Persulfate-based Advanced Oxidation Processes Research Articles

Activation of peroxymonosulfate (PMS) by Co3O4 quantum dots decorated hierarchical C@Co3O4 for degradation of organic pollutants: Kinetics and radical-nonradical cooperation mechanisms

Persulfate-based advanced oxidation process (PS-AOP) is a promising technology for in-depth wastewater treatment. Here, Co3O4 quantum dots (QDs) decorated hierarchical C@Co3O4 (C@Co3O4-Q5) was prepared by a facile route. The crystalline structure, micrograph and chemical composition of C@Co3O4-Q5 were characterized by XRD, SEM, TEM and XPS. Taking Rhodamine B (RhB) as a model contaminant, the influences of process parameters on the degradation performance were evaluated. Detailed reaction kinetics investigation indicated that, at elevated temperatures higher than 30 °C, RhB degradation rate approximately follows this expression: r=1.022×107exp(-47850/RT)[RhB][PMS]0.36, whereas the real energies for catalytic activation (Eac) and heat activation (Eah) were 16.231 kJ·mol−1 and 31.62 kJ·mol−1, respectively. Reactive oxygen species (ROS) quenching experiments and EPR tests suggested that not the general held radical SO4− but the downstream OH and the nonradical ROS 1O2 co-contribute to RhB mineralization. Meanwhile, PMS activation mechanisms referring to OH and 1O2 generation were elaborated based on XPS discussion. It was revealed that Co3O4 quantum dots and oxygen functional groups and/or oxygen defects on carbon surface cooperate to generate ROS. Additionally, 5 successive cycles confirmed C@Co3O4-Q5′s high stability and reusability. These findings provided new insights into carbon-loaded QDs catalysts for PMS-mediated micropollutants removal.

Unraveling the mechanisms for persulfate-based remediation of triphenyl phosphate-contaminated soils: Complicated soil constituent effects on the formation and propagation of reactive oxygen species

The continuous accumulation of triphenyl phosphate (TPHP) in soil poses a potential threat to human health. Persulfate-based advanced oxidation processes (SR-AOPs) are promising soil remediation technologies. Naturally occurring soil constituents could interact with persulfate (PS) during soil remediation by SR-AOPs. However, the production and transformation of reactive oxygen species (ROS) by synthetic reactions between PS and different soil constituents, as well as their roles in the pollutants degradation, are still largely unknown. This study systematically investigated the generation of ROS and their roles in degradation of TPHP in soil constituents activated PS process and in soil constituents-heat (50 °C) co-activated PS process. Comprehensive studies including ROS identification, electron paramagnetic resonance analysis, and ROS-generated model systems were carried out. An appreciable degradation rate of TPHP (~21.9%) in soil-PS system and the significant discrepancy in degradation rate (69.0–97.0%) in heat-soil-PS systems with three different soils suggested that soil constituents exhibited complex effects on the activation of PS. The Fe/Mn-minerals in soil effectively activated PS and facilitated TPHP degradation. Specially, the iron redox cycle (Fe(II) ↔ Fe(III)) plays a key role in ROS generation. Small molecular soil organic matter (SOM) rapidly consumed the produced ROS which led to their mineralization, while the remaining macromolecular SOM became more hydrophilic by interaction with ROS. SO4•−, •OH, and 1O2 played major roles directly in TPHP degradation, while O2•− could not degrade TPHP directly but might promote TPHP degradation by reducing Fe(III)- to Fe(II)-minerals or converting to other ROS. This study provides new and deeper insights into the interaction between PS and soil constituents and their roles in organic pollutant degradation in contaminated soil using SR-AOPs.

The use of carbon materials in persulfate-based advanced oxidation processes: A review

The use of carbon materials in persulfate-based advanced oxidation processes: A review

Activation of persulfates by carbonaceous materials: A review

• Structural defects and certain O-groups on surface of C material cause activation. • Synergistic effect takes place for heteroatomic C materials to activate persulfates. • Both radical and non-radical pathways are responsible for the activation. • Application of C materials for the activation is limited but have great potential. In recent years, persulfate-based advanced oxidation processes (PS-AOPs) for removal of organic contaminants from water have gained wide attention. Ever-emerging carbonaceous materials, including pristine carbon materials and their derivatives, heteroatom-doped carbon materials, and carbon materials with metal particles, are demonstrated to be effective in the activation of persulfates (peroxymonosulfate (PMS) and peroxydisulfate (PDS)) to generate free radicals or non-radical active species for degradation of the contaminants. In this paper, mechanisms for the activation of persulfates by carbonaceous materials and their composites are analyzed and summarized. In particular, the synergistic effect for activation improvement in the composites or in the hybrid activation systems is explored. Then the influence of the environmental conditions, such as pH, temperature, inorganic anions and dissolved organic matter, on the activation processes are discussed. Deactivation and regeneration of the carbonaceous materials are discussed as well. Finally, the application of these carbonaceous materials in activating persulfates for remediation of contaminated groundwater and treatment of wastewater are reviewed and the challenges for such applications are proposed.

