Next Article in Journal
Direct Vapour–Solid Synthesis of Intermetallic Pt-Zn and Pt-Te Nanoparticles on Carbon: Enhanced Oxygen Reduction Through Te and Zn Incorporation
Previous Article in Journal
Effects of Zeolite LTA Type and Humidity on Photocatalytic Ammonia Removal over TiO2-Coated Supports
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Catalysts
Volume 16
Issue 5
10.3390/catal16050460
catalysts-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Tunable Zn-Doping Enhanced Fenton-like Reaction for Butyl Xanthate Degradation: Unveiling the Non-Radical Reaction Pathway

by
Shaomeng Huang
1,2,
Yiqing Xu
1,
Feijian Jing
1,
Liping Wang
1,*,
Jiawen Sheng
1 and
Qiongqiong He
2
1
School of Environment Science and Spatial Informatics, China University of Mining and Technology, Xuzhou 221008, China
2
State Key Laboratory of Coking Coal Resources Green Exploitation, China University of Mining and Technology, Xuzhou 221116, China
*
Author to whom correspondence should be addressed.
Catalysts 2026, 16(5), 460; https://doi.org/10.3390/catal16050460
Submission received: 10 April 2026 / Revised: 4 May 2026 / Accepted: 12 May 2026 / Published: 14 May 2026
Editorial Note: Due to an editorial processing error, this article was incorrectly included within the Special Issue Catalytic Materials for Hazardous Wastewater Treatment upon publication. This article was removed from this Special Issue’s webpage on 21 May 2026 but remains within the regular issue in which it was originally published. The editorial office confirms that this article adhered to MDPI's standard editorial process (https://www.mdpi.com/editorial_process).
Browse Figures
Versions Notes

Abstract

In the process of pollutant degradation by activating peroxymonosulfate (PMS) with carbon-based Fenton-like catalysts containing Fe as the active site, the influence of Zn atoms on the system has rarely been studied. In this study, by regulating the introduction of Zn sources, Fe-Zn-C and Fe-C catalysts were successfully synthesized for activating PMS to degrade butyl xanthate (BX). The degradation experiment results showed that compared to the Fe-C system, the doping of Zn increased the degradation rate of BX in the Fe-Zn-C system by 10.66%, reaching 91.19% within 120 min. Moreover, by optimizing the reaction conditions, the highest BX degradation efficiency of 96.54% was achieved within 30 min. Through instrumental analysis, Fe and Zn elements were found to exist on the surface of the catalysts in the form of Fe2+Fe3+2O4 and ZnO crystals, and the catalytic oxidation reaction was dominated by non-free radical pathways, including 1O2 and direct electron transfer pathways. No free radicals were produced during the reaction, and it was speculated that Zn atoms played the role of an electron bridge in the reaction system, mediating electron transfer and enhancing catalytic performance through their synergistic effect with Fe. Comprehensive stability evaluation indicated that Fe-Zn-C ensures continuous catalytic activity and ecological safety with a low dissolution rate in aqueous solution. This study provides a new approach for the design of Fenton-like catalysts and the induction of non-radical pathways.

Graphical Abstract

1. Introduction

The global mining and mineral processing industry generates an enormous volume of wastewater annually. The discharge from mining and beneficiation operations in China reaches approximately 1.2–1.5 billion tons per year, and a substantial fraction of this effluent contains residual flotation reagents. Butyl xanthate (BX), the most widely employed collector in sulfide mineral flotation, is particularly concerning, as roughly 50% of the reagent remains in the wastewater stream [1,2,3]. Consequently, the development of efficient strategies for the degradation of xanthate in mineral processing wastewater is an urgent research priority.
A range of advanced oxidation processes (AOPs) are currently used for organic pollutant degradation, including ozonation, H2O2-based systems, peracetic acid oxidation, photocatalysis, electrochemical oxidation, and peroxymonosulfate (KHSO5, PMS)/peroxydisulfate (Na2S2O8, PDS) activation. Among these, persulfate-based systems offer distinct advantages, such as low cost, high efficiency, minimal secondary effects, strong oxidative capacity, broad applicability, independence from external energy input, and ease of long-distance transport [4,5]. Nevertheless, the intrinsic oxidizing power of persulfate alone is insufficient for the degradation of most recalcitrant organic pollutants. Upon appropriate activation, persulfate can generate sulfate radicals (OH• and SO4•−), which are highly electrophilic species capable of abstracting electrons from organic substrates, thereby inducing structural breakdown and even promoting complete mineralization under high dosage conditions [6]. Alternatively, singlet oxygen (1O2) may be generated during activation pathways, or degradation may proceed via direct electron transfer from pollutant molecules to PMS through the mediating effect of the catalyst surface, achieving organic pollutant degradation without radical intermediates.
Radical chain reactions exhibit notable advantages, particularly high selectivity toward electron-rich moieties such as phenolic groups, sulfides, and organic amines [7]. However, radicals are susceptible to scavenging by themselves and by co-existing inorganic ions, which not only diminishes oxidant utilization efficiency but may also generate toxic byproducts and secondary pollution [8]. In contrast, non-radical oxidation pathways are broadly categorized into direct electron transfer [9,10] and 1O2-mediated oxidation [11,12,13,14]. In the direct electron transfer mechanism, the persulfate adsorbed onto the catalyst surface accepts electrons and decomposes to form non-radical ionic species, while the pollutant donates electrons and undergoes oxidative degradation. The catalyst surface functions as an electron mediator, with no generation of free radicals or reactive oxygen species; this characteristic can effectively protect sensitive functional groups from non-selective attacks [9,10]. Compared with radical-based processes, non-radical degradation pathways offer distinct advantages: they exhibit high selectivity for electron-rich organic contaminants, remain unaffected by competing organic/inorganic constituents and radical scavengers, minimize undesirable side reactions, and achieve superior oxidant utilization efficiency [15,16,17]. Consequently, the investigation and deliberate engineering of non-radical pathways have attracted considerable research interest.
Currently, a broad spectrum of oxidants, including H2O2, PMS, PDS, peroxymonocarbonate, and peracetic acid, has been confirmed to be capable of following non-radical activation pathways. Of particular significance is the role of catalyst synthesis in steering the reaction toward these pathways [18,19,20,21,22]. The synthetic strategies reported thus far predominantly fall into two categories: (i) engineering the morphological, crystalline-phase, and defect structures of the catalyst, and (ii) incorporating alien atoms (metals or nonmetals) through atomic-scale elemental doping [23,24,25,26]. Certain carbonaceous materials and modified carbon analogues have been demonstrated to promote non-radical oxidation pathways in persulfate systems. Studies indicate that in carbon-activated PDS systems, a metastable surface complex forms between PDS and the carbon surface, facilitating direct electron transfer and SO42− generation while circumventing radical intermediates [27]. Alternatively, singlet oxygen can be generated to mediate oxidative degradation [28,29]. Hu et al. further advanced the direct electron transfer theory by demonstrating that electrons are transferred from active sites to surface-bound persulfate, forming a metastable state that subsequently abstracts electrons from adsorbed organic substrates to complete the oxidation reaction [30]. Additionally, defect sites in carbon frameworks have been shown to promote persulfate decomposition through steric and electronic effects, favoring singlet oxygen production, whereas edge sites can mediate direct electron transfer between pollutants and persulfate, leading to non-radical oxidation [31]. Shao et al. [32] synthesized vacancy-defective carbon nanotubes and proposed that these structures act as conductive bridges, facilitating electron transfer from high-energy occupied molecular orbitals of organic pollutants to low-energy unoccupied orbitals in PMS. DFT calculations further reveal that sp3- and sp2-hybridized carbon atoms at carbon edges enhance electron transfer with PMS, and that multilayered carbon architectures promote the transition from radical to non-radical pathways [33]. Heteroatom doping (e.g., B or S) of carbon materials introduces additional defect edge sites, modulates the local electron density of adjacent carbon atoms, and generates functional pyrrolic nitrogen, pyridinic nitrogen, and thiophenic sulfur species. These modifications enhance π-electron mobility through conjugation effects, thereby favoring non-radical-dominated oxidation reactions [34,35]. It can thus be inferred that surface defects in catalytic materials serve as critical structural motifs for steering oxidation pathways toward non-radical regimes.
Nevertheless, the electron transfer interactions among metals, non-metals, pollutants, active sites, and the catalyst framework in real reaction systems are inherently complex, rendering precise control over the catalytic oxidation pathway challenging. As a consequence, most catalytic degradation systems exhibit concurrent radical and non-radical mechanisms [36,37,38]. In this context, the present study aims to achieve the induction of an exclusive non-radical reaction pathway. Specifically, we investigate the synthesis of Fe-C catalysts with controlled Zn doping to enhance the efficiency of PMS activation for BX degradation. Advanced instrumental characterization is employed to elucidate the catalyst structure and the chemical states of the active sites. Degradation experiments are conducted to evaluate the influence of operational parameters on BX removal efficiency, catalyst activity, and stability. The mechanistic role of Zn doping in enhancing catalytic performance is systematically analyzed, the identity of reactive species generated within the system is determined, and the dominant reactive species governing the oxidation process is identified. Overall, this work contributes to the field of Fe-Zn atomic synergistic catalysis and the induction of non-radical pathways, offering new design concepts for the development of Fenton-like catalysts and the modulation of non-radical reactions.

