism of electron transfer. The investigation utilized EDTA, BQ, and IPA. These 3 chemicals were added prior to the photocatalytic degradation of Congo red dye utilizing the ZnFe₂O₄/SnO₂ composite. The degradation mechanism was determined through the scavenger, which resulted in a substantial reduction in degradation efficiency. Figure 9 demonstrates that the ZnFe₂O₄/SnO₂ composite broke down 96.12 % of dye when no scavenger was used. However, when IPA, EDTA, and BQ were added, the breakdown degradation dropped to 72.56, 41.3, and 32.45 %, respectively. The results show that the main agents breaking down Congo red dye are BQ, especially superoxide radicals (•O₂⁻), followed by hydroxyl radicals (•OH⁻) and holes (ℎ⁺). Many studies show that superoxide radicals play an important role in breaking down substances, such as the Methylene blue dye when using Cu-doped α-MnO₂ [45] and the dye Congo red dye with Gd₂O₃ on g-C₃N₄ [46].

Figure 9 Experiments on trapping reactive species for ZnFe₂O₄/SnO₂ composite.

Recyclability study

The reusability of ZnFe₂O₄/SnO₂ composites is very important in cost-effectiveness, particularly when these composites are applied in industrial or environmental processes. To reuse ZnFe₂O₄/SnO₂, after the composite is used for photocatalytic degradation, it is separated from the solution using centrifugation. The composite is washed using distilled water and ethanol, followed by drying using an oven at a temperature of 80 °C for 2 h. The composite is reused for photocatalytic degradation of Congo red dye. The same work is carried out for 5 cycles. The degradation efficiency of 5 cycles is 95.23, 94.43, 93.51, 91.89, and 90.27 %. The decrease in degradation efficiency for each additional cycle shows that it is getting bigger, with an average decrease for each cycle of 1.2575 % (Figure 10). The loss of catalyst weight in subsequent cycles due to washing and drying may cause this phenomenon [47]. However, the ZnFe₂O₄/SnO₂ composite shows good performance because during 5 cycles, there is a decrease in degradation efficiency of only 4.96 %. This performance is better than the CoO-ZnO nanocomposite catalyst, which has a degradation efficiency reduction of 12.35 % in 5 cycles and 2.47 % in each cycle for the photocatalytic degradation of Methyl red dye [37]. The ability of composites to be reused effectively is an advantage because it minimizes costs in waste processing.

Figure 10 The cycling degradation of ZnFe₂O₄/SnO₂ composite.

Conclusions

ZnFe₂O₄/SnO₂ composite has been produced successfully with a mass ratio of ZnFe₂O₄ to SnO₂ of 1:2. The composite has magnetic features, a crystallite size of 17.50 nm, a saturation magnetization of 12.80 emu/g, and a band gap of 2.46 eV, which allows it to absorb visible light. A statistical study employing RSM with CCD yields a quadratic mathematical equation (p-value < 0.05, R² = 0.9851) that effectively characterizes the interaction among 3 independent variables. The best photocatalytic degradation was achieved at a pH of 4, a concentration of Congo red dye of 10 mg/L, and an irradiation time of 80 min. The reactive species involved in photocatalytic degradation are superoxide anion radicals (•O₂⁻). The catalyst has excellent stability, and the composite can be regenerated, with a degrading efficiency reduction of less than 5 % after up to 5 cycles. Consequently, the ZnFe₂O₄/SnO₂ composite holds significant potential for large-scale wastewater treatment applications.

Acknowledgements

The authors are grateful to the Directorate General of Higher Education, Research and Technology for the Tesis Magister scheme for the 2024 fiscal year, which is governed by contract number 090/E5/PG.02.00.PL/2024.

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