Persulfate Activation Mechanism Research Articles

Unveiling activation mechanism of persulfate by homologous hemp-derived biochar catalysts for enhanced tetracycline wastewater remediation

Advancements in biochar activating persulfate advanced oxidation processes (PS-AOP), have gained significant attention. However, the understanding of biochar-based catalysts in activating PS remains limited. Herein, biochar (BC) and N-doped biochar (NBC) were synthesized from hemp for activating PS to treat tetracycline (TC) wastewater and analyzed their mechanisms separately. Surprisingly, N-doped in biochar leads to a change in the activation mechanism of PS. The BC-PS system operates mainly through a radical pathway, advantageous for treating soil organic pollution (68%) with pH adaptability (less than 10% variation). Nevertheless, the NBC-PS system primarily employs an electron transfer non-radical pathway, demonstrating stability (only 7% performance degradation over four cycles) and enhanced resistance to anionic interference (less than 10% variation) in organic wastewater treatment. This study provides a technical reference and theoretical foundation for enhancing biochar activation of PS in the removal of organic pollutants from aquatic and terrestrial environments.

Magnetic nickel ferrite for efficient persulfate activation to remove aqueous refractory organics: Synthesis, advantages, mechanism, and environmental implications

Magnetic spinel ferrites are promising catalysts for activating persulfate for aqueous organics removal. Herein, a high-efficiency ferrite NiFe2O4 was synthesized and comprehensively investigated for persulfate activation. The optimal preparation conditions and their interactions were successfully determined by response surface methodology. The resultant catalyst was characterized with favorable properties for persulfate activation, e.g., porous morphology, excellent magnetism, and good redox activity. The study of operating parameters showed good adaptability of the NiFe2O4 +PS system to pH variation (3–9), and 100 % diclofenac removal was achieved. Mineralization and PS consumption tests showed high TOC removal (65.6 %) and a low PS demand (PS:diclofenac = 6.7:1), which were clear advantages of NiFe2O4, indicating its excellent activity towards PS decomposition. Additionally, the catalyst could be recovered quickly and completely during reuse (> 90 % recovery within 10 s). In addition, persulfate was considered to bind to the catalyst via electrostatic and chemical bonding, followed by the generation of surface-bound SO4•−. A potential mechanism of persulfate activation by NiFe2O4 and three possible degradation routes of diclofenac were proposed. Finally, the environmental implications of the NiFe2O4 +persulfate system for treating actual waters and multiple pollutants were revealed. This work supplemented ferrite for persulfate activation and provided an effective oxidative system for decontamination.

Insights into the mechanism of persulfate activation by hollow MOF-derived carbon: electron transfer-triggered non-radical oxidization for antibiotic removal

Hollow ZIF-8-derived carbon is fabricated via TA etching and carbonization. Graphitic N plays a vital role in electron transfer non-radical oxidization. The hollow structure induces the evolution from an ROS-driven to an electron-transfer process.

Efficient recovery of iron from anaerobic roasted cyanide tailings using advanced oxidation technology

Persulfate-mediated advanced oxidation process (AOP) has been used to oxidize iron and sulfur bearing minerals, but the iron leaching process and the activation of persulfate by minerals themselves has been neglected. In this study, AOP was used to leach iron from cyanide tailings, roasted in a nitrogen atmosphere. The oxidation behavior of pyrrhotite and the activation mechanism of persulfate were proposed through process optimization, product analysis, reactive species and degradation area. The iron leaching efficiency from roasted cyanide tailings was 97.1%, with a mass loss ratio of 32.5%. The gold grade in leach residues increased from 1.19 g/t to 2.07 g/t under the leaching conditions: sodium persulfate concentration of 0.3 mol/L, leaching temperature of 60 °C, slurry concentration of 30 g/L, and stirring speed of 300 rpm. The pyrrhotite in roasted cyanide tailings was oxidized by persulfate and the free radicals produced by its activation. Oxidation products were Fe3+, SO42−, and elemental sulfur. The oxidation of pyrrhotite was dominated by the indirect oxidation by the free radicals OH• and SO4−•, and their contributions to the iron leaching efficiency were 66.6% and 24.2%, respectively. The reason for the thermally enhanced iron leaching effect was the activation of persulfate to produce a certain amount of OH•. The Fe2+ produced by the oxidation of pyrrhotite activated persulfate to produce SO4−• and OH•. Besides, S(II) in pyrrhotite mediated the circulation of iron ions, thereby continuously producing Fe2+ to activate persulfate.

