Enhanced Degradation of Methylene Blue and Methyl Orange Dyes Using Fe₃O₄@N-MWCNT as a Peroxymonosulfate Activator

Maksut Samedinov ^1,2 , Gulsin Arslan ¹ , Idris Sargin ^1,* 

1. Department of Biochemistry, Faculty of Science, Selçuk University, 42075, Konya, Turkey

2. Department of Chemistry, Faculty of Science, Selçuk University, 42075, Konya, Turkey

* Correspondence: Idris Sargin 

Academic Editor: Narendra Kumar

Received: January 12, 2026 | Accepted: July 28, 2026 | Published: August 04, 2026

Catalysis Research 2026, Volume 6, Issue 3, doi:10.21926/cr.2603009

Recommended citation: Samedinov M, Arslan G, Sargin I. Enhanced Degradation of Methylene Blue and Methyl Orange Dyes Using Fe₃O₄@N-MWCNT as a Peroxymonosulfate Activator. Catalysis Research 2026; 6(3): 009; doi:10.21926/cr.2603009.

© 2026 by the authors. This is an open access article distributed under the conditions of the Creative Commons by Attribution License, which permits unrestricted use, distribution, and reproduction in any medium or format, provided the original work is correctly cited.

1. Introduction

Textile wastewater poses a significant challenge because of the complexity and often hazardous nature of the discharges generated during textile manufacturing [1]. One of the primary pollutants in textile wastewater is organic dyes, which are widely used in textile manufacturing. These dyes have highly stable chemical structures, which slow and inefficiently degrade in the environment [2,3]. Because most dyes are water-soluble, they reduce light penetration in aquatic ecosystems, hindering photosynthesis and threatening aquatic biodiversity. This, in turn, increases oxygen demand, as reflected in elevated biochemical and chemical oxygen demand [4]. Even at low concentrations, they exert toxic, mutagenic, and carcinogenic effects and contribute to decreased dissolved oxygen levels [5]. Traditional water treatment methods for textiles often fall short because techniques such as membrane filtration, ozonation, adsorption, and coagulation don’t effectively degrade dyes. That’s why there’s a need for a new, eco-friendly approach to remove organic dyes from water.

Methylene Blue (MB) is a common dye found in textile wastewater. It’s a thiazine dye with the chemical formula C₁₆H₁₈ClN₃S and can also exist as a hydrate, C₁₆H₁₈ClN₃S·H₂O [6]. Recent research indicates that at high concentrations, MB can interfere with oxygen uptake by hemoglobin, potentially leading to hypoxia [7]. At excessive doses, this dye can also raise methemoglobin levels, which hampers oxygen transport in the body [8]. Additionally, MB acts as a monoamine oxidase inhibitor (MAOI), affecting serotonin levels. When combined with other serotonergic agents, it may trigger serotonin syndrome, characterized by symptoms such as fever, sweating, confusion, tremors, and seizures [9]. Given the toxic effects of MB, exploring effective methods for treating wastewater containing MB is an important area of investigation.

In addition to MB, other dyes, such as Methyl Orange (MO), can also affect human health. MO is a synthetic acid-base indicator with the chemical formula C₁₄H₁₄N₃NaO₃S, used for pH testing and as a coloring agent in chemical and biological labs [10]. In textile wastewater, it is often used for purposes similar to MB. Although their applications overlap, it is important to note that MO can be equally toxic as MB even at lower concentrations [11].

Recent research shows that advanced oxidation methods, which use various reactive oxygen species (ROS) in chemical remediation, are effective at degrading dyes in water. Among these methods, sulfate radical-based processes are particularly powerful for degrading persistent organic pollutants in complex aqueous environments [12]. Potassium peroxymonosulfate (KHSO₅) is a typical persulfate salt with an asymmetric structure and is widely used to generate reactive oxygen species, such as sulfate and hydroxyl radicals, for further oxidation. Transition metals such as Fe, Co, and Mn, and their oxides, are excellent activators of peroxymonosulfates; they facilitate the formation of radical species (SO₄^•-, ^•OH) [13,14].

