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Article

Efficient and Thorough Oxidation of Bisphenol A via Non-Radical Pathways Activated by SOx2−-Modified Mn2O3

by
Fei Pei
1,2,*,
Jiajie Dong
3,
Xin’e Yan
1,2,*,
Youwen Xu
1 and
Songyuan Yao
1
1
School of Civil Engineering, Xian Traffic Engineering Institute, Xi’an 712000, China
2
Xi’an Key Laboratory for Monitoring and Prevention of Railway Track Subgrade and Bed Diseases, Xi’an 710065, China
3
Qinchuan Machine Tool & Tool Group Co., Ltd., Xi’an R&D Branch, Xi’an 710301, China
*
Authors to whom correspondence should be addressed.
Crystals 2025, 15(11), 922; https://doi.org/10.3390/cryst15110922
Submission received: 9 September 2025 / Revised: 20 October 2025 / Accepted: 22 October 2025 / Published: 27 October 2025
(This article belongs to the Section Inorganic Crystalline Materials)
Browse Figures
Versions Notes

Abstract

It is generally found that enhancement in catalytic activity comes at the expense of selectivity or stability. In this study, an SOx2−-modified Mn2O3 (SO-Mn2O3) solid catalyst was prepared using a simple oxalate precipitation method. This catalyst exhibited not only high catalytic activity but also high selectivity and good cycling stability. The degradation ratio of bisphenol A (BPA) under SO-Mn2O3 activated potassium peroxymonosulfate (PMS) achieved over 99% within 10 min, and the mineralization ratio increased to 83.2%. Particularly, the degradation rate for BPA under the SO-Mn2O3/PMS system was 15 times that of Mn2O3. Furthermore, the degradation ratio remained at 93.3% after five consecutive cycles. Multiple experimental characterizations confirmed that the introduction of SOx2− into Mn2O3 shifted the oxidative degradation pathway from a mixture of radical and non-radical routes to a predominantly non-radical pathway. This suppressed radical generation promoted the selective formation of high-valence metallic-oxo (Mn(V)=O) species and singlet oxygen (1O2), thereby significantly enhancing the catalytic activity. In addition, the SO-Mn2O3/PMS system exhibited broad applicability towards the degradation of other phenolic pollutants, strong anti-interference capability against complex water matrices, and suitability for efficient removal of organic contaminants in such environments. This research offers new perspectives for the design of selective catalysts for PMS activation.