Persulfate activation using leonardite char-supported nano zero-valent iron composites for styrene-contaminated soil and water remediation

Effective in-situ technology to treat carcinogenic compounds in contaminated areas poses a major challenge. Our objective was to load nano-zero-valent iron (nZVI) onto leonardite char (LNDC), an alternative carbon source from industrial waste, for use as a persulfate (PS) activator for styrene treatment in soil and water. By adding a surfactant during synthesis, cetyltrimethylammonium bromide (CTAB) promotes a flower-like morphology and the nZVI formation in smaller sizes. Results showed that nZVI plays a crucial role in PS activation in both homogeneous and heterogeneous reactions to generate reactive oxygen species (ROS), which can remove 98% of styrene within 20 min. Quenching experiments indicated that singlet oxygen (1O2), superoxide radicals (O2•–), and sulfate radicals (SO4•–) were the main species working together to degrade styrene. XPS analysis also revealed a role of surface oxygen-containing groups (i.e., CO, C–OH) in activating PS for SO4•– and 1O2 generation. The possible reaction mechanism of PS activation by LNDC-CTAB-nZVI composite and factors affecting treatment efficiency (i.e., PS concentration, catalyst dosage, pH, and humic acid) were illustrated. The molarity/molality ratio of PS to nZVI should be set greater than 1 for effective styrene removal. GC-MS analysis showed that styrene was degraded to a less toxic benzaldehyde intermediate. However, the excessive use of PS and catalysts can harm plant growth, requiring a combining approach to achieve safer use for real applications. Overall results supported the use of the LNDC-CTAB-nZVI/PS system as an efficient in-situ treatment technology for soil and water remediation.

Mechanism insights into photo–assisted peroxymonosulfate activation on oxygen vacancy–enriched nolanites via an electron transfer regime

The utilization of photo–assisted persulfate activation for the removal of organic contaminants in water has garnered significant research interest in recent times. However, there remains a lack of clarity regarding specific contributions of light irradiation and catalyst structure in this process. Herein, a photo–assisted peroxymonosulfate (PMS) activation system is designed for the highly efficient degradation of organic contaminants on oxygen vacancy–enriched nolanites (Vo–FVO). Results suggest that the degradation of bisphenol A (BPA) in this system is a nonradical–dominated process via an electron transfer regime, in which VO improves the local electron density and thus facilitates the electron shuttling between BPA and PMS. During BPA degradation, PMS adsorbed at the surface of FVO–180 withdraws electrons near VO and forms FVO–PMS* complexes. Upon light irradiation, photoelectrons effectively restore the electron density around VO, thereby enabling a sustainable electron transfer for the highly efficient degradation of BPA. Overall, this work provides new insights into the mechanism of persulfate activation based on defects engineering in nolanite minerals.

Electrodeposited copper enhanced removal of 2,4-dichlorophenol in batch and flow reaction in Cu@CC-PS-MFC system