Studies in the literature on PMS activation indicate that activation occurs through conversion to active oxidant species. Possible reactions after activation are listed below.

1. S₂O₈^2- → 2SO₄^•-
2. HSO₅^- → SO₄^•- + HO^•
3. SO₄^•- + H₂O → SO₄^2- + HO^• + H⁺

Literature reports that the high performance of Fe- and N-doped carbon-based catalysts in PMS activation stems from structural and electronic synergy. Nitrogen doping enhances the electron conductivity of the carbon and promotes the formation of graphitic N and Fe-N active sites, thereby facilitating PMS adsorption and activation. Meanwhile, iron species within the carbon matrix accelerate electron transfer and the Fe³⁺/Fe²⁺ redox cycle, supporting both radical and non-radical mechanisms. This synergistic effect significantly enhances catalytic activity and PMS activation efficiency [15,16,17].

When exposed to oxidizing agents or other aggressive species in aqueous solutions, MO can initiate radical attacks on azo compounds, leading to toxic effects. The literature confirms that breaking the azo bond in the MO molecule can release aniline derivatives, which are known for their toxicity and carcinogenicity [18].

Advanced oxidation processes (AOPs) that combine peroxymonosulfate (PMS) with various catalysts or under different conditions have attracted significant attention for their efficacy in degrading persistent organic pollutants. For instance, when PMS is used with activated carbon fibers, it greatly enhances the breakdown of these pollutants, resulting in high removal efficiencies [19]. This highlights the potential of combining diverse materials and methodologies to enhance PMS activation for environmental applications.

This study involves the preparation of a heterogeneous catalyst (Fe₃O₄@N-MWCNT). This catalyst activates peroxymonosulfate to degrade MB and MO dyes in an aqueous solution. MB and MO dyes were chosen as model compounds to evaluate the effectiveness of the synthesized catalyst in dye degradation. The novelty of this work lies in the design and synthesis of a magnetically recoverable Fe₃O₄@N-MWCNT nanocomposite, where the synergistic interaction between Fe₃O₄ nanoparticles and N-MWCNTs enhances catalytic performance.

2. Experimental

2.1 Materials

Iron(III) chloride hexahydrate (FeCl₃·6H₂O), iron(II) chloride tetrahydrate (FeCl₂·4H₂O), hydrochloric acid (HCl), nitric acid (HNO₃), ethanol (C₂H₅OH), urea (NH₂CONH₂), methylene blue (C₁₆H₁₈ClN₃S), and methyl orange (C₁₄H₁₄N₃NaO₃S) were obtained from Merck. Potassium peroxymonosulfate (PMS) and ammonia solution (NH₃·H₂O) were obtained from Sigma-Aldrich. Aldrich supplied multi-walled carbon nanotubes (MWCNT).

2.2 Synthesis of the Catalysts

Three types of carbon-based catalysts, known as carbocatalysts, were produced: N-MWCNT, Fe₃O₄@MWCNT, and Fe₃O₄@N-MWCNT (Figure 1). In brief, MWCNTs were processed in a highly acidic environment to create functionalized MWCNTs, specifically in a carboxylated/hydroxylated form. Following this, the functionalized MWCNT was treated with an alkaline solution of Fe²⁺/Fe³⁺ to yield Fe₃O₄@MWCNT, or it was reacted with urea to produce N-doped MWCNT (N-MWCNT). Subsequently, N-MWCNT underwent treatment in an alkaline solution of Fe²⁺/Fe³⁺ to generate Fe₃O₄@N-MWCNT. Further details are provided below.

Figure 1 The steps for the synthesis of the catalysts.