2. Results and Discussion

2.1. Catalyst Characterization

FSEM-EDS analysis was used to conduct surface morphology and element distribution analysis of the catalysts. It can be observed that both Fe-Zn-C and Fe-C surfaces exhibit porous structures (Figure 1a,b). Among them, the pore structure of Fe-Zn-C is more developed than that of Fe-C, with larger pore sizes and a higher proportion of micrometer-sized pores. This is related to the addition of urea and the evaporation-induced pore formation during the heating process. The Fe-C surface mainly consists of stacked pores, with a sizes of less than 5 μm and relatively dense structures. Additionally, the Fe content of the Fe-Zn-C catalyst is 13.00%, which is lower than that of Fe-C (22.50%). The content and distribution of Fe and their influence on the catalytic oxidation activity are crucial. Moreover, the contents of C, N, and O elements are similar in both the Fe-Zn-C and Fe-C catalysts, but about 1.41% of Zn was doped into the Fe-Zn-C catalyst, while no Zn was added to Fe-C. Additionally, FeOx is hypothesized to exist based on the EDS surface scan images.
The XRD results of Fe-Zn-C and Fe-C catalysts are shown in Figure 2a. Six peaks are located at 30.10°, 35.42°, 43.05°, 56.94°, and 62.52°, which are assigned to the (2 2 0), (3 1 1), (4 0 0), (5 1 1), and (4 4 0) crystal planes of Fe2+Fe3+2O4 with the space group of Fd-3m (PDF#19-0629) [39]. In addition, the peaks centered at 31.77°, 36.25°, 47.54°, 56.60° and 62.86° belong to the Fe-C catalyst, which correspond to the (1 0 0), (1 0 1), (1 0 2), (1 1 0) and (1 0 3) planes of ZnO crystals with the space group of P63mc (PDF#36-1451) [40,41]. Fe2+Fe3+2O4 and ZnO are both detected in Fe-Zn-C catalysts, whereas only Fe2+Fe3+2O4 is found in Fe-C catalysts, which is consistent with the FSEM-EDS results. The intensity of the Fe2+Fe3+2O4 characteristic peaks in the Fe-Zn-C catalyst is higher than that of Fe-C, indicating a better crystallinity of Fe2+Fe3+2O4 in the Fe-Zn-C catalyst. Moreover, the broad peaks at about 25° can be ascribed to a disordered graphitized carbon structure [12,42,43]. Likewise, Raman spectroscopy was used to represent the defects (Figure 2b). The intensity ratio of the D band and the G band (ID/IG) is positively correlated with the number of defects. The ID/IG ratio of Fe-Zn-C is 2.82, which is higher than the value of 2.49 for Fe-C, demonstrating that the doping of Zn leads to the formation of more defects, thereby reducing the degree of graphitization [42].
FTIR is used to analyze the distribution of functional groups on the surface of the catalysts (Figure 2c). The peaks at 1080 cm−1 are attributed to the C-O/C-N bond, and the peak at about 1620 cm−1 is ascribed to the C=C bond, confirming the C/N/O skeleton of the catalysts [44,45]. Additionally, the peak at about 3440 cm−1 corresponds to the stretching vibration of the O-H bond, indicating the existence of a small amount of water on the surface of the catalyst [46]. The FTIR spectra of the two catalysts are similar, demonstrating that the surface functional groups are similar.
The specific surface area pore analyzer is used to characterize the pore size and distribution of the catalyst. N2 adsorption–desorption isotherms of the two catalysts are obtained with isotherms of type IV and hysteresis loops of type IV, which indicates the presence of both uneven and uniform slit-like pore structures and mesopores in both catalysts (Figure 2d) [47,48]. Figure 2e exhibits the total pore distribution and the micropore distribution. The average pore diameters of Fe-Zn-C and Fe-C catalysts are 6.41 and 21.02 nm, respectively, which are obtained through the BJH method. The average sizes of micropores of Fe-Zn-C and Fe-C catalysts are 0.86 and 1.13 nm (determined using the HK method), yet Fe-Zn-C has a significantly larger specific surface area of 37.09 m2/g, which is higher than that of Fe-C (21.76 m2/g), implying a larger surface for reaction during the catalytic process.
XPS is used to analyze the chemical states of various elements, and the results are shown in Figure 3. From Figure 3a–e, the C 1s peaks of the two catalysts at 284.8 eV, 285.9 eV, 287.3 eV, and 289.0 eV correspond to C-C, C-N, C-O, and C=O, respectively, which corresponds with the functional groups confirmed by FTIR. Moreover, the peak of N 1s at 399.1 eV corresponds to pyridinic N with contents of 41.39% and 43.37% for Fe-Zn-C and Fe-C, respectively. The peak at 401.1 eV is ascribed to graphitic N with contents of 58.61% and 56.63% for Fe-Zn-C and Fe-C, respectively [45]. Both N species can participate in the electron transfer process. Additionally, three different chemical states of oxygen in the two catalysts exist. For Fe-Zn-C, the O1s peaks at 530.3 eV, 531.9 eV, and 533.5 eV correspond to O-Fe/O-Zn, O=C, and O-C [44], respectively, confirming the existence of Fe2+Fe3+2O4 and ZnO by XRD. Importantly, the content of O-metal in Fe-Zn-C is 26.22%, which is 34.5% higher than that of the 19.49% for the Fe-C catalyst, demonstrating that the doping of Zn competes with Fe to consume O atoms and jointly form metal oxides. The binding energies of the peaks at 711.1 eV, 724.2 eV, 717.4 eV, and 730.5 eV correspond to Fe2+ 2p3/2, Fe2+ 2p1/2, and their satellite peaks, respectively, with similar contents of 72.62% and 71.68% in Fe-Zn-C and Fe-C. The binding energies of the peaks at 713.9 eV, 727.0 eV, 720.2 eV, and 733.3 eV correspond to Fe3+ 2p3/2, Fe3+ 2p1/2, and the satellite peaks with contents of 27.38% and 28.32% in Fe-Zn-C and Fe-C [44,46]. The redox cycle reaction of the Fe element is the key factor of the activity. The absence of a peak at 708.0 eV demonstrates the absence of Fe0 in both catalysts. In addition, the peaks at about 1021.5 eV and 1044.4 eV correspond to Zn2+ 2p3/2 and Zn2+ 2p1/2 for Fe-Zn-C catalysts [40,49]. The results confirm the elemental doping results of FTIR, FSEM-EDS, and XRD.