1. Introduction

The deep treatment of persistent organic pollutants (POPs) in aquatic environments represents a pressing global challenge because it poses severe threats to human health and ecological security. Phenolic pollutants, particularly BPA, which is widely used in manufacturing, are being extensively released into the environment through industrial wastewater, posing a serious threat to ecosystems and human health [1,2]. As a typical endocrine-disrupting chemical, BPA is frequently detected in natural water bodies and wastewater at concentrations ranging from 1 μg L−1 to 17 mg L−1. Its acute toxicity to aquatic organisms and adverse effects on male reproductive and thyroid functions in humans have been confirmed, highlighting the urgency of its complete removal from source wastewater. However, existing wastewater treatment technologies face significant challenges. Conventional biological degradation and physical adsorption processes exhibit limited removal efficiency for BPA, allowing it to enter the aquatic environment as a persistent organic pollutant. Consequently, developing highly efficient and reliable advanced treatment technologies to eliminate persistent organic pollutants like BPA is an urgent global task for safeguarding ecological security and public health.
PMS-based advanced oxidation processes (PMS-AOPs) have emerged as a promising technology for water treatment and are widely employed for organic pollutant removal [3,4,5]. However, highly reactive sulfate radical (SO4•−) and hydroxyl radical (•OH) suffer from significant matrix interference (e.g., inorganic anions, humic acid) during practical water treatment applications, leading to drastically reduced treatment efficiency in real water systems [6,7,8]. Consequently, non-radical oxidation pathways—characterized by strong matrix interference resistance and high selectivity—are better suited for organic pollutant degradation in complex aqueous matrices. Developing novel solid catalysts to activate PMS for the efficient and selective generation of non-radical oxidizing species is critically important for wastewater remediation. Mn(V)=O species and singlet oxygen (1O2) represent highly effective non-radical reactive species with significant promise for organic wastewater treatment. These species exhibit extended lifetimes, high oxidant utilization efficiency, and strong resistance to interference from non-target substrates, particularly demonstrating high selectivity toward recalcitrant organic pollutants bearing electron-donating groups [9,10,11,12]. Metallic elements, such as Co and Fe, have been extensively applied in developing catalysts for PMS activation, while they predominantly trigger Fenton-like reactions via radical pathways [13,14,15]. Manganese (Mn) offers abundant natural reserves, environmental compatibility, and redox versatility. Particularly, manganese oxides (MnOx) exhibit exceptional sensitivity in modulating PMS activation modes toward non-radical species (Mn(V)=O and 1O2) in contrast to Co and Fe [16,17,18,19,20]. Among them, the non-radical Mn(V)=O species refer to complexes or ions formed by the specific chemical bonding between Mn and the oxygen atom from reactions between low-valent Mn ions and PMS, similar to these kinds of species reported previously [21,22]. Recent studies confirmed that surface-modified MnOx via defect engineering or heteroatom doping facilitated 1O2 generation from PMS [23,24,25,26]. However, the incorporation of guest metal atoms induces undesirable side reactions. For instance, the insertion of Fe into manganese oxides (MnFeO) promoted 1O2 production but simultaneously resulted in the formation of radical species (SO4•− and •OH) during PMS activation [27]. Similar phenomena were found in other metal-modified MnOx systems [25].
Sulfur modification can modulate redox processes by altering the surface microenvironment of metal oxides (e.g., surface electronic structure, lattice strain, and molecular dynamics) [28,29,30,31]. Typically, changes in the surface microenvironment of metal oxides induce modifications in electronic structure and crystal lattice, thereby influencing the adsorption behavior of guest molecules and ultimately determining the catalytic reaction pathways on the surface [32,33,34]. Notably, PMS activation pathways and their molecular adsorption configuration are intrinsically linked to metal centers, particularly oxygen sites of PMS [35,36]. Thus, tailoring the structure and chemical properties of manganese oxides through sulfur modification represents an attractive strategy for regulating non-radical oxidation pathways in PMS-AOPs systems.
Herein, an SOx2−-modified manganese sesquioxide (SO-Mn2O3) solid catalyst was constructed for PMS activation to selectively generate non-radical oxidizing active species (Mn(V)=O species and 1O2), achieving efficient degradation and deep oxidation of phenolic organic pollutants. The removal ratio of BPA increased by 15 times under the catalysis of SO-Mn2O3 in comparison to that catalyzed by Mn2O3, achieving a mineralization ratio exceeding 80% within 10 min. The SO-Mn2O3 catalyst also demonstrated superior anti-interference capability and reusability, being bound to become a promising catalyst in wastewater treatment in practical applications.

2. Materials and Methods

2.1. Reagents

Sodium thiosulfate (Na2S2O3), BPA (C15H16O2), manganese(II) acetate tetrahydrate (Mn(CH3COO)2·4H2O), phenol (C6H6O), 4-chlorophenol (4-CP), 2,3-dichlorophenol (2,3-DCP), PMS (KHSO5), oxalic acid (H2C2O4), tert-butanol (TBA), potassium thiocyanate (KSCN), methanol (CH3OH), sodium azide (NaN3), potassium iodide (KI), terephthalic acid (TPA), methyl phenyl sulfoxide (PMSO), p-hydroxybenzoic acid (HBA), benzoquinone (BQ), and 9,10-anthracenediyl-bis(methylene) dimalonic acid (ABDA) were all analytical grade and purchased from China National Medicines Chemical Reagents Co., Ltd.( Shanghai, China).

