Nonradical Oxidation Pathway Research Articles

Oxygen vacancies-driven nonradical oxidation pathway of catalytic ozonation for efficient water decontamination

Developing catalysts with high efficiency and excellent interference tolerance for practical application remains a challenge in catalytic ozonation process. Herein, the surface Vo-rich catalyst was successfully prepared by lattice-doping Co into zinc ferrite spinel, which exhibited efficient mineralization of recalcitrant organic pollutants. The contaminants removal was mainly attributed to the nonradical-based oxygen species of surface atomic oxygen (*O) rather than traditional hydroxyl radical (·OH). The experiments and DFT calculation results revealed that Vo was the main active sites for adsorption of ozone and production of *O. The O-O in ozone was dissociated at Vo, trigging the formation of *O. In addition, the Vo-driven nonradical catalysis showed high resistance to the coexisting ions (200 mM Cl-, SO42- and NO3-) and exhibited excellent performance for actual wastewater treatment. This work provides a novel strategy to regulate the oxidation pathways in catalytic ozonation process for efficient mineralization of pollutants in complicated water matrices.

The role of heat/powdered activated carbon/persulfate in membrane fouling control in a coupled aerobic granular sludge–membrane system for municipal wastewater reclamation

This study proposed and applied an innovative heat/powdered activated carbon (PAC)/persulfate (PS) pre-treatment system for the first time in an aerobic granular sludge–membrane system (AGSMS). We examined the effects of the heat/PAC/PS system on membrane fouling mitigation and contaminant removal and qualitatively evaluated the contribution of adsorption and oxidation to membrane fouling control. Compared to other pre-treatment systems, the heat/PAC/PS system could enhance the removal of pollutants, reduce fouling resistance, and delay the decline of permeation flux, resulting in low foulant content on the membrane surface and formation of a loose and porous cake layer. According to radical scavenging experiments, the excellent heat/PAC/PS system pre-treatment performance was attributed to the PAC adsorption capacity and non-radical oxidation pathway. Thermal synergy played a significant role in promoting adsorption and oxidation abilities. The extended Derjaguin–Landau–Verwey–Overbeek theory indicated that the high-energy barrier in the heat/PAC/PS system was an important factor in inhibiting the adhesion of foulants to the membrane surface. Furthermore, the correlation analysis suggested that membrane fouling control should focus on the removal of chemical oxygen demand and suspended solids. This study provides a new approach for membrane fouling mitigation through AGSMS in municipal wastewater treatment.

Boosting singlet oxygen generation for salinity wastewater treatment through co-activation of oxygen and peroxymonosulfate in photoelectrochemical process

High concentrations of inorganic ions in saline wastewater pose adverse effects on hydroxyl radical (HO•)-dominated technologies. Here, we report a unique strategy for boosting singlet oxygen (1O2) generation via coactivation of oxygen and peroxymonosulfate (PMS) by regulating the electron transfer regime in the photoelectrochemical process. The Fe-N bridge in atomic Fe-modified graphitic carbon nitride (denoted SA-FeCN) favors the construction of electron-defective Fe and electron-rich N vacancies (Nvs) to accelerate directional electron transfer. The produced intermediate (HSO4O···Fe−Nvs···OO) as a chemical channel accelerates the directional electron transfer from PMS to further reduce O2 to form activated products (SO5•−, O2•−), thereby transforming O2 into 1O2. An optimized 1O2 generation rate of 39.4 μmol L−1s−1 is obtained, which is 15.7–945.0 times higher than that in traditional advanced oxidation processes. Fast kinetics are achieved for removing various phenolic pollutants in a nonradical oxidation pathway, which is less susceptible to the coexistence of natural organic matter and inorganic ions. The COD removal for coal wastewater and complex industrial wastewater in real scenarios is found to reach a value of 90%-96% in 3 h. This work provides a new direction for boosting the 1O2 generation rate, especially for the selective degradation of target electron-rich contaminants in saline wastewater.