2.2. BX Degradation and Catalyst Evaluation

BX is widely used in mineral processing, and a certain amount of residue exists in the wastewater. In this study, BX was selected as the target pollutant, and the UV absorbance spectra are shown in Figure 4a. PMS was activated by Fe-Zn-C and Fe-C catalysts to oxidize and degrade BX. As can be seen from Figure 4b, the degradation rate of Fe-Zn-C within 120 min reaches 91.19%, which is 10.66% higher than that of the Fe-C system (80.53%), indicating that the doping of Zn is beneficial to the degradation of BX by the Fe-Zn-C/PMS system. Furthermore, the influence of different catalyst dosages of Fe-Zn-C on the reaction was investigated, and the results are shown in Figure 4c. As the catalyst dosage increases from 0.05 g/L to 0.1 g/L and then to 0.2 g/L, the degradation efficiency improves significantly from 72.72% to 84.21% and then to 91.19%, respectively. However, when the dosage increases to 0.3 g/L, the degradation reaction reaches equilibrium more quickly within 60 min, and the degradation efficiency slightly increases to 92.05%. This indicates that the appropriate increase in catalyst dosage can enhance the chemical reaction and degradation rates, which is related to an increase in catalytic reaction sites. Additionally, the influence of PMS concentration on the reaction of the Fe-Zn-C/PMS system was studied (Figure 4d). As the PMS concentration increases from 0.25 mM to 0.5 mM, 1 mM, and 2 mM, the reaction rate is significantly improved, and the degradation rate rises from 49.26% to 72.13%, 88.05% and 91.19%, respectively, indicating that as the concentration of PMS increases as the oxidant, the reaction rate becomes faster, more reactive species are produced, and the degradation rate of BX increases. Furthermore, the influence of the initial pH of the Fe-Zn-C/PMS/BX reaction system on the reaction process was also analyzed in this study. As shown in Figure 4e, the degradation rates of BX were 95.13%, 93.24%, 91.19%, and 65.42%, at initial pH values of 3, 5, 7, and 9, respectively. These results indicate that as the pH decreases, the degradation rate increases. However, when the pH is below 5, the degradation rate only increases slightly. This is related to the partial dissolution of Fe in acidic conditions and the occurrence of homogeneous catalytic reactions with higher efficiency. In this system, a highly efficient degradation process of BX can be maintained at a neutral pH of 7. Temperature also has a significant impact on the reaction rate. In this study, four experiments were conducted at temperatures of 10 °C, 20 °C, 30 °C, and 40 °C, and the degradation rates of BX were 52.46%, 71.14%, 91.19%, and 97.59%, respectively, indicating that the reaction temperature is positively correlated with the degradation rate of BX, and the reaction reaches equilibrium faster (Figure 4f). Additionally, the oxidation reaction almost reached equilibrium in 30 min at 40 °C, with a degradation rate of 96.54%, which is the best result in this study. BX degradation results by different catalysts in previous studies are shown in Table 1.
The cyclic experiments were conducted to study the stability of the Fe-Zn-C catalyst, and the results are shown in Figure 5a. Overall, the Fe-Zn-C catalyst did not show significant degradation after five cycles of experiments. The degradation rates of BX in the five experiments are 92.17%, 91.57%, 84.14%, 87.77%, and 86.13%, respectively. Compared with the first cycle, the degradation rate decreased by 0.60%, 8.03%, 4.40%, and 6.04%, respectively. Further, the concentrations of Fe dissolution during the five cycles of reactions were 346.4, 181.9, 67.8, 103.5, and 87.6 μg/L, while the concentrations of Zn dissolution were 637.1, 242.5, 185.7, 253.7, and 123.6 μg/L (Figure 5c), indicating that the catalyst has good stability, and its low metal dissolution rate determines the low activity attenuation in the five-cycle experiments. More importantly, the mineralization rates of BX in the five-cycle experiments were 26.8%, 35.5%, 46.2%, 49.8%, and 45.8%, showing an increasing trend. It is speculated that this may be due to the exposure of more active sites and the generation of more active species as reaction times increase, resulting in more thorough degradation of BX (Figure 5d). Additionally, to investigate the reaction activity of the Fe-Zn-C catalyst in the high-concentration anion environment, a series of co-existing anions were set up. As can be seen from Figure 5b, the addition of Cl−, CO32−, HPO42−, and NO3− had a relatively small impact on the reaction. Among them, the degradation rates of BX in the Cl−, CO32−, and NO3− solutions were 86.19%, 87.51%, and 77.76%, respectively, which were 5.00%, 3.68%, and 13.43% lower than that of the 91.19% of the control experiment. It is speculated that this may be due to the consumption of free radicals in the chain reaction with the anions. However, the introduction of HPO42− increased the degradation rate of BX to 92.36%, which may be related to the hydrolysis process. In conclusion, the Fe-Zn-C catalyst has strong stability and salt resistance.

2.3. Identification of ROS

To determine the contributions of various reactive oxygen species to the catalytic oxidation process, quenching experiments were carried out. Briefly, MeOH can serve as a quencher for OH• and SO4•−, while tert-butyl alcohol (TBA) has a higher quenching reaction rate for OH• (k = 3.8 × 109 M−1 s−1–7.6 × 109 M−1 s−1). FFA is an effective quencher of 1O2 with a k value of 1.2 × 108 M−1 s−1. p-Benzoquinone (p-BQ) can act as a quencher for O2•− (k = 9.7 × 108 M−1 s−1) [13,14]. As shown in Figure 6a, the BX degradation processes in the Fe-Zn-C-PMS system were inhibited by adding MeOH, TBA, FFA, and p-BQ, leading to a decrease in the removal efficiency within 120 min from 91.19% to 55.61%, 51.65%, 30.65%, and 68.42%, respectively. Similarly, the degradation rate in the Fe-C-PMS system reduced from 80.53% to 69.46%, 58.15%, 23.17%, and 54.75%, respectively (Figure 6b). These results indicate that 1O2 played an important role in the reaction process. To further investigate the reactive species, quenching experiments with different quencher concentrations were conducted in the Fe-Zn-C-PMS system, which performs better than the Fe-C-PMS system (Figure 6c–f). As the concentration of MeOH increased from 0 mM to 100, 200, 500, and 1000 mM, the degradation rate of BX decreased from 91.19% to 64.32%, 51.96%, 53.33%, and 55.61% within 120 min. As the TBA concentration increased from 0 mM to 100, 200, 500, and 1000 mM, the degradation rate of BX decreased from 91.19% to 71.33%, 59.46%, 61.69%, and 51.65%, indicating that OH• was generated and participated in the oxidation reaction. As the FFA concentration increased from 0 mM to 100, 200, 500, and 1000 mM, the degradation rate of BX within 120 min decreased from 91.19% to 39.23%, 34.92%, 37.23%, and 30.65%, indicating that 1O2 was produced in large quantities and dominated the process. As the p-BQ concentration increased from 0 mM to 1 mM, 2 mM, 5 mM, and 10 mM, the degradation rate of BX decreased from 91.19% to 72.35%, 66.51%, 74.32%, and 68.42%, respectively, indicating that O2•− was fully involved in the reaction. In conclusion, the participation of 1O2 and O2•− was dominant, while OH• also participated in some of the reactions.
ESR is typically used for direct qualitative analysis of reactive species. It mainly achieves the chelation reaction with active species by using chelating agents, thereby generating detectable intermediates. The commonly used capture agents are DMPO and TEMP. DMPO can react with OH• and SO4•−, leading to the generation of DMPO-OH•. TEMP can react with 1O2, generating TEMP-1O2. From Figure 7a,c, it can be observed that neither the Fe-Zn-C/PMS nor the Fe-C/PMS system produced OH• and SO4•−. Importantly, DMPOX, the product obtained by direct oxidation with DMPO, was detected, and the intensity increased with time, revealing the existence of a direct electron transfer pathway, which exists in both catalyst systems, rather than a free radical reaction [13,14]. More importantly, Figure 7b,d shows that 1O2 was extensively generated in both systems [55,56]. The signal of TEMP-1O2 became stronger as time went on. These results confirm that the 1O2 species is the active species that dominates the oxidation reaction, which is consistent with the results of the quenching experiments.