2.2. Synthesis and Characterization of SO-Mn2O3

A homogeneous solution (solution A) was prepared by dissolving 2.3 g of Mn(CH3COO)2·4H2O and 4.92 g of Na2S2O3 in 50 mL of ultrapure water. Solution B was obtained by dissolving 5.2 g of H2C2O4 in 50 mL of ultrapure water. Then solution B was maintained at 60 °C under magnetic stirring. Solution A was added dropwise into solution B, and the reaction proceeded for 30 min. The resulting suspension was filtered, thoroughly washed, and dried in sequence. Subsequently, the solid products were calcined at 500 °C for 2 h, and SO-Mn2O3 was obtained. For comparison, pristine Mn2O3 was synthesized following an identical procedure without Na2S2O3 addition. The samples were systematically characterized using the following instruments (Table 1).

2.3. Catalytic Degradation and Quenching Experiments

The phenolic solutions were prepared by dissolving 2 mg of BPA, phenol, 4-CP, or 2,3-CP into 100 mL of deionized water under stirring, respectively. Catalytic degradation experiments were conducted in 150 mL glass reactors containing 100 mL of phenolic solutions under dark conditions at 25 °C. An amount of 20 mg of the SO-Mn2O3 and Mn2O3 catalysts was dispersed in solutions of the above target phenolics under magnetic stirring, respectively. After reaching adsorption equilibrium, PMS was introduced to initiate catalytic degradation. During the degradation process, 3.0 mL of the above solution was collected at 2-minute intervals using a syringe, immediately filtered through a PTFE-membrane filter, and then quenched with 0.01 mL of 0.1 M Na2SO3. The quenched solutions were analyzed by HPLC to determine the degradation ratio of phenolics. Quenching experiments followed identical procedures except that PMS and radical scavengers were added simultaneously into the catalytic systems.

2.3.1. Active Oxidizing Species Detection

The concentration of organic compounds was analyzed using an Agilent 1100 HPLC equipped with a Hypersil ODS column. The mobile phase and detection wavelength were set as follows: acetonitrile and water (v/v: 20/80), detection wavelength λ = 254 nm. Degradation kinetics were fitted using the pseudo-first-order model, and the reaction rate constant was calculated according to Equation (1):
ln (Ct/C0) = −kt
where Ct is the concentration of the target pollutant at a given reaction time (t), and C0 is the initial concentration of the target pollutant.

2.3.2. Detection of •OH Radicals

Fluorometric method: 20 mg of catalyst was dispersed in 50 mL of an aqueous terephthalic acid solution (0.2 mmol/L). The mixture was sonicated for a period of time (generating 2-hydroxyterephthalic acid, with an absorption peak at 425 nm). The solution was filtered (sampled every 2 min for testing), and its fluorescence spectrum (PL) was measured using a fluorescence spectrophotometer. The amount of •OH was indirectly measured using PL emission spectroscopy (excitation wavelength: 412 nm).

2.3.3. Detection of Singlet Oxygen (1O2)

Ultraviolet-visible spectrophotometry: 20 mg of catalyst was dispersed in 50 mL of a solution of ABDA (5 × 10−5 mol/L) with DMSO and water as solvents (v/v: 1/100). The mixture was sonicated for a period of time. The solution was filtered and measured using an ultraviolet-visible spectrophotometer, with a test wavelength range of 200~800 nm. Its absorption peak is located between 350 and 410 nm.

2.3.4. Detection of SO4•− Radicals

The concentration variation in BQ was detected to indirectly reflect the concentration variation in SO4•−, the main degradation byproduct of HBA. 20 mg of catalyst was dispersed in 50 mL of an aqueous HBA solution, followed by the addition of 10 mg PMS. The mixture was stirred and reacted for a period of time (PMS: HBA, molar ratio: 1/2). Catalyst particles were removed by filtration using a PTFE syringe filter disk (0.22 μm). The sample was immediately quenched with 0.1 mM Na2S2O3 solution, and then the BQ content in the sample was determined by ultraviolet-visible spectrophotometry.