2.2.1 Preparation of Functionalized MWCNTs

1.0 g of MWCNTs was treated in a strongly acidic medium (1:3 molar ratio of hydrochloric acid and nitric acid) at 60°C for 12 h under magnetic stirring. After treatment, MWCNTs were washed several times with ethanol and distilled water and dried in an oven at 80°C for 4 h. This process led to the formation of carboxyl and hydroxyl groups on the surface of carbon nanotubes. After the drying was complete, it was observed that MWCNTs exhibited hygroscopic properties, so the drying was performed in a lyophilizer. The carboxyl groups formed facilitated the binding of magnetite (Fe₃O₄) particles and N-doping of the carbon nanotubes with urea (vide infra).

2.2.2 Synthesis of N-MWCNT

0.5 g of carboxylated MWCNT was thoroughly mixed with 1.5 g of urea. To this mixture, 50 mL of ultrapure water was added, and the solution was sonicated for 4 h to achieve a uniform structure. After sonication, the mixture was washed with ethanol to remove impurities, and the remaining liquid was lyophilized. This process enabled chemical modifications of the MWCNT surface, resulting in N-doping.

2.2.3 Synthesis of Fe₃O₄@MWCNT

1.0 g of carboxylated MWCNT was added to 100 mL of pure water to form a dispersion. Next, 0.225 g of FeCl₂·4H₂O was added, and the mixture was stirred at 70°C for 1 h. At the end of this period, 0.375 g of FeCl₃·6H₂O was added, and stirring continued for another 1 h at the same temperature. Then, 4.0 mL of NH₃ solution was added, and the reaction medium was stirred for 1 h. Finally, MWCNT loaded with magnetic particles (Fe₃O₄@MWCNT) was filtered and washed with water. The Fe₃O₄@MWCNT was dried in an oven at 80°C for 5 h and subsequently lyophilized. After drying, the magnetic properties were assessed.

2.2.4 Synthesis of Fe₃O₄@N-MWCNT

A dispersion was formed by adding 0.5 g of N-MWCNT to 50 mL of pure water. Then, 0.113 g of FeCl₂·4H₂O was introduced into this dispersion, and the mixture was stirred at 70°C for 1 h. After stirring, 0.186 g of FeCl₃·6H₂O was added, and the mixture was stirred for another hour at the same temperature. Next, 2.0 mL of NH₃ solution was added to the mixture, and the mixture was stirred for an additional hour. Following this, N-MWCNTs loaded with magnetic particles (Fe₃O₄@N-MWCNT) were filtered, washed with water, and dried in an oven at 80°C for 5 h. After drying, the samples were lyophilized. The magnetic properties of the resulting magnetic N-MWCNTs were then evaluated.

2.3 Instrumentation and Characterization

The FT-IR spectra of Fe₃O₄@N-MWCNT were recorded using a Bruker Vertex 70 FTIR spectrometer within the range of 4000–500 cm^-1 to identify the functional groups on the catalyst surface. This analysis was performed to confirm the presence of imine and amino groups after N-doping. Additionally, the interaction between MWCNT and Fe₃O₄ nanoparticles was examined through characteristic spectral peaks. The crystalline phases of Fe₃O₄@N-MWCNT were investigated using X-ray diffraction (XRD). The analysis provided insights into the crystallinity and graphitic nature of MWCNT and the distinct crystalline structures of Fe₃O₄ (magnetite) nanoparticles. Transmission Electron Microscopy (TEM) was used to examine the catalyst’s nanoscale morphology, size, and distribution. The images revealed uniform attachment of Fe₃O₄ nanoparticles to the MWCNT surface, highlighting the homogeneity of the composite. Differential Scanning Calorimetry (DSC) was performed to evaluate the thermal stability of Fe₃O₄@N-MWCNT. This technique provided information on the thermal resistance and chemical stability of the catalyst under varying temperature conditions, enabling the determination of optimal operating conditions.