2.4. Catalytic Mechanism

By identifying the active species, the reaction mechanism of BX and PMS on the Fe-Zn-C catalyst surface can be inferred. Fe2+Fe3+2O4 and ZnO are dispersed on the C-N network as shown in Figure 8, which was obtained through FSEM-EDS and XRD analyses. Two types of the BX oxidation pathways are speculated. Firstly, both BX and PMS are adsorbed on the surface of the active site. Through the driving force of the potential difference, electrons are lost from BX, causing the breaking of the C-O bond, and BX is decomposed into CS2 and C3H9O. The C-C and C-O bonds in C3H9O are further attacked and then mineralized into CO2 and H2O. The electrons are transferred from Fe atoms in the Fe2+Fe3+2O4 crystal and the Zn atoms in the ZnO crystal to the adsorbed HSO5−, mediated by the O atoms and the C-N surface in the process. The O-O bond of PMS gains a sufficient number of electrons, leading to the decomposition of PMS with the generation of SO42− and OH−. Direct electron transfer between the BX active site and PMS occurs in this process, which is named the direct electron transfer pathway and does not produce free radicals. Additionally, part of PMS is adsorbed on the Fe atoms of the Fe2+Fe3+2O4 crystal, and after obtaining part of the electrons, the O-O bond and O-H bond break, resulting in the generation of an Fe-O intermediate. The O atom can react with another O atom to generate 1O2 after the desorption. 1O2 has strong oxidizing properties and a longer lifetime than free radicals, and it can directly attack multiple chemical bonds of BX, thereby leading to the decomposition and mineralization. This is named the 1O2 pathway. Moreover, from the degradation experiments, it can be seen that the catalytic ability of the Fe-Zn-C catalyst is higher than that of the Fe-C catalyst. Therefore, it is inferred that during the reaction process, the Zn atom can also act as an electron bridge to mediate the transfer of electrons, and its synergy with Fe strengthens the catalytic ability.
In conclusion, it was established that the decomposition of BX proceeded primarily through a mechanism governed by direct electron transfer coupled with 1O2. The Zn atoms are proposed to act as electronic conduits, shuttling electrons and thereby substantially enhancing the catalytic performance.

3. Materials and Methods

3.1. Chemicals

The polystyrene butadiene copolymer, CH2Cl2, Fe(NO3)3·9H2O, Zn(NO3)2·6H2O, urea, HCl, 2KHSO5·KHSO4·K2SO4 (PMS), furfuryl alcohol (FFA), methanol (MeOH), tert-butanol (TBA), p-benzoquinone (p-BQ), NaCl, NaNO3, Na2CO3, Na2HPO4·12H2O and Na2S2O3 were of pure analytical grade and obtained from Xilong Scientific Co., Ltd. (Shantou, China) and Aladdin (Shanghai, China).

3.2. Catalyst Preparation

A large number of used rubber products need to be disposed of as rubber ages, especially tires, so the utilization of waste rubber is of great significance. In this study, styrene-butadiene rubber was used as the precursor for the synthesis of the catalyst framework. By adjusting the doping of Fe, Zn, and N elements and pore formation, the Fe-Zn-C and Fe-C catalysts were synthesized, aiming to explore the utilization methods of waste styrene-butadiene rubber and investigate the influence of Zn atoms on the catalytic performance of the system.
Briefly, 10 g of styrene-butadiene rubber was cut into pieces and dissolved in 500 mL of CH2Cl2. Then the mixture was stirred magnetically under sealed conditions using plastic wrap for 2 h. In order to facilitate dissolution, the residual particles were crushed, and the stirring was continued for another 2 h until complete dissolution. Then 4.04 g of Fe(NO3)3·9H2O, 2.97 g of Zn(NO3)2·6H2O, and 1.2 g of urea were added to the solution, and stirring was continued while the temperature rose to 50 °C until the liquid completely evaporated. Next, the residue was scraped off and loaded into alumina crucibles without lids to maintain contact with air, and then carbonized in a tubular furnace under 99% purity N2. The heating procedure was as follows: The temperature was raised at a rate of 5 °C/min to 300 °C and maintained for 2 h. Then, the temperature was increased at the same rate to 800 °C and maintained for 2 h. Finally, the furnace was cooled to room temperature. Next, the solid was washed using HCl (0.1 M) and deionized water several times, respectively, and then dried under vacuum at 105 °C to obtain Fe-Zn-C. The above process was repeated without adding Zn(NO3)2·6H2O to avoid Zn doping, and the Fe-C catalyst was obtained.

3.3. Characterization

The morphology and surface elemental distribution of Fe-Zn-C and Fe-C were examined using field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (FSEM-EDS, GeminiSEM 300, ZEISS, Oberkochen, Germany). The mineralogical composition and crystal structure were characterized by X-ray diffraction (XRD, D8 ADVANCE, Bruker, Karlsruhe, Germany). The surface chemical states of the catalysts were analyzed by X-ray photoelectron spectroscopy (XPS, Kratos AXIS Ultra DLD, Shimadzu, Kyoto, Japan). Nitrogen adsorption–desorption isotherms, specific surface area, and pore size distribution were determined using a surface area and porosimetry analyzer (ASAP2460, Micromeritics, Norcross, GA, USA). Functional groups present on the catalyst surface were identified by Fourier-transform infrared spectroscopy (FTIR, Nicolet iS5, Thermo Fisher, Waltham, MA, USA).

3.4. Experimental Procedures

The experiments were conducted in a 250 mL flask in a shaker at 100 rpm. Specifically, the influence of elements (Fe-Zn-C and Fe-C), catalyst dosage (i.e., 0.05, 0.1, 0.2, and 0.3 g/L), PMS concentration (i.e., 0.25, 0.5, 1, and 2 mM), temperature (i.e., 10, 20, 30, and 40 °C), initial pH (i.e., 3, 5, 7, and 9), co-existing anions (i.e., Cl−, NO3−, and CO32−, HPO42−), and the cycling performance were investigated. In addition, different concentrations of MeOH, TBA, FFA, and p-BQ were used to quench the catalytic oxidation reaction, thereby investigating the reactive species generated during the reaction and their respective contributions. During the experiments, samples were taken out according to the scheduled time, and an excess amount of Na2S2O3 was used to quench the reactions. The sample solutions were then filtered through a 0.22 μm inorganic membrane before ultraviolet spectrophotometer analysis.