Combination of microbial fuel cell (MFC) and advanced oxidation process (AOP) is promising for pollutant removal. In this paper, Cu0-loaded carbon cloth cathode by electrodeposition (Cu@CC-PS-MFC) was applied to enhance 2,4-dichlorophenol (2,4-DCP) degradation based on persulfate (PS) activation in microbial fuel cell. Cu0 exhibited a typical structure of face-centered cubic metal polyhedron on carbon cloth. The removal of 2,4-DCP by Cu@CC-PS-MFC (75.6%) was enhanced by more than 50% compared to CC-PS-MFC (49.2%) after 1 h of reaction. 30 mg/L 2,4-DCP in Cu@CC-PS-MFC was completely removed and achieved a high mineralization (80.6%) after 9 h of reaction under optimized condition with low dissolved copper ion concentration (0.615 mg/L). Meanwhile, more than 90% removal of 2,4-DCP was stably achieved with flow operation condition (hydraulic residence time of 7.2 h). The change of copper valent state Cu0/Cu2O/CuO was the main mechanism of PS activation with main reactive species of O•H and O21. The bioanode of MFC enhanced the in-situ regeneration of ≡Cu+ and ≡Cu0 on the catalyst surface by transporting electrons, which was believed to contribute to good catalyst lifetime and excellent 2,4-DCP removal. Electrodeposited copper contributes to the enhanced degradation of 2,4-DCP with energy recovery at the same time which can further broaden the application MFC.

Rapid degradation of organic pollutants by enhanced persulfate activation using CeO2-MnFe2O4 nanostructures: A polymetallic synergistic effect

Persulfate-based advanced oxidation processes (AOPs) have attracted considerable attention in the treatment of organic wastewater with high performance and long lifetime. The construction of efficient, environmentally-friend, and stable nanocatalysts has been recognized as a promising approach to activate persulfate. Herein, magnetic CeO2-MnFe2O4 nanomaterials fabricated via a simple sol-gel method were used for the first time to enhanced activate persulfate (PS) for the removal of the organic pollutant enrofloxacin (ENR). It was demonstrated that 97.2% of ENR (10 mg L−1) was efficiently degraded. 63.3% of TOC decreased within 35 min under a neutral solution (pH 6.81) in the PS+CeO2-0.2MnFe2O4 system using a catalyst dosage of 0.25 g L−1 and 0.18 mM PS. The magnetic CeO2-MnFe2O4 nanostructures maintained excellent recovery as well as recyclability ENR removal efficiency was 90% after recycling five times. EPR and quenching tests indicated that sulfate radicals (SO4•−) and hydroxyl radicals (•OH) significantly contributed to ENR removal. XPS analysis showed that the synergistic redox cycles of Ce3+/Ce4+, Mn2+/Mn3+, and Fe2+/Fe3+ are essential to activate PS for ENR degradation. DFT calculations also revealed that PS molecules preferred to adsorb to and dissociate on CeO2-MnFe2O4 surfaces rather than just CeO2 and MnFe2O4 surfaces. CeO2 plays a dual role in the charge transfer from CeO2-MnFe2O4 to PS molecules, i.e., both electron storage and donor. This work also provides a new interpretation to explain the activation mechanism of PS. The developed CeO2-MnFe2O4 nanostructures with rapid removal efficiency, high degradation efficiency and good recyclability may provide potential guidance for the design of polymetallic oxide nanocatalysts in PS-based AOPs.

In-situ synthesis of magnetic iron-chitosan-derived biochar as an efficient persulfate activator for phenol degradation

Persulfate activation is a forceful method for eliminating organic pollutants from coal chemical wastewater. In this study, an in-situ synthesis method was used to fabricate an iron-chitosan-derived biochar (Fe-CS@BC) nanocomposite catalyst using chitosan as a template. Fe was successfully imprinted into the newly synthesized catalyst. The Fe-CS@BC can activate persulfate to effectively degrade phenol. This point was confirmed by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The impact of various parameters on the removal rate was investigated in a single factor experiment. In Fe-CS@BC/PDS system, 95.96% of phenol (significantly higher than the original biochar of 34.33%) was removed within 45 min and 54.39% TOC within 2 h. The system showed superior efficiency over a broad pH value band from 3 to 9 and has a high degradation rate at ambient temperature. Free radical quenching experiment, EPR experiment and LSV experiment confirmed that multiple free radicals (including 1O2, SO4•-, O2•- and •OH) and electron transfer pathway combined to enhance phenol decomposition. Finally, the activation mechanism of persulfate by Fe-CS@BC was proposed to provide logical guidance on the treatment of organic pollutants in coal chemical wastewater.