2.4 Degradation of MB and MO Dyes

MB and MO stock solutions were prepared by dissolving certain amounts of the dyes in distilled water to give a final concentration of 1.0 × 10^-4 M. In the degradation studies, MB and MO solutions were mixed with the Fe₃O₄@N-MWCNT catalyst, and degradation was initiated by the addition of PMS. Once the characteristic color of the dyes disappeared, the clear solution was immediately pipetted into a quartz cuvette and monitored using a UV-vis spectrophotometer at the specific absorbance for each degradation experiment. In the case of MB, the degradation was evidenced by the disappearance of the peak at 664 nm, whereas for MO, it was shown by the absence of the peak at 464 nm. Additionally, methanol (15% v/v) was added as a radical scavenger to effectively quench sulfate and hydroxyl radicals, although it did not fully deactivate PMS.

In the study, a heterogeneous Fe₃O₄@N-MWCNT catalyst was used, which was quickly separated by magnetic filtration before quenching to prevent further PMS activation and oxidation. Reaction conditions and reusability tests for the Fe₃O₄@N-MWCNT catalyst are detailed in Table 1, Table 2, and Table 3. The temperature of the reaction vessel was maintained with a water bath during temperature studies.

Table 1 The catalytic activity of the functionalized MWCNT, N-MWCNT, Fe₃O₄@MWCNT, and Fe₃O₄@N-MWCNT in the degradation of MB dye (pH 8.0).

Table 2 The catalytic activity of the functionalized MWCNT, N-MWCNT, Fe₃O₄@MWCNT, and Fe₃O₄@N-MWCNT in the degradation of MO dye (pH 7.4).

Table 3 The reaction times that were recorded after the Fe₃O₄@N-MWCNT catalyst was reused in the degradation of the MB and MO (1.0 mL dye solution, 3 mg Fe₃O₄@N-MWCNT, C_PMS: 8.45 mM (MB) and 4.23 mM (MO), 21°C).

2.4.1 Reusability Tests

In reusability tests, the Fe₃O₄@N-MWCNT catalyst was recovered using a magnet, washed with distilled water, dried, and reused in the degradation of MB or MO to demonstrate the catalyst’s stability and reusability over multiple cycles (5 cycles).

2.4.2 Degradation of MB and MO Dyes Without PMS Activator

The degradation of MB and MO dyes without a PMS activator (i.e., Fe₃O₄@N-MWCNT) was studied under optimal conditions (i.e., the entries that yielded the shortest degradation times in Table 1 and Table 2). The degradation process was monitored spectrophotometrically.

3. Results and Discussion

3.1 Characterization of Fe₃O₄@N-MWCNT Catalyst

3.1.1 TEM Analysis

TEM analysis was conducted to examine the size and morphology of the Fe₃O₄@N-MWCNT catalyst. TEM analysis showed that the Fe₃O₄ nanoparticles were mostly spherical, but their distribution in the N-MWCNT matrix was uneven. Some aggregation of the nanoparticles was observed, likely due to magnetic interactions between the Fe₃O₄ particles and variations in surface defects and topography of the MWCNT. This uneven distribution could affect the catalytic properties of the composite, resulting in localized areas with higher activity (Figure 2).

Figure 2 TEM images of Fe₃O₄@N-MWCNT (scale bars: A: 200 nm, B: 100 nm, C: 50 nm, and D: 20 nm).

The fibrous network in TEM images (Figures 2A, 2B) is attributed to N-MWCNT, which serves as a conductive and structurally supportive framework [20]. The dark, agglomerated regions dispersed along the nanotubes correspond to Fe₃O₄ nanoparticles affixed to the N-MWCNT surface via electrostatic interactions and functionalization. Higher magnification TEM images (Figures 2C, 2D) further reveal the morphology of the Fe₃O₄ nanoparticles, showing their tendency to cluster while maintaining a nanoscale dispersion [21]. The nanoparticle size remains consistent at roughly 20 nm in diameter, indicating controlled synthesis and uniform dispersion [22].