2.3.5. Detection of High-Valent Metal Ions

An amount of 20 mg of catalyst was dispersed in 50 mL of an aqueous PMSO solution (20–500 µmol/L), followed by the addition of 10 mg of PMS. The mixture was stirred and reacted for a period of time. The solution was filtered, and the PMSO2 produced in the sample was determined using HPLC. The mobile phase and detection wavelength were set as follows: acetonitrile and water (v/v: 20/80), detection wavelength λ = 254 nm.

3. Results

3.1. Structure and Chemical Composition of Mn2O3 and SO-Mn2O3

Transmission electron microscopy (TEM) images of Mn2O3 (Figure S1a) and SO-Mn2O3 (Figure 1a) demonstrated that both types of nanoparticles with irregular morphology and particle sizes of 20~40 nm were aggregated. The HRTEM image showed clear lattice fringes with the d-spacing of 0.27 nm in the Mn2O3 sample (Figure S1b) and 0.38 nm in the SO-Mn2O3 sample (Figure 1b), which was in accordance with distances of the (222) and (211) lattice planes of Mn2O3, respectively, indicating the presence of the Mn2O3 phase. Elemental mapping images (Figure 1c) showed that S atoms were distributed homogeneously. X-ray photoelectron spectroscopy (XPS) spectra of SO-Mn2O3 (Figure 1d) indicated that a peak assigned to S existed with an atomic ratio of 2.1%. The S 2p peak at 168.8 eV (Figure 1e) was assigned to SOₓ2− (x = 3, 4) [30,31]. X-ray diffraction (XRD) patterns (Figure 1f) confirmed that both samples had a bixbyite-type crystal structure (JCPDS no. 41-1442) with other impurities [20]. The above results verified the successful S incorporation into Mn2O3 via forming SOₓ2− species, and the crystal structure of Mn2O3 was well-maintained after S modification. The intensity of the diffraction peak for SO-Mn2O3 decreased compared to Mn2O3, and the peaks shifted toward lower angles, which were attributed to increased oxygen vacancies induced by sulfur modification [37,38].
The peaks at the binding energies of 641.15 eV, 642.43 eV, and 644.21 eV in XPS Mn 2p fine spectra of the Mn2O3 and SO-Mn2O3 samples (Figure 2a) were assigned to Mn(II), Mn(III), and Mn(IV), respectively [39]. Moreover, an increase in Mn(II) content and a decrease in Mn(IV) content in the SO-Mn2O3 sample compared to that of Mn2O3 indicated that the incorporation of S promoted an increase in low-valence manganese species. Previous studies have shown that the Mn4+-O bond is stronger than the Mn2+-O and Mn3+-O bonds [40]. Consequently, the presence of a large amount of low-valence Mn species weakened the Mn-O bond strength in SO-Mn2O3 [41]. The peaks at 341 cm−1 and 634 cm−1 in the Raman spectra of the Mn2O3 and SO-Mn2O3 samples (Figure 2b) were attributed to the deformation vibrations and lattice vibrations of the Mn-O-Mn and Mn-O bonds, respectively [42]. The results demonstrated that the transfer of electron cloud density from surface oxygen atoms in Mn2O3 to the electron-withdrawing SOx2− groups weakened their interaction with adjacent Mn atoms, thereby lengthening the Mn-O bond and reducing the bond strength, which is beneficial for lowering the energy barrier for the formation of Mn(V)=O species [41,43].
The N2 adsorption/desorption isotherms and corresponding structure characteristics (Figure 2c) obtained by the physical adsorption analyzer revealed that the specific surface area of SO-Mn2O3 (33.8 m2 g−1) is 2.2 times that of Mn2O3 (15.6 m2 g−1), indicating that SOx2− modification increases the specific surface area of the Mn2O3 catalyst, which could provide more adsorption and catalysis sites [37,38]. The hysteresis loop in the range of P/P0 between 0.8 and 1.0 suggested that the materials possess an aggregated pore structure, which is consistent with the TEM results.

3.2. Catalytic Performance of Mn2O3 and SO-Mn2O3

The catalytic performance of Mn2O3 and SO-Mn2O3 catalysts was evaluated by activating PMS for BPA degradation (Figure 3a). Before adding PMS, Mn2O3/BPA and SO-Mn2O3/BPA systems reached adsorption–desorption equilibrium within 10 min, with an adsorption ratio of approximately 6% (±0.026) and 14% (±0.031), respectively. The results are aligned with the fact that a larger specific surface area favors the adsorption of more pollutant molecules. In particular, PMS alone could hardly degrade BPA in the absence of a catalyst. The degradation ratio of BPA was only 29.9% (±0.036) within 10 min under the Mn2O3-activated PMS system. In contrast, the degradation rate of BPA exceeded 99.0% (±0.024) within 10 min under the SO-Mn2O3-activated PMS system. The degradation rate for BPA in the SO-Mn2O3/PMS system (0.434 min−1) was 15 times that of the Mn2O3/PMS system (0.029 min−1), as shown in the inset of Figure 3a. The mineralization rate within 10 min increased from 19.9% (±0.042) to 83.2% (±0.046) (Figure 3b). The above results indicated that SOx2− modification significantly enhanced the oxidation and mineralization capabilities of Mn2O3. Furthermore, the SO-Mn2O3 sample exhibited good cycling stability—the degradation ratio of BPA remained at 88.2% (±0.047) even after five consecutive cycles (Figure 3c). In addition, the SO-Mn2O3/PMS system demonstrated excellent oxidation capability for electron-rich phenolic organic pollutants, achieving degradation ratios of 99.8% (±0.024), 95.2% (±0.035), 94.4% (±0.041), and 92.5% (±0.038) for BPA, phenol, 4-CP, and 2,3-DP within 10 min, respectively (Figure 3d). Furthermore, the addition of Na+, Ca2+, Mg2+, Cl− (20 mM), SO42− (20 mM), and HCO3− (20 mM) had little effect on the BPA removal ratio (94%(±0.028)~99.2%(±0.008)), indicating strong resistance of the SO-Mn2O3/PMS system to interference from cations and anions (Figure 3e). Additionally, the removal ratio of BPA in lake water, tap water, and deionized water under the SO-Mn2O3/PMS system was 96.5% (±0.035), 96.4% (±0.036), and 99.2% (±0.024), respectively (Figure 3f), demonstrating the strong adaptability of the SO-Mn2O3/PMS system for catalytic degradation of BPA in real water bodies. The high selective oxidation of electron-rich pollutants, strong adaptability to real water bodies, and robust resistance to interference from anions and cations collectively demonstrated that a highly selective non-radical oxidation pathway dominated in the SO-Mn2O3/PMS system.

3.3. Catalytic Mechanism of the SO-Mn2O3/PMS System

To further verify the above conclusions, quenching experiments were conducted to identify the relative contributions of Mn(V)=O species, 1O2, SO4•−, and •OH. Tert-butanol (TBA), potassium thiocyanate (KSCN), methanol (CH3OH), sodium azide (NaN3), and potassium iodide (KI) were selected as scavengers for •OH, Mn(V)=O, SO4•−, 1O2, and surface-adsorbed SO4•− and •OH, respectively [9,11,15,44,45]. As shown in Figure S2, when TBA, KSCN, CH3OH, NaN3, and KI were added separately into the Mn2O3/PMS system, the degradation rate of BPA decreased from 29.9% (±0.036) to 23.7% (±0.029), 25.4% (±0.027), 11.9% (±0.023), 29.5% (±0.028), and 20.8% (±0.027), respectively. This indicated that the oxidative degradation of BPA under the Mn2O3/PMS system occurs through both radical and non-radical pathways, with the radical species (SO4•− and •OH) playing a dominant role. In the SO-Mn2O3/PMS system (Figure 4a), the presence of CH3OH, TBA, and KI had no effect on the BPA degradation ratio, while it reduced by 55.9% (±0.029) and 6.8% (±0.038) under the addition of KSCN and NaN3, respectively, indicating that the non-radical species high-valent Mn(V)=O and 1O2 played the dominant roles in BPA degradation.
Various probe compounds, including TPA, PMSO, HBA, and ABDA, were used to investigate the generation process of •OH, Mn(V)=O species, SO4•−, and 1O2, respectively [11,12,15,46]. In the Mn2O3/PMS system (Figure 4b), the characteristic fluorescence signal at 425 nm gradually increased with reaction time, while no significant change was observed in the SO-Mn2O3/PMS system (Figure 4c). This indicated that •OH was generated within the Mn2O3-activated PMS systems because it can react with TPA to form the fluorescent compound (2-hydroxyterephthalic acid), and no •OH was produced in the SO-Mn2O3/PMS system [46]. As obtained from Figure 4d,e, the intensity of the characteristic absorption peak for HBA gradually decreased with reaction time in the Mn2O3/PMS system, whereas it almost remained unchanged in the SO-Mn2O3/PMS system. This demonstrated the generation of SO4•− in the Mn2O3/PMS system and its absence in the SO-Mn2O3/PMS system [15]. It can be found from Figure 4f that the ratio of peak area for PMSO2/PMSO in the SO-Mn2O3/PMS system was 0.95, which is 16.4 times higher than that in the Mn2O3/PMS system (0.058), indicating that S-doped Mn2O3-activated PMS significantly enhanced the selective generation of Mn(V)=O species [11].
Additionally, the average oxidation state (AOS) of Mn species in SO-Mn2O3 before and after PMS activation was calculated using the formula AOS = 8.956 − 1.126 × ΔE, where ΔE represents the binding energy difference between the two peaks of Mn 3s [47,48]. The AOS values of SO-Mn2O3 before and after the activation were calculated to be 2.521 and 2.791, respectively, further proving an increase in surface high-valent manganese content after SO-Mn2O3 activating PMS (Figure 4g). Furthermore, in both the Mn2O3/PMS and SO-Mn2O3/PMS systems (Figure 4h,i), the characteristic absorption peak intensity of ABDA in the 300~450 nm range gradually decreased with reaction time, but the decrease was more significant in the SO-Mn2O3/PMS system within the same time period. This indicates that 1O2 is generated in both systems, but more is generated per unit time in the SO-Mn2O3/PMS system [15]. The above findings demonstrate that sulfur doping modulates the PMS activation pathway, not only suppressing radical generation but also promoting the formation of Mn(V)=O species and 1O2 for the selective oxidative degradation of electron-rich phenolic organic pollutants, thereby enhancing catalytic activity.

4. Conclusions

A highly active and selective SO-Mn2O3 solid catalyst was synthesized using a simple oxalate precipitation method and a calcination method. This catalyst was used to activate PMS for the efficient oxidation and mineralization of BPA. Within 10 min, the degradation rate of BPA exceeded 99.0%, with a reaction rate constant of 0.434 min−1 and a mineralization rate of BPA reaching 83.2% within 10 min. During the oxidative degradation of electron-rich phenolic pollutants by the SO-Mn2O3/PMS system, Mn(IV)=O species are the primary oxidizing species, and 1O2 also plays a certain role. The rapid and sustainable generation of stable Mn(IV)=O species simultaneously achieves high activity, high selectivity, and high stability for phenolic pollutant degradation, which is conducive to water purification applications.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/cryst15110922/s1, Figure S1: (a,b) TEM images of Mn2O3 samples; Figure S2: The BPA degradation ratio by Mn2O3/PMS system in the presence of TBA, KSCN, CH3OH, NaN3, and KI.

Author Contributions

Conceptualization, F.P. and X.Y.; methodology, F.P.; software, J.D.; validation, F.P., X.Y. and J.D.; formal analysis, J.D.; investigation, Y.X.; resources, F.P.; data curation, S.Y.; writing—original draft preparation, F.P.; visualization, Y.X. and J.D.; supervision, X.Y.; project administration, F.P. and S.Y.; funding acquisition, X.Y., Y.X. and F.P. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Scientific Research Program for Youth Innovation Teams of Shaanxi Provincial Department of Education (No. 24JP103), the Scientific Research Program Funded by the Education Department of Shaanxi Provincial Government (No. 23JP087), and Open Research Projects of Xi’an Key Laboratory for Monitoring and Prevention of Railway Track Subgrade and Bed Diseases (No. XJY24ZS007).

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

Author Jiajie Dong was employed by the company Qinchuan Machine Tool & Tool Group Co., Ltd.. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Crystals 15 00922 g001
Figure 1. (a,b) TEM images and (c) elemental mapping images of the SO-Mn2O3 sample. (d) XPS spectra of Mn2O3 and SO-Mn2O3 samples. (e) S 2p core-level spectrum of the SO-Mn2O3 sample. (f) XRD patterns of Mn2O3 and the SO-Mn2O3 sample.
Figure 1. (a,b) TEM images and (c) elemental mapping images of the SO-Mn2O3 sample. (d) XPS spectra of Mn2O3 and SO-Mn2O3 samples. (e) S 2p core-level spectrum of the SO-Mn2O3 sample. (f) XRD patterns of Mn2O3 and the SO-Mn2O3 sample.
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Figure 2. (a) XPS Mn 2p fine spectra, (b) Raman spectra, and (c) N2 adsorption–desorption isotherms of the Mn2O3 and SO-Mn2O3 samples.
Figure 2. (a) XPS Mn 2p fine spectra, (b) Raman spectra, and (c) N2 adsorption–desorption isotherms of the Mn2O3 and SO-Mn2O3 samples.
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Figure 3. (a) The catalytic performance and (b) the mineralization rate of Mn2O3/PMS and SO-Mn2O3/PMS for BPA degradation. Inset in (a) is the degradation rate. (c) Cyclic degradation performance of BPA by the SO-Mn2O3 sample. (d) The oxidation capability of the SO-Mn2O3/PMS system for bisphenol A, phenol, 4-chlorophenol, and 2,3-dichlorophenol within 10 min, respectively. (e) The effect of Na+, Ca2+, Mg2+, Cl− (20 mM), SO42− (20 mM), and HCO3− (20 mM) on the BPA removal ratio. (f) The removal ratio of BPA in lake water, tap water, and deionized water under the SO-Mn2O3/PMS system.
Figure 3. (a) The catalytic performance and (b) the mineralization rate of Mn2O3/PMS and SO-Mn2O3/PMS for BPA degradation. Inset in (a) is the degradation rate. (c) Cyclic degradation performance of BPA by the SO-Mn2O3 sample. (d) The oxidation capability of the SO-Mn2O3/PMS system for bisphenol A, phenol, 4-chlorophenol, and 2,3-dichlorophenol within 10 min, respectively. (e) The effect of Na+, Ca2+, Mg2+, Cl− (20 mM), SO42− (20 mM), and HCO3− (20 mM) on the BPA removal ratio. (f) The removal ratio of BPA in lake water, tap water, and deionized water under the SO-Mn2O3/PMS system.
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Figure 4. (a) The BPA degradation ratio by the SO-Mn2O3/PMS system in the presence of TBA, KSCN, CH3OH, NaN3, and KI. The characteristic fluorescence signal at 425 nm in the (b) Mn2O3/PMS system and (c) SO-Mn2O3/PMS system under probe compounds. The intensity of the characteristic absorption peak for HBA in the (d) Mn2O3/PMS system and (e) SO-Mn2O3/PMS system. (f) The ratio of peak area for PMSO2/PMSO in the Mn2O3/PMS system and SO-Mn2O3/PMS system. (g) XPS of Mn 3s spectra for SO-Mn2O3 sample before and after activation. The characteristic absorption peak intensity of ABDA is between 300 and 450 nm in the (h) Mn2O3/PMS system and (i) SO-Mn2O3/PMS system.
Figure 4. (a) The BPA degradation ratio by the SO-Mn2O3/PMS system in the presence of TBA, KSCN, CH3OH, NaN3, and KI. The characteristic fluorescence signal at 425 nm in the (b) Mn2O3/PMS system and (c) SO-Mn2O3/PMS system under probe compounds. The intensity of the characteristic absorption peak for HBA in the (d) Mn2O3/PMS system and (e) SO-Mn2O3/PMS system. (f) The ratio of peak area for PMSO2/PMSO in the Mn2O3/PMS system and SO-Mn2O3/PMS system. (g) XPS of Mn 3s spectra for SO-Mn2O3 sample before and after activation. The characteristic absorption peak intensity of ABDA is between 300 and 450 nm in the (h) Mn2O3/PMS system and (i) SO-Mn2O3/PMS system.
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Table 1. Instruments for sample characterization.
Table 1. Instruments for sample characterization.
InstrumentsFunctionsModelTesting Conditions
X-ray powder diffractometer (XRD)Phase compositions D8 Advance, Bruker, Ettlingen, Germany
Cu Kα radiation, λ = 0.15406 nm		Tube voltage: 40 kV, tube current: 40 mA, 2θ = 10~80°, step size: 0.020°, scanning speed: 5°/min
Transmission electron microscope (TEM)MicrostructuresJEM-2100, JEOL, Tokyo, JapanOperating voltage: 150 kV
Physical adsorption
analyzer		Specific surface areaASAP-2460, Micromeritics, Norcross, GA, USACarrier gas: N2
X-ray photoelectron spectroscopy (XPS)Surface chemical compositionK-Alpha, Thermo Fisher Scientific, Waltham, MA, USACalibrated via C 1s peak
Ultraviolet-visible spectrophotometerUltraviolet-visible spectroscopyU-3900, Hitachi, Tokyo, JapanTest wavelength range: 200~800 nm
Fluorescence spectrophotometerFluorescence spectrumRF-5301PC, Shimadzu, Kyoto, JapanExcitation wavelength: 412 nm, slit width: 2 nm
High-performance liquid chromatograph (HPLC)The concentration of organic compounds1100, Agilent, Santa Clara, CA, USA, Hypersil ODS C18 Columns, Column temperature: 40 °CDetection wavelengths: 254 nm,
mobile phase: acetonitrile and water (volume ratio 20:80), flow rate: 1 mL/min
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MDPI and ACS Style

Pei, F.; Dong, J.; Yan, X.; Xu, Y.; Yao, S. Efficient and Thorough Oxidation of Bisphenol A via Non-Radical Pathways Activated by SOx2−-Modified Mn2O3. Crystals 2025, 15, 922. https://doi.org/10.3390/cryst15110922

AMA Style

Pei F, Dong J, Yan X, Xu Y, Yao S. Efficient and Thorough Oxidation of Bisphenol A via Non-Radical Pathways Activated by SOx2−-Modified Mn2O3. Crystals. 2025; 15(11):922. https://doi.org/10.3390/cryst15110922

Chicago/Turabian Style

Pei, Fei, Jiajie Dong, Xin’e Yan, Youwen Xu, and Songyuan Yao. 2025. "Efficient and Thorough Oxidation of Bisphenol A via Non-Radical Pathways Activated by SOx2−-Modified Mn2O3" Crystals 15, no. 11: 922. https://doi.org/10.3390/cryst15110922

APA Style

Pei, F., Dong, J., Yan, X., Xu, Y., & Yao, S. (2025). Efficient and Thorough Oxidation of Bisphenol A via Non-Radical Pathways Activated by SOx2−-Modified Mn2O3. Crystals, 15(11), 922. https://doi.org/10.3390/cryst15110922

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