Removal of Gaseous Volatile Organic Compounds by a Multiwalled Carbon Nanotubes/Peroxymonosulfate Wet Scrubber.

In this study, a wet scrubber coupled with a persulfate-based advanced oxidation process [carbocatalysts/peroxymonosulfate (PMS)] was demonstrated to efficiently remove gaseous volatile organic compounds (VOCs). The removal efficiency of a representative VOC, styrene, was stable at above 98%, and an average mineralization rate was achieved at 76% during 2 h. The removal efficiency of the carbocatalysts/PMS wet scrubber for styrene was much higher than that of pure water, carbocatalysts/water, or PMS/water systems. Quenching experiments, electron spin resonance spectroscopy, in-situ Raman spectroscopy and density functional theory (DFT) calculations indicated that singlet oxygen (1O2) and oxidative complexes are the main reactive oxygen species and that both contributed to styrene removal. In particular, carbonyl groups (C═O) in the carbocatalyst were found to be the active sites for activating PMS during styrene oxidation. The role of 1O2 was discovered to be benzene ring breaking and a possible non-radical oxidation pathway of styrene was proposed based on time-of-flight mass spectroscopy which was further verified by DFT calculations. In particular, the electron transfer process of multi world carbon nanotubes-PMS* in styrene oxidation was further studied in-depth by experiments and DFT calculations. The unstable vinyl on styrene was simultaneously degraded by the oxidative complexes and 1O2 into benzene, and finally oxidized by 1O2 into H2O and CO2. This study provides an effective method for VOC removal and clearly illustrates the complete degradation mechanism of styrene in a nonradical PMS-based process by a wet scrubber.

Biochar-based asymmetric membrane for selective removal and oxidation of hydrophobic organic pollutants

Hydrophobic organic pollutants (HOCs) in the complex groundwater and soil pose serious technical challenges for sustainable remediation. Herein, an asymmetric membrane (PCAM), inspired by the plant cuticle, was comprised of a top polydimethylsiloxane layer being selectively penetrable to HOCs from complex solution with humic acid, followed by transfer and catalyst layers with biochar pyrolyzed by 300 °C (BC300) and 700 °C (BC700). The PCAM triggered the advanced oxidation of the coming pollutant. The graphitized biochar layer of the PCAM acted as catalysts that induced HOC removal through a non-radical oxidation pathway. Compared to one type biochar membrane, the sequential multi-biochar composite membrane had a faster removal efficiency. The greater uptake and transport performance of multi-biochar composite membrane could be due to the larger pore size and distribution properties of PCAM physicochemical properties and oxidative degradation of peroxymonosulfate. The developed PCAM technology benefits from selective adsorption and catalytic oxidation and has the potential to be applied in complex environmental restoration.

Defect modulation of MOF-derived ZnFe2O4/CNTs microcages for persulfate activation: Enhanced nonradical catalytic oxidation

• ZnFe 2 O 4 /CNTs-Ar catalysts can efficiently activate PS to degrade BPA in a wide pH range. • Defective and porous microcages exhibit 17.5 times higher activity than blank ZnFe 2 O 4 . • Defect modulation of CNTs facilitated the electron transfer for nonradical degradation. • Magnetic property ensured the convenient collection of catalysts by magnets. • We offer a new strategy to enhance nonradical oxidation through defect modulation. There has been growing interest in the combination of porous metal organic frameworks (MOFs)-derived architectures with conductive carbonaceous materials for the synergistically enhanced catalytic activity. Herein, we described a facile strategy to synthesize a highly efficient and recyclable heterogeneous catalyst through pyrolysis of MOFs as sacrificial templates. We found that creating defective sites in CNTs precursors exhibited significant impact on the charge transfer capability of composite microcages and the coordination environment of Fe centers. With the assistant of persulfate oxidants, ZnFe 2 O 4 /CNTs-Ar with modulated defects exhibited 17.5-fold higher kinetic reaction rate (0.35 min −1 ) than blank ZnFe 2 O 4 microcages for Bisphenol A degradation. Experimental characterizations suggested that defective CNTs played a vital role in shuttling electron from BPA molecules to persulfate, triggered the direct decomposition of pollutants via a non-radical oxidation pathway. Our research provides a new strategy to develop high-performance MOFs-derived catalysts through defect modulation for wastewater treatment.

Highly dispersed and stable Fe species supported on active carbon for enhanced degradation of rhodamine B through peroxymonosulfate activation: Mechanism analysis, response surface modeling and kinetic study

Herein, highly dispersed Fe species supported on activated carbon (CA-Fe-C) was fabricated with the aid of citric acid, showing excellent catalytic performance and stability for the degradation of rhodamine B (RhB) through peroxymonosulfate (PMS) activation. The radical quenching study, electron paramagnetic resonance (EPR) measurement and PMS consumption analysis confirmed the RhB degradation mechanism involving reactive radical species attacking RhB and non-radical oxidation pathway. The main degradation intermediates were identified by LC-MS, and the possible RhB degradation pathways were deduced. A multivariate quadratic polynomial model was developed using the response surface methodology (RSM) to examine how the removal of RhB was influenced by several quantifiable factors, with the objective of optimizing RhB removal. The analysis of variance (ANOVA) was used to evaluate the adequacy and significance of the proposed model. The effects of solution pH values, initial concentration, inorganic anions, PMS dosage, catalyst dosage, and metal loading amount on RhB removal were investigated. The method of initial rates was employed to determine the intrinsic reaction rate law, and the reaction was identified to follow the Langmuir-Hinshelwood (L-H) kinetics model.

Rapid electron transfer boosts CuO-Mediated nonradical oxidation pathways for efficient removal of Bisphenol A

CO2 emission reduction and CO2 capture during wastewater treatment are the main objectives of carbon neutral wastewater treatment. Here, we show that CuO is expected to promote non-radical oxidation pathways through enhanced electron transfer. Calcination temperature may affect crystal growth and microscopic strain, and the smaller particle size of CuO provides shorter distance nanochannels for core-shell diffusion of electrons/defects. This facilitates fast electron transfer and easy in/out diffusion of electrons/defects, thus promotes 1O2-mediated nonradical oxidation (13.6-fold increase in kinetic reaction rate). A kinetic model was developed to predict the kinetic reaction rate constants of CuO/peroxymonosulfate (PMS) under different parameter conditions. The degradation pathways and product toxicity of pollutants are explored through Frontier Molecular Orbital Theory (FMO) and the Toxicity Estimation Software Tool (TEST). Due to the alkaline environment and the mild oxidation capacity of 1O2-mediated nonradical oxidation pathway, CuO/PMS system can not only effectively detoxify toxic organic pollutants without complete mineralization (emitting large amounts of CO2), but also capture CO2 and convert it into stable carbonates for environmental use. This study demonstrates the ability of CuO/PMS to effectively treat toxic organic pollutants in a practical microreactor, and provides a viable pathway for carbon neutral wastewater treatment.

Degradation of tetracycline hydrochloride through efficient peroxymonosulfate activation by B, N co-doped porous carbon materials derived from metal-organic frameworks: Nonradical pathway mechanism

• B, N co-doped carbon porous material was derived from metal-organic frameworks. • B-NC shows excellent performance in PMS activation and TC removal. • Singlet oxygen ( 1 O 2 ) was the domain active species in B-NC/PMS system. • Electron transfer was another non-radical oxidation pathway of B-NC/PMS system. • B-NC catalyst has relatively good stability for PMS activation. Peroxymonosulfate (PMS) based advanced oxidation process has been proved to be an efficient method for Antibiotic treatment. B, N co-doped carbon porous material was derived from metal-organic frameworks. B-NC catalysts showed excellent efficiency for removal of tetracycline hydrochloride. Nitrogen doping essentially changed the degradation pathway of tetracycline hydrochloride, while boron doping provided more active sites. through more defect sites, which is closely related to the adsorption and catalytic performance of the catalyst. The major active species of B-NC/PMS system was singlet oxygen ( 1 O 2 ) through quenching experiments and electron paramagnetic resonance (EPR) studies. Electron transfer was another non-radical oxidation pathway of B-NC/PMS system. This provides a new idea for the selective oxidation of antibiotics by metal-free activated PMS.

High microwave responsivity Co–Bi25FeO40 in synergistic activation of peroxydisulfate for high efficiency pollutants degradation and disinfection: Mechanism of enhanced electron transfer

Cobalt doped Bi25FeO40 was used as a heterogeneous catalyst in microwave (MW) co-activation of peroxydisulfate (PDS) system for organic contaminant purification and disinfection simultaneously. Due to low charge-transfer resistance and fast electron migration, Co–Bi25FeO40 showed superior catalytic efficiencies for activation PDS to degrade over 92.0% of bisphenol A (BPA) with the initial concentrations ranging from 40 mg/L to 120 mg/L in 5.0 min. The non-radical oxidation pathway via electron transfer regime on the surface of Co–Bi25FeO40 was the dominant reactive species in the reaction system. Benefit from the energy transfer and cross-coupling reactions of microwave, the Co–Bi25FeO40/MW/PDS system can generate abundant reactive sites to facilitate the formation of more surface-bonding complexes. Microwave energy can be absorbed by Co–Bi25FeO40 catalysts to promote activation of PDS and production of nanobubbles. The generated nanobubbles increase the temperature of the local solution to promote the reaction. The Co–Bi25FeO40/MW/PDS system also exhibited excellent bactericidal capability for Escherichia coli (E.coli). The catalysts, oxidants and microwaves acted on E. coli to form physical, and oxidative pressure simultaneously, causing cell damaged and made bacterial death. This work provides prospects toward high-efficiency integration of contaminant purification and pathogenic microorganisms inactivation.

Integration of heterogeneous photocatalysis and persulfate based oxidation using TiO2-reduced graphene oxide for water decontamination and disinfection

Advanced oxidation processes (AOPs) which involve the generation of highly reactive free radicals have been considered as a promising technology for the decontamination of water from chemical and bacterial pollutants. In this study, integration of two major AOPs viz., heterogeneous photocatalysis involving TiO2-reduced graphene oxide (T-RGO) nanocomposite and activated persulfate (PS) based oxidation was attempted to remove diclofenac (DCF), a frequently detected pharmaceutical contaminant in water. The enhanced visible light responsiveness of T-RGO would facilitate the use of direct sunlight as a benign and cost effective source of energy for the photocatalytic activation. By combining PS based oxidation process with T-RGO mediated photocatalysis, a DCF removal efficiency of more than 98% was achieved within 30 min. The effect of operating parameters like PS concentration and pH on DCF removal was assessed. Radical scavenging experiments indicated that apart from radical oxidation involving •OH and SO4·− radicals, a non-radical oxidation pathway was also taking place in the degradation. The antibacterial properties of the integrated system were also evaluated using Escherichia coli and Staphylococcus aureus as representative bacteria. The presence of PS in the photocatalytic reaction system improved the antibacterial activity of the composite against the two strains studied. Cytotoxicity of T-RGO nanocomposite was assessed using human macrophage cell lines and the results showed that the composite is biocompatible and nontoxic at the recommended dosage for water treatment in the present study.

Singlet oxygen-dominated activation of peroxymonosulfate by passion fruit shell derived biochar for catalytic degradation of tetracycline through a non-radical oxidation pathway

Waste-derived biochar has been emerged as promising catalysts to activate peroxymonosulfate (PMS) for the degradation of organic contaminants. Herein, passion fruit shell derived biochar (PFSC) was prepared by a one-pot pyrolysis method and used as a metal-free catalyst to activate PMS for the degradation of tetracycline hydrochloride (TC). The batch experiments indicated that the pyrolysis temperature could influence the efficiency of PFSC for the activation of PMS. In the PFSC-900 (prepared at 900 °C)/PMS system, the degradation rate of TC can reach 90.91%. The quenching test and electron paramagnetic resonance spectra revealed that the high catalytic performance of PFSC-900/PMS system was mainly attributed to the non-free radical reaction pathway containing a carbon bridge, and the TC degradation was controlled primarily by singlet oxygen-mediated oxidation. Moreover, the carboxyl group of ketones and the graphite-N atoms on PFSC-900 are the possible active sites of the non-free radical pathway including direct electron transfer or the formation of O2•-/1O2. This study not only shows a new type of biochar as an efficient catalyst for PMS activation but also provides a way of value-added reuse of passion fruit shell.

Insight into the difference in activation of peroxymonosulfate with nitrogen-doped and non-doped carbon catalysts to degrade bisphenol A

Heteroatom-modified carbon-based catalysts (especially nitrogen-doped) have been reported to be effective in activating peroxymonosulfate (PMS). Nevertheless, here our study found that graphitized carbon nanomaterial (GC800) exhibited a similar catalytic capacity as the nitrogen-doped graphitized carbon nanomaterial (NGC800) in the degradation of bisphenol A (BPA) via activating PMS, however, the degradation rate constant of the former was approximately 1.72-times greater than that of the latter. Meanwhile, GC800 showed admirable versatility, wide application range of pH value and excellent stability. Furthermore, the connection between the difference in surface chemistry (surface functional groups, electronic properties) and reaction rate between GC800 and NGC800 was discussed. Quenching experiments combined with electron paramagnetic resonance (EPR) and electrochemical measurements revealed the existence of a multi-pathway synergy in GC800/PMS system dominated by the non-radical electron-transfer pathway and complemented by radical (O2•−)/non-radical (1O2) pathway. The high proportion of carbonyl groups and sp2-hybridized carbon as the main parameters affected the electron density of GC800 in the process of non-radical electron transfer. In contrast, NGC800/PMS system only followed the non-radical oxidation pathway with singlet oxygen being the predominant ROS. Pyrrolic N affected the non-radical oxidation pathway of NGC800. This work verifies the significant role of surface chemistry of carbon materials and the synergy between non-radical electron transfer and radical/non-radical oxidation on the catalytic velocity. And it presents a novel thought in the design of high-efficiency carbon-based catalysts toward green and sustainable ecological restoration.

Incorporating Fe3C into B, N co-doped CNTs: Non-radical-dominated peroxymonosulfate catalytic activation mechanism

Boron and Nitrogen co-doped carbon nanotubes incorporated iron carbide (Fe3C) nanoparticles (Fe3C@BN-C) were successfully prepared by one-step pyrolysis method employing melamine, ferric chloride and boric acid as precursors. Characterizations indicate that the catalyst has large specific surface area (258.17–305.74 m2/g) and abundant defect sites, which are closely related to the adsorption performance and catalytic efficiency of the catalysts. In the presence of peroxymonosulfate (PMS), the removal rates of Fe3C@BN-C-7, Fe3C@BN-C-8 and Fe3C@BN-C-9 for doxycycline hydrochloride (DOX-H) are 87.0%, 91.9% and 86.0% within 120 min. Fe3C nanoparticles, oxygen-containing functional groups, pyridinic N, pyrrolic N, graphite N and B, N dopants play a vital role in the improvement of catalytic activity. Quenching experiments and electron paramagnetic resonance (EPR) studies show that singlet oxygen (1O2) is dominant reactive oxygen species, demonstrating that the degradation reaction predominantly follows the non-radical oxidation pathway. The possible degradation pathway of DOX-H is proposed and 14 intermediate products are reported for the first time. This work not only provides a novel and valuable catalyst for pharmaceutical wastewater treatment, but also reveals a new perspective for the study of activated PMS dominated by non-radical pathway.

Insight into the effect of lignocellulosic biomass source on the performance of biochar as persulfate activator for aqueous organic pollutants remediation: Epicarp and mesocarp of citrus peels as examples

In this work, the cellulose-enriched mesocarp of tangerine peels (TP) and the lignin-enriched epicarp of the peels (e-TPs) were used as examples to unveil the link between the basic components (cellulose, hemicellulose and lignin) in lignocellulosic biomass and catalytic activity of biochar towards peroxymonosulfate (PMS) activation. The TP biochar exhibits sheet-like morphology and high porosity, while the e-TPs biochar shows a bulk morphology. Accordingly, the former outperformed the latter in terms of catalytic degradation of phenol with PMS, attributing to the higher content of cellulose than lignin in the TP precursor, which was further supported by comparing the catalytic activity of biochar prepared from binary mixtures containing different proportions of cellulose and lignin. Nonradical oxidation pathway based on singlet oxygen (1O2) and electron-transfer mechanism was involved in the TP biochar/PMS system and the key role of CO group in biochar for 1O2 generation was computationally demonstrated. Additionally, the unique porous structure and surface chemistry of TP biochar endows it an excellent adsorbent for various organic pollutants. Herein, this work provides an insight into the effect of lignocellulosic biomass source on the catalytic property of biochar, which would be beneficial to screen lignocellulosic biowastes to prepare high-performance biochar for water remediation.

A unique Si-doped carbon nanocatalyst for peroxymonosulfate (PMS) activation: insights into the singlet oxygen generation mechanism and the abnormal salt effect

The Si-engaged, carbon-activated peroxymonosulfate (PMS) system proceeding via the non-radical oxidation pathway involving singlet oxygen (1O2) represents a promising advanced oxidation process.

Oxidative degradation of pharmaceutical losartan potassium with N-doped hierarchical porous carbon and peroxymonosulfate

Losartan potassium (LOS) is a most globally consumed antihypertensive and emerging pharmaceutical contaminant of concern due to increasingly ubiquity in water and wastewater. For its effective environmental remediation, we propose the catalytic oxidation of losartan via peroxymonosulfate (PMS) activation using a metal-free N-doped hierarchically porous carbon (N-PC). We found out that N-PC exhibits both excellent adsorption capacity and catalytic oxidation efficiency with 100% LOS uptake within 240 min at 0.026 g/L of the N-PC. Fresh and used N-PC were scrutinized for textural properties and surface chemistry. The effects of PMS dose, temperature, pH, organic matter and coexisting anions on losartan decomposition were examined. Moreover, total organic removal was obtained and the catalyst was tested in three consecutive runs. Electron paramagnetic resonance and quenching assays revealed that the nonradical oxidation pathway plays a major role in LOS degradation by N-PC/PMS.

High-performance porous graphene from synergetic nitrogen doping and physical activation for advanced nonradical oxidation

Porous nitrogen-doped reduced graphene oxide (NRGO) is successfully synthesized from graphene oxide via the combination of CO2 activation and nitrogen doping with ammonia. The performances of the carbon materials are evaluated by catalytic activation of perroxymonosulfate (PMS) for phenol degradation. The effect of the treatment sequence of CO2 activation and nitrogen doping on the catalytic activity of the derived product is investigated. The material obtained by CO2 activation-nitrogen doping (P-NRGO) shows better activity than the one obtained from nitrogen doping-CO2 activation (N-PRGO). The activation mechanisms are also investigated by radical scavenging test, and the P-NRGO/PMS system is unveiled to rely on the nonradical oxidation pathway. The turnover frequencies (TOFs) of these RGOs are also calculated, and the P-NRGO has the largest TOF of 58.39. Based on the analysis of synthesis method and catalytic activity, it is proposed that new catalytic sites are generated on P-NRGO. Density functional theory (DFT) calculations also illustrated that the most reactive sites are the structure vacancies with two nitrogen atoms, which is consistent with the results. The conclusion in this study provides new insights into the synergistic effect of N-doping and structural defects of carbon materials and the induced nonradical pathway in advanced oxidation.