3.2 FT-IR Spectroscopy Analysis of Fe₃O₄@N-MWCNT

Figure 3, Figure 4, and Figure 5 present the FT-IR spectra of the catalysts, which were analyzed to identify the organic functional groups present in the catalysts. FT-IR spectroscopy was used to identify the functional groups responsible for the catalytic degradation of dyes. The results highlight chemical interactions and confirm the successful formation of the catalyst, which played a key role in dye-degradation processes as follows [23,24,25]: The FT-IR spectra comparison between pristine MWCNT and acidified MWCNT shows notable differences due to surface modification. The peak around 1660 cm^-1 in the carboxylated MWCNT spectrum corresponds to the C=O stretch of carboxyl groups, indicating successful functionalization. Additionally, the broad band between 2750–3500 cm^-1 is attributed to O–H stretching from the carboxyl groups and adsorbed water. The bands at 1103, 1005, 869, and 542 cm^-1 in the fingerprint region reflect the nanotube structure and modifications from oxygenated groups. Conversely, weaker, less-defined bands in these regions for pure MWCNT suggest fewer oxygen functional groups. Overall, FT-IR results confirm effective carboxylation and surface functionalization of MWCNT with oxygen-containing groups.

Figure 3 FT-IR spectra of carboxylated MWCNT (MWCNT-COOH) and pristine MWCNT.

Figure 4 FT-IR spectra of carboxylated MWCNT (MWCNT-COOH), nitrogen-doped MWCNT (N-MWCNT), and magnetite-loaded MWCNT (Fe₃O₄-MWCNT).

Figure 5 FT-IR spectra of magnetite-loaded N-MWCNT (Fe₃O₄@N-MWCNT) and nitrogen-doped MWCNT (N-MWCNT).

Analyzing the FT-IR spectra of MWCNT-COOH, N-MWCNT, and Fe₃O₄-MWCNT samples highlights the emergence of distinct vibrational bands at each stage of modification. The broad absorption around 3400 cm^-1 in N-MWCNT spectra corresponds to N–H stretching vibrations. Additionally, bands between 1558–1527 cm^-1 indicate successful nitrogen incorporation and the formation of nitrogenous groups. For Fe₃O₄-MWCNT, notable bands in the 500–600 cm^-1 range are observed, particularly around 544 cm^-1 and 422 cm^-1, which are associated with Fe₃O₄ stretching vibrations and confirm the attachment of Fe₃O₄ nanoparticles. These bands serve as characteristic FT-IR signatures of spinel-structured iron oxides. Overall, the spectral data confirm the successful nitrogen doping and Fe₃O₄ loading processes at each modification step.

Comparing the FT-IR spectra of N-MWCNT and Fe₃O₄@N-MWCNT samples reveals characteristic spectral changes due to the successful loading of Fe₃O₄ nanoparticles onto the nitrogen-doped carbon nanotube surface. In the spectrum of the Fe₃O₄@N-MWCNT composite, new and broad absorption bands, particularly in the 500–600 cm^-1 range, are noteworthy. These bands correspond to Fe–O stretching vibrations and confirm the successful immobilization of Fe₃O₄ nanoparticles onto the carbon nanotube surface. Furthermore, the decrease in intensity or broadening of some sharp bands observed in the N-MWCNT spectrum and their absence in the Fe₃O₄@N-MWCNT spectrum indicate the formation of strong interactions between Fe₃O₄ nanoparticles and the nitrogen-doped carbon nanotube surface, suggesting a change in the chemical environment of the surface. These findings provide significant characterization evidence demonstrating the successful structural achievement of the synthesized Fe₃O₄@N-MWCNT composite.

3.3 XRD Analysis of Fe₃O₄@N-MWCNT

The XRD pattern shows distinct peaks at 2θ values of around 26° and 44° (Figure 6). These peaks correspond to the (002) and (100) planes of N-MWCNT, respectively, confirming the presence of carbon nanotubes. Additionally, other peaks at approximately 18°, 30°, 35.5°, 53°, 57°, 62.5°, and 74.5° in 2θ indicate Bragg reflections from the (111), (220), (311), (422), (511), (440), and (533) planes of Fe₃O₄ [26]. These characteristic peaks confirm the presence of the spinel crystal structure of Fe₃O₄, indicating the successful synthesis of the nanocomposite. The XRD analysis also demonstrates that the nanocomposite possesses a well-defined and highly ordered crystalline structure, confirming its crystalline nature rather than an amorphous phase [27].

Figure 6 XRD pattern of Fe₃O₄@N-MWCNT.

3.4 DSC Analysis of Fe₃O₄@N-MWCNT

In the DSC analysis (Figure 7), a distinct endothermic event was observed, starting at 137.96°C, peaking at 161.39°C, and ending at 178.29°C. This sharp endothermic peak indicates the material’s melting and a significant structural change. The enthalpy change, calculated from the peak area, was -13.83 mJ, corresponding to a normalized value of -7.68 J/g, indicating a substantial amount of energy required for the phase transition. These results strongly suggest a well-defined thermal response, confirming the material’s structural stability and phase behavior under thermal stress [28].

Figure 7 DSC analysis of Fe₃O₄@N-MWCNT.

3.5 Catalytic Activity of Fe₃O₄@N-MWCNT in the Degradation of Dyes

Conventional oxidation and adsorption techniques often have limited efficiency, high operating costs, and cause secondary pollution. Therefore, creating multifunctional nanocomposites that can efficiently activate peroxymonosulfate (PMS) to generate reactive oxygen species under mild conditions has become a key research area.

The catalytic activity of the functionalized MWCNT, N-MWCNT, Fe₃O₄@MWCNT, and Fe₃O₄@N-MWCNT in the degradation of MO and MB dyes is shown in Table 1 and Table 2. The results presented in Table 1 and Table 2 demonstrate that Fe₃O₄@N-MWCNT is a superior peroxymonosulfate activator for the degradation of MB and MO dyes in aqueous media. This observation also demonstrates the effects of N doping. Compared to Fe₃O₄@N-MWCNT, Fe₃O₄@MWCNT was significantly less effective as a peroxymonosulfate activator in degrading MB and MO dyes. As presented in Table 3, Fe₃O₄@N-MWCNT maintained its activity over 5 cycles, demonstrating its reusability in environmental applications and remediation. Additionally, the catalyst was easily recovered from the medium with a magnet, another advantage.

In chemical remediation technology, advanced oxidation processes (AOPs) have recently been reported to effectively degrade plastic pollutants in water through various reactive oxygen species (ROS) [29]. Among these processes, sulfate radical (SO₄^•-)–based methods stand out as highly effective for degrading recalcitrant organic pollutants in complex water matrices [12]. Peroxymonosulfate (HO-SO₄^-), an asymmetric persulfate salt, is commonly used in advanced oxidation processes to generate highly reactive oxygen species, such as SO₄^•- and HO^• radicals [30]. Transition metals (e.g., Fe, Co, Mn) and their oxides serve as excellent catalysts for activating peroxymonosulfate, promoting the formation of SO₄^•- and HO^• species [13]. Doping heteroatoms such as B, N, S, and P into the sp² carbon lattice of carbon nanotubes can enhance the catalytic efficiency of the active sites for peroxymonosulfate activation [31]. Consequently, heteroatom-doped carbon nanotubes and transition-metal-based catalysts are promising materials for the effective breakdown of environmental pollutants.

Magnetite nanoparticles have excellent magnetic and electrical properties that facilitate electron transfer between ferrous and ferric ions. They activate O–O bonds in persulfate, hydrogen peroxide, and PMS, generating reactive oxygen species [32]. Oxidant molecules adsorb onto magnetite particles, and ferrous ions in nanoparticles donate electrons, generating radicals such as superoxide, hydroperoxyl, and sulfate radicals [33].