The performance and mechanism of persulfate activation boosted MoO2@LDHs Z-scheme heterojunction for efficient photocatalytic degradation of tetracycline

Photocatalytic activation of persulfate for the synergistic degradation of pollutants has become a major research hotspot, but the activation effect is poor due to the problems of low catalyst carrier separation efficiency and insufficient active sites. In this study, direct Z-Scheme heterojunctions of MoO2@CoFe LDHs were prepared by a simple hydrothermal method and a Co and Fe dual active site system was constructed to activate Na2S2O8 (PS) for the synergistic degradation of tetracycline under visible light. The results showed that the synergistic degradation of tetracycline was 3.7 times and 2.7 times more efficient than the original heterojunction and PS, respectively. Combining material characterisation, photovoltaic performance tests and theoretical calculations revealed that the high efficiency is attributed to the formation of an internal electric field under the Z-Scheme heterostructure type generating effective electron-hole separation, with more photo-generated electrons converted into radicals acting together with holes to degrade the TC and activate the PS. More importantly, Co(II) and Fe(II) provide electrons to synergistically activate PS, and a portion of the photogenerated electrons and PS activation intermediates can facilitate cycling between Co(II)/Co(III) and Fe(II)/Fe(III) to accelerate PS activation. This paper's work on activating PS-assisted Z-Scheme heterojunctions for the efficient degradation of TC provides a reference for the study of high-performance photocatalytic catalysts for the degradation of organic pollutants.

Synergy between MgFe2O4 and biochar derived from banana pseudo-stem promotes persulfate activation for efficient tetracycline degradation

Exploiting environment-friendly and cost-effective catalysts and understanding their catalytic mechanisms are a great challenge in persulfate-based advanced oxidation processes (PS–AOPs). Herein, a simple sol–gel pyrolysis procedure was employed to generate a novel magnesium ferrite/biochar (MgFe2O4/BC), exhibiting excellent degradation abilities to tetracycline (TC) (94.70% within 90 min). Characterization results demonstrated that biochar (BC) increased the dispersibility, surface area, and electronic transfer capability of MgFe2O4. Compared with the single MgFe2O4 and BC, the TC degradation efficiency of the novel MgFe2O4/BC was significantly improved by 78.49% and 45.97%, which ascribed to the synergies causing the composite possessed large specific surface area and exposing more active sites. The quenching test and electron spin resonance revealed the dominance of 1O2 and O2•− among the identified reactive oxygen species. Oxygen vacancy and carbonyl were identified as the main active sites. A possible TC degradation pathway has been proposed, and reduced toxicity of intermediates was observed. This study provides a new perspective on understanding the persulfate activation mechanism by spinel-biochar composites.

Insight into the degradation of sulfamethoxazole in novel persulfate activation system based on steel slag-based geopolymer

Due to high redox potential and long half-life, the sulfate radical based advanced oxidation processes have attracted extensive attention in the treatment of environmental pollution. Persulfate can be activated by ultraviolet light, heat and iron based materials. Among the numerous iron-based activators, steel slag has gained considerable interest as a material containing iron fractions due to their cost-effective, broad variety of sources and their ability to realize solid waste recycling. In this study, a novel proposed steel slag-based geopolymer system was applied to remove sulfamethoxazole for the first time. Sulfamethoxazole was degraded by 90.84% within 60 min in the system. Both EPR and quenching studies indicated that both SO4•− and HO• were the primary reactive oxygen species for the degradation of sulfamethoxazole. As the source of iron, steel slag-based geopolymer provide Fe species in the forms of Fe(II) and Fe(Ⅲ). Investigation on the persulfate activation mechanism suggested that both surface Fe(II) and dissolved Fe2+ contribute to persulfate activation. The presence of surface Fe(II) play dominant role on persulfate activation. The findings of this study reveal that steel slag-based geopolymer can realize the recycling of solid waste and exhibit a good job on antibiotic removal.

Insights into the mechanism of persulfate activation with biochar composite loaded with Fe for 2,4-dinitrotoluene degradation

Iron in biochar composite loaded with Fe (Fex@biochar) is crucial for persulfate activation. However, the iron dosages-driven mechanism linked to the speciation, electrochemical property, and persulfate activation with Fex@biochar remains ambiguous. We synthesized and characterized a series of Fex@biochar and evaluated its catalytic performance in 2,4-dinitrotoluene removal experiments. With increasing FeCl3 dosage, iron speciation in Fex@biochar changed from γ-Fe2O3 to Fe3O4, and the variation in functional groups was as follows: Fe–O, aliphatic C–O–H, O–H, aliphatic C–H, aromatic CC or CO, and C–N. The electron accepting capacity of Fex@biochar increased as the FeCl3 dosage increased from 10 to 100 mM but decreased at 300 and 500 mM FeCl3. 2,4-dinitrotoluene removal first increased and subsequently decreased, reaching 100% in the persulfate/Fe100@biochar system. The Fe100@biochar also showed good stability and reusability for PS activation, verified by five test cycles. The mechanism analysis indicated that the iron dosage altered the Fe (Ⅲ) content and electron accepting capacity of Fex@biochar during pyrolysis, further controlling persulfate activation and 2,4-dinitrotoluene removal. These results support the preparation of eco-friendly Fex@biochar catalysts.

Heterogeneous activation of persulfate using delafossite AgFeO2/α-MnO2 for efficient degradation of tartrazine under visible light

For the first time, delafossite AgFeO2/α-MnO2 nanocomposites were successfully synthesized and used as heterogeneous persulfate (PS) activators for degradation of water pollutants. The potential of several systems, such as AgFeO2/α-MnO2/light, AgFeO2/α-MnO2/PS/light, etc., as well as reaction conditions, stability, and radicals involved, were all assessed for degradation of tartrazine (TZ). The exceptional activity of optimal AgFeO2/α-MnO2 (AFM50) nanocomposite was attained because of improved redox cycling between Ag0/Ag+, Fe2+/Fe3+, Mn3+/Mn4+ cycles, enhanced electron transfer, reduced e−/h+ pair recombination, long electron lifetime, high charge transfer and mobility, and electron density, which facilitated efficient PS activation and subsequent generation of various reactive oxidizing species. Interestingly, AFM50 showed exceptional degradation efficiency (67.4%) under dark conditions. The AFM50/PS/Vis system also demonstrated excellent stability and activity for degrading several dyes (rhodamine B (97.8%), methyl orange (94.5%), methylene blue (100%), and congo red (97.7%)). Based on quenching experiments, active radicals (•OH, SO4•-, O2•-), and non-radical (h+, 1O2), all contributed towards efficient degradation of TZ. Following that, a reasonable PS activation mechanism was proposed. This study propounds insightful synergistic activation of PS using delafossite AgFeO2/α-MnO2 nanocomposite under visible light and dark conditions, as well as its potential application in wastewater treatment plants.

Insights into the mechanism of persulfate activation with carbonated waste metal adsorbed resin for the degradation of 2,4-dichlorophenol

Superabsorbent resin (SAR) saturated with heavy metals poses a threat to surrounding ecosystem. To promote the reutilization of waste, resins adsorbed by Fe2+ and Cu2+ were carbonized and used as catalysts (Fe@C/Cu@C) to activate persulfate (PS) for 2,4-dichlorophenol (2,4-DCP) degradation. The heterogeneous catalytic reaction was mainly responsible for 2,4-DCP removal. The synergistic effect of Fe@C and Cu@C was propitious to 2,4-DCP degradation. Fe@C/Cu@C with a ratio of 2:1 showed the highest performance of 2,4-DCP removal. 40 mg/L 2,4-DCP was completely removed within 90 min under reaction conditions of 5 mM PS, pH = 7.0 and T = 25 °C. The cooperation of Fe@C and Cu@C facilitated the redox cycling of Fe and Cu species to supply accessible PS activation sites, enhancing ROS generation for 2,4-DCP degradation. Carbon skeleton enhanced 2,4-DCP removal via radical/nonradical oxidation pathways and via its adsorption to 2,4-DCP. SO4˙ˉ, HO˙ and O2•− were the dominate radical species involved in 2,4-DCP destruction. Meanwhile, the possible pathways of 2,4-DCP degradation were proposed based on GC-MS. Finally, recycling tests proved catalysts exhibited recyclable stability. Aiming to resource utilization, Fe@C/Cu@C with satisfactory catalysis and stability, is promising catalyst for contaminated water treatment.