3.5. Analytical Methods

The concentration of BX was analyzed via an ultraviolet spectrophotometer (4802s UV/VIS, Unico, Shanghai, China) with a detection wavelength of 300.5 nm. The leaching of Fe and Zn during the reaction was measured using ICP-MS (Agilent 7800MS, Agilent, Santa Clara, CA, USA). To determine the mineralization rate of BX in the reaction system, a total organic carbon/total nitrogen analyzer (TOC-L TNM-L CSN, Shimadzu, Japan) was used to analyze the solution after the reaction. An electron spin resonance spectrometer (ESR5000, Bruker, Germany) was used to capture the active radicals using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and 2,2,6,6-tetramethyl-4-piperidone (TEMP) as trapping agents.

4. Conclusions

Fe-Zn-C and Fe-C catalysts were successfully fabricated to activate PMS for the degradation of BX. The results demonstrated excellent catalytic activity with a non-free radical pathway. A total of 91.19% of BX was eliminated in 120 min in the Fe-Zn-C system, which is 10.66% higher than that of the Fe-C system (80.53%), indicating the better catalytic ability of Fe-Zn-C, which exhibits the best performance with 96.54% of BX degradation in 30 min at 40 °C. Through FSEM-EDS, XRD, FTIR, and XPS analyses, it was found that Fe2+Fe3+2O4 and ZnO crystals exist in the Fe-Zn-C catalyst, which serve as active sites. The quenching experiment and ESR analysis revealed that in the Fe-Zn-C-PMS system, 1O2 was mainly generated, and no free radicals were formed. Thus, the reaction mechanism was determined to be dominated by direct electron transfer and the 1O2 reaction pathway in the degradation of BX. The Zn atom was speculated to serve as an electron bridge to mediate the transfer of electrons, which strengthened the catalytic ability. A comprehensive stability evaluation indicated that Fe-Zn-C ensures the ecological safety with a low dissolution rate in aquatic environments. This work has developed a new catalyst for BX degradation and has also provided a new idea for inducing non-free radical reaction pathways through catalyst design.

Author Contributions

S.H.: Conceptualization, formal analysis, data curation, methodology, writing—original draft. Y.X. and Q.H.: data curation, investigation, visualization, software. L.W. and J.S.: conceptualization, funding acquisition, supervision, project administration, writing—review and editing. F.J.: validation, writing—review and editing. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the National Natural Science Foundation of China (Grant No. 52504320), the Basic Research Program of Jiangsu (BK20251636), Jiangsu Funding Program for Excellent Postdoctoral Talent (2024ZB724), and the Fundamental Research Funds for the Central Universities (2025QN1107).