Synthesis of Fe0/Fe3O4@porous carbon through a facile heat treatment of iron-containing candle soots for peroxymonosulfate activation and efficient degradation of sulfamethoxazole

Developing highly efficient, reusable, non-toxic and low-cost catalysts is of great importance for persulfate-based advanced oxidation processes (AOPs). In this work, ferrocene was mixed into paraffin to prepare a candle, and the iron-containing candle soots were collected and heated at 500 °C~900 °C under N2 atmosphere for 1 h to prepare magnetically recyclable Fe0/Fe3O4@porous carbon (Fe0/Fe3O4@PC) catalysts. The Fe0/Fe3O4@PC-700 obtained after pyrolysis at 700 °C exhibited the best catalytic activity for sulfamethoxazole (SMX) degradation. 10 mg/L SMX could be completely degraded within 10 min by 0.2 g/L of Fe0/Fe3O4@PC-700 and 0.5 mM PMS at pH 5.0. The carbon shell effectively inhibited the Fe leaching of Fe0/Fe3O4@PC-700, and 99.73% of Fe was retained after five consecutive cycles. In the Fe0/Fe3O4@PC-700/PMS system, SMX was degraded through the sulfate radical (SO4·¯), hydroxyl radical (·OH), superoxide radical (O2·¯) dominated radical pathway, and the singlet oxygen (1O2) dominated non-radical pathway. The coexisting inorganic ions and natural organic matters (NOM) in actual water inhibited the degradation of SMX. Finally, four possible degradation pathways were proposed based on the degradation intermediates of SMX. This work provides a facile heat treatment of iron-containing candle soots strategy to prepare the metal@carbon catalysts for PMS-based AOP.

Degradation of ciprofloxacin using UV-based advanced removal processes: Comparison of persulfate-based advanced oxidation and sulfite-based advanced reduction processes

In this study, the degradation of ciprofloxacin (CIP) in wastewater was investigated using UV-based sulfate radical advanced oxidation processes (SR-AOP) and UV-based advanced reduction processes (ARP). More specifically, a comparison of the UV-based persulfate advanced oxidation process (the UV/PS process) and the UV-based sulfite advanced reduction process (the UV/sulfite process) was made. Considering the UV-based SR-AOPs, the UV/PS process was much more efficient than the UV-based peroxymonosulfate advanced oxidation process (the UV/PMS process), with pseudo first order reaction rate constants (kobs) of 0.752 and 0.145 min−1, respectively. For the UV-based ARPs, the UV/sulfite process was the most efficient, compared to the UV/sulfide and the UV/dithionite process (kobs of 0.269, 0.0157 and 0.0329 min−1, respectively). The optimal process parameters for both the UV/PS and the UV/sulfite process were determined and the contribution of the produced reactive species were identified. For the UV/PS process, maximal CIP degradation was found at pH 8, and both OH and SO4− were responsible for CIP degradation. For the UV/sulfite process, H and eaq− were responsible for CIP degradation, with eaq− being the predominant radical at pH 8.5. Although CIP degradation was much faster for the UV/PS process, the UV/sulfite process was determined to be much more efficient in the defluorination of CIP.

Theoretical exploration of VOCs removal mechanism by carbon nanotubes through persulfate-based advanced oxidation processes: Adsorption and catalytic oxidation

Carbon-catalyzed persulfate activation for the removal of gaseous volatile organic compounds (VOCs) has not been reported yet, and the corresponding fundamental mechanisms of VOCs adsorption and the subsequent VOCs degradation remain controversial. In this work, theoretical chemistry calculations were carried out to explore the VOCs removal mechanism by the persulfate-based advanced oxidation processes (P-AOPs) for VOCs removal over single walled carbon nanotubes (SWCNT). This study provided detailed theoretical insights into the SWCNT/P-AOPs for VOCs treatment in terms of adsorption, activation, mineralization, and diffusion of VOCs or peroxymonosulfate (PMS). Various VOCs were found to be preferentially adsorbed onto SWCNT, and the adsorption strength of VOCs was found to be significantly dependent on their polarizability. On the other side, PMS adsorbed on SWCNT could be efficiently activated through accepting π electron in the sp2 carbon matrix of SWCNT rather than the electrons at dangling bonds to generate •OH radicals attributed to the strong interaction between PMS and SWCNT. Formaldehyde was then taken as an example to evaluate the catalytic degradation pathways via SWCNT/P-AOPs. Under the attack of •OH radicals, the ultrafast degradation pathway of formaldehyde with no byproduct CO was identified with ultralow reaction energy barrier and large energy release. In addition, factors affecting the adsorption of organic compounds were identified and the detailed PMS activation pathway was present directly in this work. Above all, this work extended the carbons/P-AOPs system to VOCs abatement and presented systematic evidences for the essential mechanisms associated with VOCs adsorption and PMS activation by SWCNT, and the corresponding removal pathway and mechanism were also understood.

Iron-based catalysts for persulfate-based advanced oxidation process: Microstructure, property and tailoring

• Influence factors of AOPs of iron-based catalysts were comprehensively summarized. • Active species and catalytic mechanism of iron-based catalysts were explored. • The key issues and possible research directions have made some corresponding outlooks. Sulfate radicals (SO 4 − )-based advanced oxidation processes have obtained far-reaching attention due to their high catalytic activity and selectively for intricate water environmental pollutants. The couple of cheap and readily available iron-based materials and peroxymonosulfate (PMS) or persulfate (PS) is an effective measure to generate incalculabe reactive sulfate radicals. The article analyzed the latest research progress on different typical heterogeneous iron-based catalysts for PMS or PS activation. The microstructure and electrical properties of these catalysts and the effects of different tailoring engineering approaches (such as structure defect, heteroatom doping, and rugulation of pore structure, etc) in PMS or PS activation were summarized. In addition, the environmental factors of iron-based materials-PMS (PS) systems in organic pollutants degradation and related advanced oxidation processes were also summarized. Finally, critical discussion and possible future prospects on challenges related to degradation mechanism exploration, potential catalysts development as well as practical catalytic system application were also proposed.

A facile method to fabricate AC/CuO for efficient removal of organic pollutants by adsorption and persulfate-based advanced oxidation processes

Abstract Activated carbon/CuO (AC/CuO) composites were prepared through a facile one-step hydrothermal method and used as a bifunctional material for adsorption and catalysis degradation of bisphenol A (BPA). The composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray powder diffraction (XRD). The obtained AC/CuO exhibited excellent adsorption and catalytic performance. The maximum adsorption capacity of BPA on the AC/CuO was 319.03 mg/g according to the Langmuir fitting. At an initial BPA concentration of 20 mg/L, the BPA degradation efficiencies were maintained above 96% for 15 min by using 20 mg/L AC/CuO and 2 mM peroxymonosulfate (PMS). Moreover, the relationship between adsorption and catalytic degradation was also investigated. The results indicated that the pre-adsorption disfavored the degradation reaction. This work not only provides a novel preparation method for AC/CuO catalyst, but also gives a deeper insight into the mechanisms between adsorption and catalytic degradation.

SONOPHOTOCHEMICAL OXIDATION OF ORGANIC CONTAMINANTS IN AQUEOUS SOLUTIONS USING PERSULFATE

In present work, we have studied the kinetic fundamentals of sonophotochemical oxidation of emerging organic contaminants, atrazine and bisphenol A, in model aqueous solutions, simultaneously exposed to high-frequency ultrasound (US, 1.7 MHz) and ultraviolet light-emitting diodes (UV LEDs, 365 nm) in the absence and presence of persulfate (S2O82-) oxidant. Synergistic indices were calculated to assess a synergistic effect in the hybrid oxidation systems. It was found that the hybrid system {UV/US/S2O82-} exhibited the synergistic effect and was the most efficient for degrading bisphenol A in a raw: UV/US/S2O82- > UV/S2O82- > US/UV > US/S2O82- >> UV > US. In case of atrazine, no ultrasound effect was observed and the efficiencies of {UV/US/S2O82-} and {UV S2O82-} systems in terms of degradation rates were similar. In these oxidation systems, more than 90% of a contaminant was removed after 30 min treatment. Meanwhile, degradation rates for atrazine were higher than those wich were found for bisphenol A. This indicates a predomination of sulfate anion radicals, which react with bisphenol A rather slowly compared to atrazine. A synergism was also found under sonophotolysis of both contaminants without persulfate; however, this process requires a more prolonged irradiation time (~20% degraded in 40 min), hence, it is less energy-effective. The obtained results are promising for application of UV LEDs and high-frequency ultrasound in persulfate-based advanced oxidation processes to degrade organic contaminants in natural water and wastewater.

One-pot thermal polymerization route to prepare N-deficient modified g-C3N4 for the degradation of tetracycline by the synergistic effect of photocatalysis and persulfate-based advanced oxidation process

N-deficient g-C3N4 (CNx) photocatalyst was synthesized via a simple one-step thermal polymerization of urea and oxamide for the degradation of tetracycline (TC) under visible-light irradiation in the presence of persulfate (PS) activation. The microstructure and morphology of CNx were investigated by a host of characteristic technologies. The experimental result revealed that CNx/PS system displays a high efficiency in the photocatalytic process of TC degradation. The effects of different environmental factors (catalyst dose, PS dose, initial TC concentration and initial pH) on the degradation of the system were investigated. The possible intermediates products were discussed based on the liquid chromatography-mass spectrometry (LC-MS) analysis. Moreover, the toxicity of the TC solution over CNx/PS synergistic photocatalytic system was studied by the culture of bean sprouts, demonstrated that the aquatic toxicity of the TC after degradation of the system was effectively reduced.

Efficacy of persulfate-based advanced oxidation process (US/PS/Fe3O4) for ciprofloxacin removal from aqueous solutions

Research evidence has shown that pollution of surface and underground waters is the leading sources of environmental and health-related problems. Disposed unused therapeutic drugs have been known to contaminate underground water and also offer drug resistance to infection-causing bacterial. This research seeks to evaluate the use of US/PS/Fe3O4 for the removal of ciprofloxacin (CIP-F) from aqueous solutions. The research also seeks to obtain the optimum set of conditions about which the highest removal efficiency of CIP-F is obtained by monitoring the used pH, Fe3O4 nanoparticles (NPs) concentration, PS concentration, CIP-F concentration, and contact time. The analysis was done using a UV–Vis spectrophotometer (Cecil model CE102) set at 280 nm. The result shows that a 98.43% removal efficiency is achievable after optimization if the separation parameters were set to the optimum conditions (pH = 5, CIP-F concentration = 200 mg/L, PS concentration = 0.15 mol/L, Fe3O4 concentration = 0.01 g/L and contact time = 45 min). The reaction was also observed to follow the pseudo-first-order reaction model. Since the results obtained show that US/PS/Fe3O4 can effectively and efficiently aid the surface adsorption of CIP-F from aqueous solutions, it is therefore recommended based on experimental findings that US/PS/Fe3O4 be used for removing CIP-F from effluents.

Metal-free carbocatalysis for persulfate activation toward nonradical oxidation: Enhanced singlet oxygen generation based on active sites and electronic property

In recent years, metal-free carbocatalysis and persulfate-based advanced oxidation processes have appealed much attention due to the high efficiency and environmental sustainability. This study aimed to investigate catalytic performance of carbon nanofibers (CNFs) on persulfate for removal of 2,4-dichlorophenol and elucidate the intrinsic mechanism of PS activation. Singlet oxygen (1O2) generation was hypothesized to be the dominant pathway for the nonradical organic oxidation. Carbonyl groups and structural defects were determined as the primary active sites via CNFs modification. Density functional theory (DFT) calculations further unearthed that armchair and zigzag edges were favorable to electron transfer and vacancy sites enhanced PS adsorption on CNFs. A higher density of states (DOS) with lower π and σ electronic binding energies would make CNFs more active, and a lower work function (Ф) would lead to a lower inner electron excitation energy barrier to enhance the electron transfer. The degradation pathways were finally determined by combining mass spectrum analysis and DFT calculations (Fukui function), where 1O2 molecules were likely to attack the Cl and O atoms.

The Intrinsic Nature of Persulfate Activation and N-Doping in Carbocatalysis.

Persulfates activation by carbon nanotubes (CNT) has been evidenced as nonradical systems for oxidation of organic pollutants. Peroxymonosulfate (PMS) and peroxydisulfate (PDS) possess discrepant atomic structures and redox potentials, while the nature of their distinct behaviors in carbocatalytic activation has not been investigated. Herein, we illustrated that the roles of nitrogen species in CNT-based persulfate systems are intrinsically different. In PMS activation mediated by nitrogen-doped CNT (N-CNT), surface chemical modification (N-doping) can profoundly promote the adsorption quantity of PMS, consequently elevate potential of derived nonradical N-CNT-PMS* complexes, and boost organic oxidation efficiency via an electron-transfer regime. In contrast, PDS adsorption was not enhanced upon incorporating N into CNT due to the limited equilibrium adsorption quantity of PDS, leading to a relatively lower oxidative potential of PDS/N-CNT system and a mediocre degradation rate. However, with equivalent persulfate adsorption on N-CNT at a low quantity, PDS/N-CNT exhibited a stronger oxidizing capacity than PMS/N-CNT because of the intrinsic higher redox potential of PDS than PMS. The oxidation rates of the two systems were in great linearity with the potentials of carbon-persulfate* complexes, suggesting N-CNT activation of PMS and PDS shared the similar electron-transfer oxidation mechanism. Therefore, this study provides new insights into the intrinsic roles of heteroatom doping in nanocarbons for persulfates activation and unveils the principles for a rational design of reaction-oriented carbocatalysts for persulfate-based advanced oxidation processes.

Persulfate-Based Advanced Oxidation: Critical Assessment of Opportunities and Roadblocks.

Reports that promote persulfate-based advanced oxidation process (AOP) as a viable alternative to hydrogen peroxide-based processes have been rapidly accumulating in recent water treatment literature. Various strategies to activate peroxide bonds in persulfate precursors have been proposed and the capacity to degrade a wide range of organic pollutants has been demonstrated. Compared to traditional AOPs in which hydroxyl radical serves as the main oxidant, persulfate-based AOPs have been claimed to involve different in situ generated oxidants such as sulfate radical and singlet oxygen as well as nonradical oxidation pathways. However, there exist controversial observations and interpretations around some of these claims, challenging robust scientific progress of this technology toward practical use. This Critical Review comparatively examines the activation mechanisms of peroxymonosulfate and peroxydisulfate and the formation pathways of oxidizing species. Properties of the main oxidizing species are scrutinized and the role of singlet oxygen is debated. In addition, the impacts of water parameters and constituents such as pH, background organic matter, halide, phosphate, and carbonate on persulfate-driven chemistry are discussed. The opportunity for niche applications is also presented, emphasizing the need for parallel efforts to remove currently prevalent knowledge roadblocks.

Reclamation of hospital secondary treatment effluent by sulfate radicals based–advanced oxidation processes (SR-AOPs) for removal of antibiotics

Nowadays, pollution of water resources by emerging resistant contaminants such as antibiotics is a growing issue. The limitations in conventional treatment methods for the removal of emerging contaminants intrigued the researcher to propose advanced treatment methods. Moreover, the high values of carbon-based compounds in wastewater and also treated effluent arise issues in treatment processes. Thus, this study aims to determine the removal of amoxicillin and ciprofloxacin from hospital effluent using an ultraviolet-activated persulfate-based advanced oxidation process. The effect of the study variables including persulfate concentration (2.5–10 mg L−1), pH(4–11), initial concentration of antibiotics (1,10 mg L−1) and reaction time (2.5–120 min) was investigated on the removal of antibiotics. Moreover, the chemical reaction kinetics and mineralization rate were determined and the interference effect of various ions was investigated. The results showed that the highest removal of ciprofloxacin and amoxicillin were observed to be respectively 99.9% and 99.26% at the reaction time of 60 min, initial concentration of 1 mg L−1and persulfate concentration of 10 mg L−1. The antibiotics removal rate increased as their initial concentration decreased Further, increase of the persulfate concentration and reaction time increased the removal rate. Degradation kinetics of ciprofloxacin and amoxicillin followed the pseudo-first-order equation. The use of persulfate did not significantly increase the sulfate and nitrate content of wastewater. Moreover, mineralization was not performed in the ultraviolet/persulfate process for both antibiotics. The results showed that the ultraviolet-activated persulfate-based advanced oxidation process can be used as an appropriate method for the removal of antibiotics in complicated aqueous media such as hospital effluent.

Structure-dependent catalysis of cuprous oxides in peroxymonosulfate activation via nonradical pathway with a high oxidation capacity

Research interests have been recently thrust into the nonradical reactions in persulfate-based advanced oxidation processes (AOPs), whilst the underlying mechanism of the nonradical pathway remains ambiguous especially in metal-based AOPs systems. In this study, we investigated the reactivity of cuprous oxide (Cu2O) for activating peroxymonosulfate (PMS) to decompose diverse organic contaminants. Cu2O exhibited a strong catalytic dependence on the crystal morphology, and cubic Cu2O was more reactive than the octahedral and rhombic dodecahedral structures for catalytic degradation of bisphenol A with PMS. Chemical quenching tests, electron paramagnetic resonance (EPR), solvent exchange and selective oxidation experiment were corporately conducted to illustrate that Cu2O-catalyzed PMS did not produce free radicals or singlet oxygen. In contrast, a surface-confined metastable intermediate would be formed via outer-sphere interactions between PMS and Cu2O, which directly attacked the organic substrate. Such a reaction pathway is intrinsically distinct from the electron-shuttling regime in carbon (or noble metal)/persulfate systems via the conductive surface of the catalyst, and the outer-sphere interactions let the activated PMS demonstrate a higher oxidizing capacity toward organic contaminants. Therefore, this study dedicates to providing new insights into the copper-catalyzed AOPs and vital supplementary to the ongoing dialogue of the nonradical catalysis in persulfate-based oxidation.

Chemiluminescence as a New Indicator for Monitoring Hydroxylated Intermediates in Persulfate-Based Advanced Oxidation Processes

The formation of hydroxylated intermediates is the first step in the persulfate-based advanced oxidation processes (AOPs) and depends directly on the oxidation degree of recalcitrant pollutants. Th...

Degradation of benzotriazole by sulfate radical-based advanced oxidation process

ABSTRACT Benzotriazole (BTA) is a recalcitrant contaminant that is widely distributed in aquatic environments. This study explored the effectiveness of sulfate radical-based advanced oxidation process in degrading BTA (SR-AOP). The sulfate radical was generated by heat activation of persulfate (PS). Our results show alkaline pH promoted the BTA degradation. The solution pH also affected the speciation of total radicals. Sulfate radical () predominated at acidic pH while hydroxyl radical (HO•) predominated at basic pH. High temperature, high PS concentration and low BTA concentration promoted the BTA degradation. Influence of water matrix constituents on the reaction kinetics was assessed. We found that ≤10 mM of Cl− promoted the reaction, but 100 mM Cl− inhibited it. was similar to Cl−. Br− and inhibited the reaction while did not affect the reaction. of ≤10 mM did not affect the reaction, but 100 mM of inhibited it. Eleven degradation intermediates were identified using ultra-high solution Orbitrap mass spectrometry. Based on the intermediates identified, possible reaction pathways were proposed. Overall, SR-AOP can effectively mineralize BTA, but water matrix constituents greatly influenced the reaction kinetics and thus should be carefully considered for its practical application. Abbreviations: BTA, benzotriazole; PS, persulfate; PMS, peroxymonosulfate; SPC, sodium percarbonate; AOP, advanced oxidation process; PS-AOP, persulfate-based advanced oxidation process; SR-AOP, sulfate radical-based advanced oxidation process; TAP, thermally activated persulfate; TOC, total organic carbon; TBA, tert-butyl alcohol

Magnetic nitrogen-doped sludge-derived biochar catalysts for persulfate activation: Internal electron transfer mechanism

Persulfate-based advanced oxidation process is a powerful countermeasure for water remediation, where effective and low-cost catalysts are still needed. Herein, a one-pot synthetic method for magnetic nitrogen-doped sludge biochar (MS-biochar) was presented, which exhibited better catalytic property with PDS for tetracycline degradation than typical graphitic carbon (graphite powder, graphene oxide and multiwalled carbon nanotubes) and two other types biochars. EDAX manifested the uniform dispersion of elements in MS-biochar. Similar to “top-down”, a research thought from whole to part of MS-biochar for contribution measurement was presented, where acid-soluble substance (ASS) was the most important contributor for MS-400/600 while carbon matrix (CM) was dominant for MS-800. Quenching and EPR demonstrated a free-radicals pathway in MS-biochar/PDS, where ASS mainly assumed to be effective for SO4− and CM was primarily committed to OH generation. EDAX, XPS and Raman studies proved three kinds of catalytic sites, namely the iron compounds, doped nitrogen and graphitic carbon. And their activating mechanism were discussed where one internal electron migration path (from sp3 to nanocrystalline sp2 carbon) has been first proposed. Reusability, metal leaching detection and pharmaceutical wastewater application indicated the potential of MS-biochar. This work not only presents a potential resource-based disposal of sewage sludge, a novel research thought from whole to part for materials performance measurement, but also provides guidance for carbon materials’ design for persulfate activation, especially for sp2 and sp3 co-hybridized carbons.