Rational regulation of peroxymonosulfate activation over porous Co3O4 with carbon coating to boost utilization efficiency of peroxymonosulfate and achieve rapid removal of pollutants

It is of great significance to regulate rationally the activation mechanism of persulfate for promoting the development of sulfate radical-based advanced oxidation processes in wastewater treatment. Herein, carbon coated porous Co3O4 with hollow structure was synthesized. Notably, the formation of porous hollow structure improved specific surface area of Co3O4 and offered more redox couples of Co2+/Co3+, thereby reducing electron transfer resistance. Thus, the generation of reactive oxygen species and the role of high-valent transition metal complexes (namely Co3O4Co4+) were improved. The formation of carbon layer on the Co3O4 surface can avoid the release of Co ion during reaction process. Benefiting from the role of carbon layer in electron transport, catalyst-mediated the direct electron transfer from pollutant to PMS was boosted. Radical and nonradical pathways worked in coordination each other and realized the rapid removal of various organic pollutants in the presence of a little PMS. In short, current work revealed that modulating rationally the microstructure of catalyst was an efficient strategy for achieving controllable regulation of PMS activation process. More significantly, whether the direct electron transfer process can occur or not depended on both catalyst structure and electronic density of pollutants.

A magnetic sludge carbon combined persulfate-based ISCO system for leachate-contaminated groundwater remediation

Activation of persulfate by a green magnetic Steel Converter Slag-Sludge Carbon composite (SCS@SC) and subsequent remediation of actual leachate wastewater was studied in an intermittent reactor and column system to assess the potential of the persulfate-based in situ chemical oxidation (SR-ISCO) system for combined oxidative-reductive removal of organic contaminants from groundwater. In the batch experiment, an iron leaching concentration of 6942 mg/L, was higher than 223.2 and 124.4 times that of steel converter slag (31.14 mg/L) and sole sludge carbon (55.80 mg/L). In the column experiments, the total organic carbon (TOC) removal was maintained at 41.7 %, the loading rate reached 48.86 % with 15 g SCS@SC and 0.15 M persulfate after 400 min. The persulfate consumption, sulfuric acid generation, free radical generation, and iron ions flow out under acidic conditions, which are consistent with TOC removal. The mechanism of persulfate activation and organic matter removal was discussed and proposed by electron paramagnetic resonance (EPR) and energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and gas chromatography-mass Spectrometry (GC–MS) to characterize the chemistry of solid and aqueous phases. A mechanism for contaminant removal was presented, which involves free radicals of persulfate activation by zero-valent iron (Fe0) and iron carbide (Fe3C) and precipitation removal by iron oxides. According to the findings, a viable alternative method for the inexpensive synthesis of catalysts from solid wastes such as sludge and steel converter slag was developed.

Preparation of Fe3O4/α-MnO2 Magnetic Nanocomposites for Degradation of 2,4-DCP through Persulfate Activation

In this study, Fe3O4 magnetic nanoparticles (MNPs) were loaded on α-MnO2 nanowires using an improved hydrothermal synthesis method combined with an ultrasonic coprecipitation method, the loading ratio was optimized, the efficiency of the prepared Fe3O4/α-MnO2-activated persulfate (PS) system for the degradation of 2,4-dichlorophenol (2,4-DCP) was investigated, and the effects of PS concentration, Fe3O4/α-MnO2 magnetic nanocomposites (MNCs) dosage, pH value and initial pollutant concentration on the degradation of 2,4-DCP were investigated. The results showed that when the initial concentrations of 2,4-DCP, PS, and Fe3O4/α-MnO2 MNCs were 100 mg/L, 30 mmol/L, and 0.4 g/L, the degradation rate of 2,4-DCP reached 96.3% after 180 min of reaction at 30 °C under a neutral condition, and the fitting results showed that the degradation of 2,4-DCP by the Fe3O4/α-MnO2-activated PS system conformed to quasi-first-order kinetics. The degradation of 2,4-DCP by different Fe3O4/α-MnO2-activated PS systems was compared, and a possible PS activation mechanism was proposed. The Fe3O4/α-MnO2 MNCs exhibited excellent reusability, and by introducing Fe3O4/α-MnO2 MNCs as the PS activator into the advanced oxidation process (AOP) system, the electron transfer of Mn(III/IV) and Fe(III/II) on the surface of MNCs was realized, thus greatly improving the reaction efficiency.

Effect of activator/precursor mass ratio on sulfur-doped porous carbon for catalytic oxidation of aqueous organics with persulfate.

Sulfur-doped porous carbon has emerged as promising metal-free catalysts toward persulfate (PS) for catalytic oxidation of aqueous organics. Wherein, thermal pyrolysis with activator activation is very common for the preparation of activated carbon. However, the relationship between the mass ratio of activator/precursor and catalytic efficiency has been rarely reported. Herein, a series of sulfur-doped porous carbons (S-AC) were synthesized by one-step chemical activation of (Poly(phenylene sulphide) (PPS)) with K2CO3 as activator at K2CO3/PPS mass ratio ranging from 0 to 3. The effects of K2CO3/PPS mass ratio on its physicochemical properties and its catalytic performance for p-chlorophenol (PCP) degradation with PS were comprehensively investigated. Experiment results show that sulfur doping enhanced its catalytic activity and the sample synthesized with K2CO3/PPS mass ratio of 2 (S-AC-2) exhibited the best adsorption and catalytic performance toward PS for PCP removal. More importantly, S-AC-2 with PS could efficiently degrade various aqueous toxic organics other than PCP, and S-AC-2 showed superior catalytic activity to many recently reported advanced materials. In addition, the effects of several operate parameters, including reaction temperature, PS concentration, pH, humic acid, and inorganic ions on PCP oxidation were evaluated. By combining with the results of quenching experiments and EPR, the PS activation mechanism over S-AC-2 was revealed. Moreover, the reusability and regenerability of S-AC-2 was also studied. It indicates that S-AC-2 showed inferior reusability, but the catalytic activity of which could be fully recovered through thermal treatment at 600°C for 2h in N2.

Insight into the roles of microenvironment and active site on the mechanism regulation in metal-free persulfate activation process coupling with an electric field

The regulation of the persulfate activation mechanism is highly desirable and meaningful for the treatment of different wastewaters. The role of active sites for mechanism regulation in carbon-driven persulfate activation is still ambiguous due to the complex and easily neglected microenvironment (concentration distributions of organics and oxidants) nearby carbon catalyst. This work aims to reveal the critical roles of active site and microenvironment on the activation mechanism through N-doped modification and application of an electric field (AC/PS/EC). Several N-doped activated carbon catalysts were prepared by activating for different times to adjust the surface active center and adsorption selectivity under an electric field. The contribution ratio of radical pathway and non-radical pathway for organic elimination significantly varied with the concentration distribution of organics and oxidants nearby the microelectrodes. The increased electro-adsorption of persulfate anion was found to be the primary promoting factor for the radical pathway for organic oxidation, resulting in a synergistic increase in degradation rate in the AC/PS/EC system. The quantitative structure-activity relationships analysis also revealed that the electro-adsorption selectivity was dominated by the surface graphitic N and pore structure of catalyst. This study sheds new light on the oxidative pathway regulation to deal with complex wastewater in a flexible and efficient manner.