Data Availability Statement

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

Acknowledgments

We are grateful to the editors and anonymous reviewers for their valuable comments and suggestions for our paper.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Fu, P.; Wang, L.; Li, G.; Hou, Z.; Ma, Y. Homogenous catalytic ozonation of aniline aerofloat collector by coexisted transition metallic ions in flotation wastewaters. J. Environ. Chem. Eng. 2020, 8, 103714. [Google Scholar] [CrossRef] [Scilit]
  2. Wang, X.; Chen, M.; Ma, L.; Juholin, P.; Sapsford, D.J. Degradation of residual xanthates in mineral processing wastewater—A review. Miner. Eng. 2024, 212, 108717. [Google Scholar] [CrossRef] [Scilit]
  3. Sun, S.; Ren, M.; Pan, F.; Yuan, L.; Ning, P.; Sun, Z.; Xie, Y.; Cao, H. Degradation of potassium alkyl xanthogenate in wet air oxidation: Enhancement method, degradation mechanism and structure impact. J. Environ. Chem. Eng. 2022, 10, 107349. [Google Scholar] [CrossRef] [Scilit]
  4. Duan, X.; Sun, H.; Kang, J.; Wang, Y.; Indrawirawan, S.; Wang, S. Insights into heterogeneous catalysis of persulfate activation on dimensional-structured nanocarbons. ACS Catal. 2015, 5, 4629–4636. [Google Scholar] [CrossRef] [Scilit]
  5. Wacławek, S.; Lutze, H.; Grübel, K.; Padil, V.V.T.; Dionysiou, D.D. Chemistry of persulfates in water and wastewater treatment: A review. Chem. Eng. J. 2017, 330, 44–62. [Google Scholar] [CrossRef] [Scilit]
  6. Peyton, G.R. The free-radical chemistry of persulfate-based total organic carbon analyzers. Mar. Chem. 1993, 41, 91–103. [Google Scholar] [CrossRef] [Scilit]
  7. Wang, C.; Kang, J.; Liang, P.; Zhang, H.; Sun, H.; Tadé, M.O.; Wang, S. Ferric carbide nanocrystals encapsulated in nitrogen-doped carbon nanotubes as an outstanding environmental catalyst. Environ. Sci. Nano 2017, 4, 170–179. [Google Scholar] [CrossRef] [Scilit]
  8. Xu, L.; Yuan, R.; Guo, Y.; Xiao, D.; Cao, Y.; Wang, Z.; Liu, J. Sulfate radical-induced degradation of 2,4,6-trichlorophenol: A de novo formation of chlorinated compounds. Chem. Eng. J. 2013, 217, 169–173. [Google Scholar] [CrossRef] [Scilit]
  9. Li, H.; Shan, C.; Pan, B. Fe(III)-doped g-C3N4 mediated peroxymonosulfate activation for selective degradation of phenolic compounds via high-valent iron-oxo species. Environ. Sci. Technol. 2018, 52, 2197–2205. [Google Scholar] [CrossRef] [Scilit]
  10. Li, H.; Tian, J.; Xiao, F.; Huang, R.; Gao, S.; Cui, F.; Wang, S.; Duan, X. Structure-dependent catalysis of cuprous oxides in peroxymonosulfate activation via nonradical pathway with a high oxidation capacity. J. Hazard. Mater. 2020, 385, 121518. [Google Scholar] [CrossRef] [Scilit]
  11. Zhu, S.; Li, X.; Kang, J.; Duan, X.; Wang, S. Persulfate activation on crystallographic manganese oxides: Mechanism of singlet oxygen evolution for nonradical selective degradation of aqueous contaminants. Environ. Sci. Technol. 2019, 53, 307–315. [Google Scholar] [CrossRef] [Scilit]
  12. Gao, Y.; Wu, T.; Yang, C.; Ma, C.; Zhao, Z.; Wu, Z.; Cao, S.; Geng, W.; Wang, Y.; Yao, Y. Activity trends and mechanisms in peroxymonosulfate-assisted catalytic production of singlet oxygen over atomic metal-N-C catalysts. Angew. Chem. Int. Ed. 2021, 60, 22513–22521. [Google Scholar] [CrossRef] [Scilit] [PubMed]
  13. Li, W.; Cai, X.; Zhou, X.; Luo, Z.; Yan, C.; Ge, J.; Huang, Z.; Zhang, Y.; Wang, P.; Luo, Y.; et al. Morphology-coordination dual engineering in cobalt single-atom catalysts: Steering peroxymonosulfate activation into selective 1O2 generation for efficient antibiotic degradation. Appl. Catal. B Environ. Energy 2026, 382, 125933. [Google Scholar] [CrossRef] [Scilit]
  14. Wu, Y.; Hao, C.; Lu, Z.; Liu, X.; Jiang, W.; Zhou, L.; Wang, X.; Zhou, L.; Lei, J.; Zhang, J.; et al. Tailoring COFs for highly selective generation of singlet oxygen to boost antibiotic removal: Spatial regulation of PMS and photogenerated carriers. Water Res. 2026, 297, 125653. [Google Scholar] [CrossRef] [Scilit]
  15. Duan, X.; Sun, H.; Shao, Z.; Wang, S. Nonradical reactions in environmental remediation processes: Uncertainty and challenges. Appl. Catal. B Environ. 2018, 224, 973–982. [Google Scholar] [CrossRef] [Scilit]
  16. Ahn, Y.Y.; Yun, E.T.; Seo, J.W.; Lee, C.; Kim, S.H.; Kim, J.H.; Lee, J. Activation of peroxymonosulfate by surface-loaded noble metal nanoparticles for oxidative degradation of organic compounds. Environ. Sci. Technol. 2016, 50, 10187–10197. [Google Scholar] [CrossRef] [Scilit] [PubMed]
  17. Zhang, T.; Chen, Y.; Wang, Y.; Roux, J.L.; Yang, Y.; Croue, J.P. Efficient peroxydisulfate activation process not relying on sulfate radical generation for water pollutant degradation. Environ. Sci. Technol. 2014, 48, 5868–5875. [Google Scholar] [CrossRef] [Scilit]
  18. Wu, Z.; Xiong, Z.; Huang, B.; Yao, G.; Zhan, S.; Lai, B. Long-range interactions driving neighboring Fe–N4 sites in Fenton-like reactions for sustainable water decontamination. Nat. Commun. 2024, 15, 7775. [Google Scholar] [CrossRef] [Scilit]
  19. Ma, C.; Wang, J.; Liu, X.; Duan, X.; Qi, J.; Li, S.; Li, N.; Li, Y.; Fan, X.; Peng, W. Enhanced Fe(III)/Fe(II) cycle by lattice sulfur for continuous fenton reactions. Environ. Sci. Technol. 2025, 59, 8812–8821. [Google Scholar] [CrossRef] [Scilit]
  20. Luo, X.; Li, Y.; Ma, X.; Sen, T.; Zhao, L.; Yang, Y.; Sun, P. Enhanced norfloxacin oxidation with an Fe(VI)/peroxydisulfate-quinone process: Iron species-driven multi-oxidation, quinone-based regulation, and density functional theory analysis. Water Res. 2026, 289, 124850. [Google Scholar] [CrossRef] [Scilit]
  21. Yang, Z.; Zhou, Y.; Jiang, Y.; Zhao, P.; Meng, X. Reconsideration of the role of hydrogen peroxide in peroxymonocarbonate-based oxidation system for pollutant control. Water Res. 2025, 268, 122750. [Google Scholar] [CrossRef] [Scilit]
  22. Chen, L.; Zhang, R.; Liu, Z.; Sun, W.; Li, F.; Shen, Z.; Liu, W. Identification and transformation of reactive species in peracetic acid catalytic activation systems using in situ electron paramagnetic resonance. Environ. Sci. Technol. 2025, 59, 21365–21378. [Google Scholar] [CrossRef] [Scilit]
  23. Cai, J.; Wan, J.; Wang, Y.; Yi, J.; Liang, Y. Developing a β-cyclodextrin modified nanoconfined channels catalyst for efficient activation of peroxymonosulfate: Enhancing non-radical pathways and electron transfer. Appl. Catal. B Environ. Energy 2025, 375, 125401. [Google Scholar] [CrossRef] [Scilit]
  24. Ning, Z.; Tan, X.; Wei, Q.; Liu, Y.; Wang, R.; Guo, H.; Ren, J.; Ma, Q.; Zhou, J.; Wang, T. Rapid charge transfer and non-radical pathways induced by nanoconfined Fe species/S(IV) system realized complete sulfadiazine degradation. Appl. Catal. B Environ. Energy 2026, 380, 125761. [Google Scholar] [CrossRef] [Scilit]
  25. Chen, Z.; Zhao, C.; Ma, R.; Yao, Z.; Guo, Z.; Zhao, Z.; Zheng, Y.; Fu, H. Interface and polarization engineering of ZIF-67(Co)-based heterojunctions for selective non-radical PMS activation: Simultaneous generation of 1O2 and Co(IV)=O for efficient and safe water remediation. Adv. Funct. Mater. 2025, 36, e16474. [Google Scholar] [CrossRef] [Scilit]