As presented in Table 1 and Table 2, with a constant catalyst dosage, the catalytic performance of the synthesized Fe₃O₄@N-MWCNT composite was systematically evaluated for MB degradation via PMS activation. Comparative studies confirmed that the synergistic interaction between the nitrogen-doped carbon framework and the encapsulated iron species enabled ultra-fast degradation. Optimization of operational parameters further demonstrated that increasing catalyst loading to 3 mg accelerated radical generation, reducing reaction time to 32 s by maximizing active site density. Moreover, the system exhibited remarkable robustness across varying pollutant loads. It achieved complete degradation within 21 s at 40°C, underscoring its high thermal sensitivity and potential for efficient, large-scale water treatment applications. The catalytic performance of the Fe₃O₄@N-MWCNT composite was further confirmed using MO as a model pollutant. The composite exhibited superior activity compared with pristine and control samples, achieving complete MO degradation within 63 s. Optimization studies revealed that increasing catalyst dosage significantly enhanced reaction kinetics, reducing the degradation time to 6 s at 3 mg catalyst loading. Moreover, the system maintained excellent performance across varying pollutant loads and elevated temperatures, demonstrating the potential of Fe₃O₄@N-MWCNT as an efficient PMS activator for advanced oxidative water treatment.

The reusability tests revealed that the catalytic activity of Fe₃O₄@N-MWCNT started to decline, especially after the third cycle (Table 3). This decrease may be due to the catalyst loss during recovery. However, the catalyst still performed well even after the fifth cycle.

3.6 Degradation of MB and MO Dyes without PMS Activator

The degradation of MB and MO dyes was investigated in the absence of a PMS activator (i.e., Fe₃O₄@N-MWCNT) under optimal conditions (please refer to the best degradation times in Table 1 and Table 2). The process was monitored using UV-vis spectrophotometry (Figure 8). The degradation of MO dye took 20 min, whereas the degradation of MB dye required up to 180 min. These findings indicate that a PMS activator, such as Fe₃O₄@N-MWCNT, is necessary to achieve effective results when using PMS as a radical source. Previous studies confirm that while PMS is a thermodynamic oxidant, its direct reaction with most contaminants is impractical. Thus, a catalyst activation is necessary [34,35]. Table 4 summarizes recent studies on the activation of peroxymonosulfate for pollutant degradation.

Figure 8 The degradation of MO and MB dyes in the absence of the PMS activator (i.e., Fe₃O₄@N-MWCNT) under optimal conditions.

Table 4 Comparison of recently published studies on peroxymonosulfate activation for pollutant degradation.

4. Conclusion

This study revealed that (i) peroxymonosulfate decomposition, which generates radical species such as SO4^•- and HO^•, has significant potential for treating water contaminated with Methylene Blue and Methyl Orange dyes. (ii) Peroxymonosulfate decomposition requires activation by a catalyst containing a transition metal. (iii) Magnetite (Fe₃O₄), a double oxide, is an effective activator of peroxymonosulfate. (iv) N-doping of MWCNT is necessary to enhance the catalytic performance of the Fe₃O₄@N-MWCNT catalyst system. (v) Fe₃O₄@N-MWCNT can maintain its activity over five cycles. The study also found that N-doping of MWCNT influences the catalytic activity of the Fe₃O₄@N-MWCNT system during peroxymonosulfate decomposition. Fe₃O₄@N-MWCNT appears promising for water treatment, especially for removing Methylene Blue and Methyl Orange from aqueous media. It acts as an efficient, magnetically recoverable peroxymonosulfate activator, achieving dye degradation in seconds and retaining activity over five reuse cycles. However, the Fe₃O₄@N-MWCNT catalyst system should be tested in a pilot system. This should be explored further in future studies.

Author Contributions

Maksut Samedinov: Conceptualization, Formal analysis, Investigation, Methodology, Visualization, Writing – original draft. Idris Sargin: Supervision, Writing – original draft, Writing – review & editing. Gulsin Arslan: Conceptualization, Supervision, Writing – review & editing.

Funding

This study was partially funded by TUBITAK 2209-A program (Grant no: 1919B012301017).

Competing Interests

The authors have declared that no competing interests exist.

AI-Assisted Technologies Statement

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