Singlet oxygen dominated peroxymonosulfate activation by CuO-CeO2 for organic pollutants degradation: Performance and mechanism

In this study, CuO-CeO2 was synthesized via an easy hydrothermal-calcination method and innovatively applied to peroxymonosulfate (PMS) activation for pollutants degradation under a non-radical oxidation pathway. Singlet oxygen (1O2) was the dominated reactive oxygen species in the CuO-CeO2/PMS system, leading to a dramatical degradation efficiency with Rhodamine B (RhB) as model compounds. The observed rate constant of the CuO-CeO2/PMS system was 7–11 times higher than that of only PMS, CeO2/PMS and CuO/PMS systems. Also, under the reaction conditions of 1.6 mM PMS, 0.4 g/L catalyst and initial pH 7, the degradation efficiencies of RhB, Methylene Blue, Reactive Blue 19 and atrazine were respectively up to 100%, 85.39%, 72.84% and 98.44% in 60 min. X-ray photoelectron microscopy analysis indicated that the electrons transfer between CuO and CeO2 and the formation of oxygen vacancy in CeO2 should be responsible for the enhanced 1O2 production, which involved a new non-radical oxidation pathway for PMS activation by CuO-CeO2 catalyst. Moreover, the combination of CuO and CeO2 increased reusability and stability of catalyst, allowing it remove more than 92% of RhB over a wide pH range (pH = 3–9). This study not only proved that CuO-CeO2 is an efficient and stable PMS activator but also provided a new insight into PMS activation through a non-radical oxidation pathway for organic contaminants removal from wastewater.

Nitrogen-sulfur co-doped industrial graphene as an efficient peroxymonosulfate activator: Singlet oxygen-dominated catalytic degradation of organic contaminants

This paper presents for the first time the doping of nitrogen (N) and sulfur (S) into industrial reduced graphene oxide (i-rGO) to synthesize the catalyst, named as i-rGO-NS, to activate peroxymonosulfate (PMS). Co-doping of N and S into the catalyst was investigated by many surface techniques. The i-rGO-NS catalyst had the higher content of graphitic N (˜34%) than only N-doped rGO (i.e., i-rGO-N). The i-rGO-NS showed high activation of PMS for catalyzing oxidation of target contaminant, methyl paraben (MP), an endocrine disruptor in water under various conditions (reaction temperature, catalyst loading and PMS dosage). In comparison with the conventional GO and its N-doped or N/S-co-doped composites and classical metal catalysts (e.g., Co3O4 and Fe3O4), i-rGO-NS has superior effectiveness to activate PMS to degrade contaminants even under the conditions of less dosage of the catalyst (i-rGO-NS) and oxidant (PMS). Results suggest that the N doping, and especially additional S doping were of pivotal in enhancing catalytic performance. Transformation pathways of MP in the i-rGO-NS/PMS system were tentatively proposed that agree with the identified intermediates and frontier electron density calculations. Quenching tests and electron paramagnetic resonance (EPR) studies showed that the singlet oxygen (1O2) was the main reactive oxygen species, revealing that MP degradation follows predominantly the nonradical oxidation pathway. The i-rGO-NS/PMS system not only exhibited considerable removal efficiency of MP in real waters, but also showed the rapid degradation of other pollutants (e.g., UV filter benzophenone-4 (BP-4) and phenol) in water. The newly developed nonradical i-rGO-NS/PMS process is highly effective in decontamination of water.