  26. Li, X.; Gao, Y.; Qi, J.; Liu, Y.; Li, Q.; Wang, J.; Wang, L. Asymmetric coordination modulating Co spin state for peroxymonosulfate activation to accelerate 1O2 generation. Adv. Funct. Mater. 2025, 35, 2502680. [Google Scholar] [CrossRef] [Scilit]
  27. Guan, C.; Jiang, J.; Luo, C.; Pang, S.; Jiang, C.; Ma, J.; Jin, Y.; Li, J. Transformation of iodide by carbon nanotube activated peroxydisulfate and formation of iodoorganic compounds in the presence of natural organic matter. Environ. Sci. Technol. 2017, 51, 479–487. [Google Scholar] [CrossRef] [Scilit] [PubMed]
  28. Yun, E.T.; Lee, J.H.; Kim, J.; Park, H.D.; Lee, J. Identifying the nonradical mechanism in the peroxymonosulfate activation process: Singlet oxygenation versus mediated electron transfer. Environ. Sci. Technol. 2018, 52, 7032–7042. [Google Scholar] [CrossRef] [Scilit]
  29. Cheng, X.; Guo, H.; Zhang, Y.; Wu, X.; Liu, Y. Non-photochemical production of singlet oxygen via activation of persulfate by carbon nanotubes. Water Res. 2017, 113, 80–88. [Google Scholar] [CrossRef] [Scilit] [PubMed]
  30. Hu, P.; Su, H.; Chen, Z.; Yu, C.; Li, Q.; Zhou, B.; Alvarez, P.J.J.; Long, M. Selective degradation of organic pollutants using an efficient metal-free catalyst derived from carbonized polypyrrole via peroxymonosulfate activation. Environ. Sci. Technol. 2017, 51, 11288–11296. [Google Scholar] [CrossRef] [Scilit]
  31. Cheng, X.; Guo, H.; Zhang, Y.; Korshin, G.V.; Yang, B. Insights into the mechanism of nonradical reactions of persulfate activated by carbon nanotubes: Activation performance and structure-function relationship. Water Res. 2019, 157, 406–414. [Google Scholar] [CrossRef] [Scilit] [PubMed]
  32. Shao, P.; Yu, S.; Duan, X.; Yang, L.; Shi, H.; Ding, L.; Tian, J.; Yang, L.; Luo, X.; Wang, S. Potential difference driving electron transfer via defective carbon nanotubes toward selective oxidation of organic micropollutants. Environ. Sci. Technol. 2020, 54, 8464–8472. [Google Scholar] [CrossRef] [Scilit]
  33. Duan, X.; Ao, Z.; Zhang, H.; Saunders, M.; Sun, H.; Shao, Z.; Wang, S. Nanodiamonds in sp2 /sp3 configuration for radical to nonradical oxidation: Core-shell layer dependence. Appl. Catal. B Environ. 2018, 222, 176–181. [Google Scholar] [CrossRef] [Scilit]
  34. Wang, Y.; Liu, M.; Zhao, X.; Cao, D.; Guo, T.; Yang, B. Insights into heterogeneous catalysis of peroxymonosulfate activation by boron-doped ordered mesoporous carbon. Carbon 2018, 135, 238–247. [Google Scholar] [CrossRef] [Scilit]
  35. Guo, Y.; Zeng, Z.; Zhu, Y.; Huang, Z.; Cui, Y.; Yang, J. Catalytic oxidation of aqueous organic contaminants by persulfate activated with sulfur-doped hierarchically porous carbon derived from thiophene. Appl. Catal. B Environ. 2018, 220, 635–644. [Google Scholar] [CrossRef] [Scilit]
  36. Gao, D.; Lu, Y.; Chen, Y.; Bao, M.; Xu, N. Novel CoFe2Px derived from CoFe2O4 for efficient peroxymonosulfate activation: Switching the reaction route and suppressing metal leaching. Appl. Catal. B Environ. 2022, 309, 121234. [Google Scholar] [CrossRef] [Scilit]
  37. Gao, Y.; Chen, Z.; Zhu, Y.; Li, T.; Hu, C. New insights into the generation of singlet oxygen in the metal-free peroxymonosulfate activation process: Important role of electron-deficient carbon atoms. Environ. Sci. Technol. 2020, 54, 1232–1241. [Google Scholar] [CrossRef] [Scilit] [PubMed]
  38. Zhong, Q.; Xu, C.; Liu, Y.; Ji, Q.; Xu, Z.; Sun, D.; Zhou, S.; Yang, B.; Dai, Y.; Qi, C.; et al. Defect-engineered FeSe2−x@C with porous architecture for enhanced peroxymonosulfate-based advanced oxidation processes. Appl. Catal. B Environ. 2022, 309, 121259. [Google Scholar] [CrossRef] [Scilit]
  39. Mirzaee, R.; Darvishi Cheshmeh Soltani, R.; Khataee, A.; Boczkaj, G. Combination of air-dispersion cathode with sacrificial iron anode generating Fe2+Fe3+2O4 nanostructures to degrade paracetamol under ultrasonic irradiation. J. Mol. Liq. 2019, 284, 536–546. [Google Scholar] [CrossRef] [Scilit]
  40. Zhou, Z.; Pourhashem, S.; Wang, Z.; Duan, J.; Zhang, R.; Hou, B. Distinctive roles of graphene oxide, ZnO quantum dots, and their nanohybrids in anti-corrosion and anti-fouling performance of waterborne epoxy coatings. Chem. Eng. J. 2022, 439, 135765. [Google Scholar] [CrossRef] [Scilit]
  41. Pandey, S.K.; Mishra, P.K.; Tiwary, D. Enhanced photocatalytic performance of NiS/ZnO nanocomposite for the remediation of PNP and RhB dye. J. Environ. Chem. Eng. 2022, 10, 107459. [Google Scholar] [CrossRef] [Scilit]
  42. Niu, Y.; Li, X.; Dong, W.; Zhang, C.; Zhao, K.; Wang, F.; Wang, H. Synthesis of N-doped carbon with embedded Fe/Fe3C particles for microwave absorption. J. Mater. Sci. 2020, 55, 11970–11983. [Google Scholar] [CrossRef] [Scilit]
  43. Kumari, P.K.; Rao, B.S.; Lingaiah, N. Selective transformation of carbohydrates to 5-ethoxymethylfurfural over tungstophosphoric acid supported on activated carbon derived from orange peel. J. Indian Chem. Soc. 2023, 100, 101007. [Google Scholar] [CrossRef] [Scilit]
  44. Zhu, Z.; Jiang, Y.; Xu, L.; An, Q.; Nga, T.T.T.; Chen, J.; Fan, Y.; Liu, Q.; Dong, C.-L.; Wang, S.; et al. Highly efficient synthesis of α-amino acids via electrocatalytic C-N coupling reaction over an atomically dispersed iron loaded defective TiO2. Adv. Mater. 2025, 37, 2409864. [Google Scholar] [CrossRef] [Scilit]
  45. Wu, Q.; Wu, L.; Han, Y.; Zou, H.; Su, X.; Chu, Y.; Deng, H.; Tang, S.; Wang, X.; Zhang, D.; et al. Spatially matched C–N coupling within carbon defect confined interlayer Fe clusters for efficient urea electrosynthesis. Adv. Mater. 2026, 38, e14503. [Google Scholar] [CrossRef] [Scilit]
  46. Guo, T.; Bulin, C.; Zheng, R. Fabrication of ion imprinted diethylenetriamine pentaacetic acid-polyethylenimine modified magnetic graphene oxide for selective adsorption of Ce(III). J. Clean. Prod. 2024, 481, 144104. [Google Scholar] [CrossRef] [Scilit]
  47. Wang, T.; Hu, Q.; Yang, X.; Wang, Q.; Li, S. Water vapor adsorption characteristics and controlling factor analyses in permian-aged organic-rich marine gufeng and dalong formations in northeastern chongqing area of China. ACS Omega 2026, 11, 19811–19826. [Google Scholar] [CrossRef] [Scilit] [PubMed]
  48. Wogo, H.E.; Silmi, N.; Benu, D.P.; Steky, F.V.; Setiawan, K.M.; Sudirman; Azzindani, M.W.; Mukti, R.R.; Suendo, V. Investigating the correlation of morphology with the N2 physisorption behavior of Al-incorporated bcl silica. Langmuir 2025, 41, 5794–5807. [Google Scholar] [CrossRef] [Scilit]
  49. Su, G.; Feng, T.; Huang, Z.; Zheng, Y.; Zhang, W.; Liu, G.; Wang, W.; Wei, H.; Dang, L. MOF derived hollow CuO/ZnO nanocages for the efficient and rapid degradation of fluoroquinolones under natural sunlight. Chem. Eng. J. 2022, 436, 135119. [Google Scholar] [CrossRef] [Scilit]
  50. He, Q.; Song, Z.; Liu, L.; Xu, Y.; Huang, S.; Miao, Z. Ultrahigh-efficiency mineralization of butyl xanthate via peroxydisulfate activation by carbon cobalt composite catalyst. Fuel 2025, 386, 134263. [Google Scholar] [CrossRef] [Scilit]
  51. Nie, Q.; Liu, L.; Liu, J.; Shen, M.; Huang, X.; Tan, Z.; Yu, H. Photodegradation of xanthate using a Bi2Fe4O9/ZnIn2S4 heterojunction: Experimental and DFT Studies. Ind. Eng. Chem. Res. 2024, 63, 184–199. [Google Scholar] [CrossRef] [Scilit]
  52. Yang, Y.; Zhang, L.; Zhu, Y.; Wei, G.; Li, Z.; Mo, R. Three-dimensional photoelectrocatalytic degradation of ethyl xanthate catalyzed by activated bentonite-based bismuth ferrites particle electrodes: Influencing factors, kinetics, and mechanism. J. Environ. Chem. Eng. 2021, 9, 105559. [Google Scholar] [CrossRef] [Scilit]
  53. Yuan, J.; Ding, Z.; Gong, X.; Yu, A.; Wen, S.; Bai, S. Degradation of residual xanthate in flotation tailing wastewater by activated H2O2 with natural ilmenite: A heterogeneous fenton-like reaction catalyzed at natural pH. Sep. Purif. Technol. 2024, 332, 125819. [Google Scholar] [CrossRef] [Scilit]
  54. Feng, J.; Song, Z.; He, Q.; Wu, X.; Miao, Z. Enhanced degradation of butyl xanthate by hydrogen peroxide and persulfate using micro–nano bubble. Miner. Eng. 2024, 218, 108996. [Google Scholar] [CrossRef] [Scilit]
  55. Sheng, B.; Huang, X.; Zhao, Q.; Zhang, Z.; Duan, R.; Zhang, J.; Chen, C.; Zhao, J.; Sheng, H. Discriminative peroxymonosulfate activation on iron carbides for redox-neutral singlet oxygen generation. Angew. Chem. Int. Ed. 2025, 64, e202519774. [Google Scholar] [CrossRef] [Scilit]
  56. Li, Y.; Feng, Z.; Jia, H.; Zou, S.; Yang, T.; Li, M.; Huang, Y.; Zhao, H. Evolution of CoxNiy alloy electronic structure buffered by carbon nanolayer to tune selective generation of reactive oxygen species. Angew. Chem. Int. Ed. 2025, 64, e202512925. [Google Scholar] [CrossRef] [Scilit] [PubMed]
Catalysts 16 00460 g001
Figure 1. FSEM images and EDS mapping of (a) Fe-Zn-C and (b) Fe-C.
Figure 1. FSEM images and EDS mapping of (a) Fe-Zn-C and (b) Fe-C.
Catalysts 16 00460 g001
Catalysts 16 00460 g002
Figure 2. (a) XRD spectra, (b) Raman spectra (c) FTIR spectra, (d) N2 adsorption–desorption isotherms and (e) pore size distribution curves of Fe-Zn-C and Fe-C.
Figure 2. (a) XRD spectra, (b) Raman spectra (c) FTIR spectra, (d) N2 adsorption–desorption isotherms and (e) pore size distribution curves of Fe-Zn-C and Fe-C.
Catalysts 16 00460 g002
Catalysts 16 00460 g003
Figure 3. XPS spectra of (a) C 1s, (b) N 1s, (c) O 1s, (d) Fe 2p, (e) Zn 2p for Fe-Zn-C and Fe-C.
Figure 3. XPS spectra of (a) C 1s, (b) N 1s, (c) O 1s, (d) Fe 2p, (e) Zn 2p for Fe-Zn-C and Fe-C.
Catalysts 16 00460 g003
Catalysts 16 00460 g004
Figure 4. (a) UV absorbance spectra of BX, (b) BX (50 mg/L) degradation in Fe-Zn-C/PMS and Fe-C/PMS systems (Catalyst dose: 0.2 g/L, PMS concentration: 2 mM, temperature: 30 °C, initial pH: 7.0). Effect of (c) catalyst dosage (PMS concentration: 2 mM, temperature: 30 °C, initial pH: 7.0), (d) PMS concentration (Catalyst dose: 0.2 g/L, temperature: 30 °C, initial pH: 7.0), (e) initial pH (Catalyst dose: 0.2 g/L, PMS concentration: 2 mM, temperature: 30 °C), and (f) temperature (Catalyst dose: 0.2 g/L, PMS concentration: 2 mM, initial pH: 7.0).
Figure 4. (a) UV absorbance spectra of BX, (b) BX (50 mg/L) degradation in Fe-Zn-C/PMS and Fe-C/PMS systems (Catalyst dose: 0.2 g/L, PMS concentration: 2 mM, temperature: 30 °C, initial pH: 7.0). Effect of (c) catalyst dosage (PMS concentration: 2 mM, temperature: 30 °C, initial pH: 7.0), (d) PMS concentration (Catalyst dose: 0.2 g/L, temperature: 30 °C, initial pH: 7.0), (e) initial pH (Catalyst dose: 0.2 g/L, PMS concentration: 2 mM, temperature: 30 °C), and (f) temperature (Catalyst dose: 0.2 g/L, PMS concentration: 2 mM, initial pH: 7.0).
Catalysts 16 00460 g004
Catalysts 16 00460 g005
Figure 5. (a) Cycling experiment, (b) co-existing anions (Catalyst dose: 0.2 g/L, PMS concentration: 2 mM, initial pH: 7.0, temperature: 30 °C, anion concentration: 100 mM), (c) concentration of leaching Fe and Zn, (d) mineralization rate of BX during the cycling experiment of Fe-Zn-C system.
Figure 5. (a) Cycling experiment, (b) co-existing anions (Catalyst dose: 0.2 g/L, PMS concentration: 2 mM, initial pH: 7.0, temperature: 30 °C, anion concentration: 100 mM), (c) concentration of leaching Fe and Zn, (d) mineralization rate of BX during the cycling experiment of Fe-Zn-C system.
Catalysts 16 00460 g005
Catalysts 16 00460 g006
Figure 6. BX degradation curves in (a) Fe-Zn-C/PMS and (b) Fe-C/PMS systems using different quenching agents ([BX] = 50 mg/L, [catalyst] = 0.2 g/L, [PMS] = 2 mM, [MeOH] = [TBA] = [FFA] =1 M, [p-BQ] = 10 mM. T = 30 °C, initial pH = 7) and different concentration of (c) MeOH, (d) TBA, (e) FFA, and (f) p-BQ.
Figure 6. BX degradation curves in (a) Fe-Zn-C/PMS and (b) Fe-C/PMS systems using different quenching agents ([BX] = 50 mg/L, [catalyst] = 0.2 g/L, [PMS] = 2 mM, [MeOH] = [TBA] = [FFA] =1 M, [p-BQ] = 10 mM. T = 30 °C, initial pH = 7) and different concentration of (c) MeOH, (d) TBA, (e) FFA, and (f) p-BQ.
Catalysts 16 00460 g006
Catalysts 16 00460 g007
Figure 7. ESR spectra of DMPOX with DMPO as trapping agent in (a) Fe-Zn-C/PMS and (c) Fe-C/PMS systems, and 1O2 with TEMP as trapping agent in (b) Fe-Zn-C/PMS and (d) Fe-C/PMS systems.
Figure 7. ESR spectra of DMPOX with DMPO as trapping agent in (a) Fe-Zn-C/PMS and (c) Fe-C/PMS systems, and 1O2 with TEMP as trapping agent in (b) Fe-Zn-C/PMS and (d) Fe-C/PMS systems.
Catalysts 16 00460 g007
Catalysts 16 00460 g008
Figure 8. Mechanism diagram of BX degradation in Fe-Zn-C catalytic oxidation process.
Figure 8. Mechanism diagram of BX degradation in Fe-Zn-C catalytic oxidation process.
Catalysts 16 00460 g008
Table 1. BX degradation by different catalysts in previous studies.
Table 1. BX degradation by different catalysts in previous studies.
CatalystsDegradation RateTime (min)OxidationBX
Concentration (mg/L)
Co@C800-1 [50]97.7%60PDS (1 mM)100 mg/L
Bi2Fe4O9/ZnIn2S4 [51]98.25120Light20 mg/L
BiFe/Bent [52]97.85%150Na2SO4 (0.1 M)50 mg/L
FeTiO3 [53]98%100H2O2 (1 mM)40 mg/L
MNB/Fe2+ [54]68.59%90PMS (0.15 mM)100 mg/L
Fe-Zn-C (This study)96.54%30PMS (2 mM)50 mg/L
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Huang, S.; Xu, Y.; Jing, F.; Wang, L.; Sheng, J.; He, Q. Tunable Zn-Doping Enhanced Fenton-like Reaction for Butyl Xanthate Degradation: Unveiling the Non-Radical Reaction Pathway. Catalysts 2026, 16, 460. https://doi.org/10.3390/catal16050460

AMA Style

Huang S, Xu Y, Jing F, Wang L, Sheng J, He Q. Tunable Zn-Doping Enhanced Fenton-like Reaction for Butyl Xanthate Degradation: Unveiling the Non-Radical Reaction Pathway. Catalysts. 2026; 16(5):460. https://doi.org/10.3390/catal16050460

Chicago/Turabian Style

Huang, Shaomeng, Yiqing Xu, Feijian Jing, Liping Wang, Jiawen Sheng, and Qiongqiong He. 2026. "Tunable Zn-Doping Enhanced Fenton-like Reaction for Butyl Xanthate Degradation: Unveiling the Non-Radical Reaction Pathway" Catalysts 16, no. 5: 460. https://doi.org/10.3390/catal16050460

APA Style

Huang, S., Xu, Y., Jing, F., Wang, L., Sheng, J., & He, Q. (2026). Tunable Zn-Doping Enhanced Fenton-like Reaction for Butyl Xanthate Degradation: Unveiling the Non-Radical Reaction Pathway. Catalysts, 16(5), 460. https://doi.org/10.3390/catal16050460

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop