Homogeneous catalytic activation of peroxymonosulfate and heterogeneous reductive regeneration of Co2+ by MoS2: The pivotal role of pH

Hierarchical Anion Exchange and Reverse Electron Transfer in Layered Double Hydroxides/Peroxymonosulfate System for Roxarsone Elimination

Roxarsone (ROX) is the main form of arsenic pollution in the world, and developing effective methods for its elimination is beneficial to human health and the ecological environment. Herein, we report glutaraldehyde cross-linked chitosan-encapsulated CoCe-LDH (layered double hydroxides) as an outstanding catalyst for the advanced oxidation of ROX and the efficient adsorption of inorganic arsenic. 100% of ROX and more than 98.5% of As(III)/As(V) were eliminated, and over 99.3% of remaining inorganic arsenic was oxidized to low-toxicity As(V) in the peroxymonosulfate (PMS) activation system, and some specific properties of LDH are considered the main reasons. The hierarchical anion exchange has been confirmed to be beneficial for constructing a high-concentration PMS interlayer microenvironment. The unique reverse electron transfer process induced 100% selective production of singlet oxygen. This work not only develops an advanced ROX removal method but also provides a new understanding of the LDH-based advanced oxidation process.

Efficient ofloxacin degradation via peroxymonosulfate activation using an S-scheme MoS2/Co3O4 heterojunction composite under visible light: Performance and mechanistic insights

Sulfate-radical-mediated photocatalysis technology peroxymonosulfate (PMS) activation via visible light irradiation shows great promise for water treatment applications. However, its effectiveness largely depends on the bifunctional performance of photocatalysis and PMS activation provided by the catalysts. In this study, we successfully synthesized a novel S-scheme MoS2/Co3O4 (MC) heterojunction composite by a hydrothermal method and employed it for the first time to activate PMS for ofloxacin (OFX) degradation under visible light irradiation. The MC-5/PMS/Vis system achieved an impressive 85.11% OFX degradation efficiency within 1 min and complete OFX removal within 15 min under optimal conditions, with an apparent first-order kinetics rate constant of 0.429 min-1. Reactive species trapping experiments and electron spin resonance analysis identified 1O2, h+, and •O2- as the primary active species responsible for OFX degradation. Photoelectrochemical analyses and density functional theory calculations indicated the formation of a built-in electric field between MoS2 and Co3O4, which enhanced the separation and migration of photoinduced carriers. Additionally, the Co-Mo interaction further increased the yield of dominant reactive species, thereby boosting photocatalytic activity. This work underscores the potential of visible-light-assisted PMS-mediated photocatalysis using Co3O4-based catalysts for effective pollutant control.

Activation of Peroxymonosulfate by Co-Ni-Mo Sulfides/CNT for Organic Pollutant Degradation

To explore advanced oxidation catalysts, peroxymonosulfate (PMS) activation by Co-Ni-Mo/carbon nanotube (CNT) composite catalysts was investigated. A compound of NiCo2S4, MoS2, and CNTs was successfully prepared using a simple one-pot hydrothermal method. The results revealed that the activation of PMS by Co-Ni-Mo/CNT yielded an exceptional Rhodamine B decolorization efficiency of 99% within 20 min for the Rhodamine B solution. The degradation rate of Co-Ni-Mo/CNT was 4.5 times higher than that of Ni-Mo/CNT or Co-Mo/CNT, and 1.9 times as much than that of Co-Ni/CNT. Additionally, radical quenching experiments revealed that the principal active groups were 1O2, surface-bound SO4•-, and •OH radicals. Furthermore, the catalyst exhibited low metal ion leaching and favorable stability. Mechanism studies revealed that Mo4+ on the surface of MoS2 participated in the oxidation of PMS and the transformation of Co3+/Co2+ and Ni3+/Ni2+. The synergism between MoS2 and NiCo2S4 reduces the charge transfer resistance between the catalyst and solution interface, thus accelerating the reaction rate. Interconnected structures composed of metal sulfides and CNTs can also enhance the electron transfer process and afford sufficient active reaction sites. Our work provides a further understanding of the design of multi-metal sulfides for wastewater treatment.

Superior performance of oxygen vacancy-enriched Cu-Co3O4/urushiol-rGO/peroxymonosulfate for hypophosphite and phosphite removal by enhancing singlet oxygen

The treatment of wastewater containing hypophosphite [P(I)] and phosphite [P(III)] is challenged by limitations of traditional Fenton oxidation such as low efficiency, secondary pollution and high costs. This study introduced a facile solvent-thermal method to synthesize Cu-Co3O4 nanoparticles uniformly loaded on graphene (Cu-Co3O4/U-rGO) through the reduction and coordination effects of urushiol (U). As prepared Cu-Co3O4/U-rGO exhibited excellent activity in activating peroxymonosulfate (PMS) for the oxidation of P(I)/P(III) to phosphate [P(V)] (0.229 min-1), along with high stability and reusability (91.5 % after 6 cycles), low metal leaching rate (Co: 0.2 mg/L, Cu: 0.05 mg/L), insensitivity to common anions in water and a wide pH range (3-11). The activation mechanism involved the synergistic effects from both urushiol and graphene, which promoted redox of Cu+/Cu2+ and Co2+/Co3+ and induced abundant oxygen vacancies for PMS activation to produce singlet oxygen. Furthermore, the Cu-Co3O4/U-rGO/PMS was also excellent in the oxidative removal of organic phosphorus. This study is expected to advance strategies for the treatment of P(I)/P(III)-rich wastewater and provide new insights for the development of low-cost, highly efficient heterogeneous catalysts with abundant oxygen vacancies.

Efficient carbamazepine degradation by modified copper tailings and PMS system: Performance evaluation and mechanism

It is a green and sustainable path to establish cheap solid waste-based catalyst to establish peroxymonosulfate (PMS) catalytic system for the degradation of carbamazepine (CBZ) in water. In this study, durable copper tailing waste residue-based catalyst (CSWR) was prepared, and efficient CSWR/PMS system was constructed for catalytic degradation of CBZ for first time. The morphology and structure of CSWR changed from clumps to porous and loose amorphous by alkali leaching and medium temperature calcination. The reconstructed surface of the CSWR exposes more active sites promotes the catalytic reaction and increases the degradation rate of CBZ by more than 39.8 times. And the CSWR/PMS achieved a CBZ removal of nearly 99.99 % in 20 min. In particular, perovskite-type iron-calcium compounds were formed, which stimulated the production of more HO• and SO4•- in the system. DFT calculation shows that CSWR has stronger adsorption energy and electron transfer ability to PMS molecules, which improved the degradation efficiency of the system. In general, this study proposed a means of high-value waste utilization, which provided a new idea for the preparation of solid waste based environmental functional materials and is expected to be widely used in practical wastewater treatment.

Enhanced electron transfer for activation of peroxymonosulfate via MoS2 modified iron-based perovskite

The increasing use of fluoroquinolone antibiotics, which are found in various environmental media, is a constant threat to ecological safety and human health. In this paper, SrFeO3@MoS2 heterogeneous catalyst was prepared to activate peroxymonosulfate (PMS) for the degradation of levofloxacin (LVO). The characteristics of SrFeO3@MoS2 samples were studied and the optimum conditions for the removal of LVO by SrFeO3@MoS2/PMS system were investigated. The removal of LVO by the SrFeO3@MoS2-0.3/PMS system could reach 96.06% within 20 min of reaction. The effect of inorganic anions (SO42-, Cl-, NO3- and H2PO4-) commonly found in actual water bodies on catalytic reaction was explored. The reusability investigation revealed that the catalyst could still remove 88.06% of LVO within 20 min after four cycles. Moreover, SO4•-, •OH and 1O2 were identified by Electron Paramagnetic Resonance (EPR) tests and scavenger experiments, where the SO4•- and •OH were dominant reactive species. Combining with the XPS characterisation, the activation mechanism of SrFeO3@MoS2-0.3/PMS was proposed, and the oxygen vacancies and transition metals on the sample surface were active sites of PMS activation. Furthermore, the possible degradation pathways of LVO were well-established based on the detected intermediates.

Carbon nanotube supported cobalt nickel sulphide nano-catalyst for degradation of chloroquine phosphate with peroxymonosulphate

Carbon nanotubes supported cobalt nickel sulphide nanoparticles (nano-NiCo2S4@CNTs) were successfully prepared by a hydrothermal method as heterogeneous catalyst which can be used as an activator of peroxymonosulphate (PMS) for the degradation of chloroquine phosphate (CQP). Based on characterisation techniques, the prepared catalyst has excellent surface properties and structural stability. When different concentrations of CQP were treated with 0.2 g/L nano-NiCo2S4@CNTs and 1.0 mM PMS, the highest degradation rate could reach 99.86% after 30 min. Under the interference of pH, common anions and humic acid in the water environment, the reaction system can still achieve high degradation efficiency, showing excellent anti-interference ability and practical applicability. Furthermore, in the nano-NiCo2S4@CNTs/PMS system, according to the identification results of reactive oxygen species, the free radical and non-free radical pathway are responsible for the degradation of CQP, and the PMS mechanism activation was comprehensively proposed. Twelve intermediate products were detected in the degradation process, and the possible degradation pathways of CQP were proposed. This toxicity analysis demonstrates that the intermediate products formed during CQP degradation pose lower environmental risks compared to the original pollutant. In addition, after using the catalyst four cycles, the removal efficiency of CQP remains above 80%, indicating the excellent reusability and low metal ion leaching characteristics. Therefore, the nano-NiCo2S4@CNTs synthesised in this research has broad application prospects in activating PMS for wastewater treatment.

Sulfur vacancy rich MoS2/FeMoO4 composites derived from MIL-53(Fe) as PMS activator for efficient elimination of dye: Nonradical 1O2 dominated mechanism

A novel MoS2/FeMoO4 composite was synthesized for the first time by introducing an inorganic promoter MoS2 into the MIL-53(Fe)-derived PMS-activator. The prepared MoS2/FeMoO4 could effectively activate peroxymonosulfate (PMS) toward 99.7% of rhodamine B (RhB) degradation in 20 min, and achieve a kinetic constant of 0.172 min-1, which is 10.8, 43.0 and 3.9 folds higher than MIL-53, MoS2 and FeMoO4 components, respectively. Both Fe(II) and sulfur vacancies are identified as the main active sites on catalyst surface, where sulfur vacancies can promote adsorption and electron migration between peroxymonosulfate and MoS2/FeMoO4 to accelerate peroxide bond activation. Besides, the Fe(III)/Fe(II) redox cycle was improved by reductive Fe0, S2- and Mo(IV) species to further boost PMS activation and RhB degradation. Comparative quenching experiment and in-situ electron paramagnetic resonance (EPR) spectra verified that SO4•-, •OH, 1O2 and O2•- were produced in the MoS2/FeMoO4/PMS system, while 1O2 dominates RhB elimination. In addition, the influences of various reaction parameters on RhB removal were examined and the MoS2/FeMoO4/PMS system exhibits good performance over a wide pH and temperature range, as well as coexistence with common inorganic ions and humic acid (HA). This study provides a new strategy for preparing MOF-derived composite with simultaneous introduction of MoS2 promotor and rich sulfur vacancies, and enables new insight into radical/nonradical pathway in PMS activation process.

Cobalt-doped molybdenum disulfide for efficient sulfite activation to remove As(III): Preparation, efficacy, and mechanisms

The sulfite(S(IV))-based advanced oxidation process has attracted significant attention in removing As(III) in the water matrix for its low-cost and environmental-friendly. In this study, a cobalt-doped molybdenum disulfide (Co-MoS₂) nanocatalyst was first applied to activate S(IV) for As(III) oxidation. Some parameters including initial pH, S(IV) dosage, catalyst dosage, and dissolved oxygen were investigated. The experiment results show that >Co(II) and >Mo(VI) on the catalyst surface promptly activated S(IV) in the Co-MoS₂/S(IV) system, and the electron transfer between Mo, S, and Co atoms accelerated the activation. SO₄^•- was identified as the main active species for As(III) oxidation. Furthermore, DFT calculations confirmed that Co doping improved the MoS₂ catalytic capacity. This study has proven that the material has broad application prospects through reutilization test and actual water experiments. It also provides a new idea for developing bimetallic catalysts for S(IV) activation.

Peroxymonosulfate activated by natural porphyrin derivatives for rapid degradation of organic pollutants via singlet oxygen and high-valent iron-oxo species

The activation of peroxymonosulfate (PMS) by sodium ferric chlorophyllin (SFC), a natural porphyrin derivative extracted from chlorophyll-rich substances, was systematically investigated for facile degradation of bisphenol A (BPA). SFC/PMS is capable of degrading 97.5% of BPA in the first 10 min with the initial BPA concentration of 20 mg/L and pH = 3, whereas conventional Fe²⁺/PMS could only remove 22.6% of BPA under identical conditions. It demonstrates a prominent flexibility to a broad pH range of 3-11 with complete pollutant degradation. A remarkable tolerance toward concomitant high concentration of inorganic anions (100 mM) was also observed, among which (bi)carbonates can even accelerate the degradation. The nonradical oxidation species, including high-valent iron-oxo porphyrin species and ¹O₂, are identified as dominant species. Particularly, the generation and participation of ¹O₂ in the reaction is evidenced by experimental and theoretical methods, which is vastly different from the previous study. The specific activation mechanism is unveiled by density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. The results shed light on effective PMS activation by iron (III) porphyrin and the proposed natural porphyrin derivative would be a promising candidate for efficient abatement of recalcitrant pollutants toward complicated aqueous media in wastewater treatment.

Insight into electrochemically boosted trace Co(II)-PMS catalytic process: Sustainable Co(IV)/Co(III)/Co(II) cycling and side reaction blocking

A novel homogeneous electrocatalytic system was constructed by current-assisted trace Co(II) activating PMS (ECP) to remove reactive blue 19 (RB19). More than 93 % of RB19 was rapidly removed with only a trace dose, and the PMS was 98.35 % utilized during the reaction. By exploring the active species and analyzing the PMS consumption, it was found that current strongly accelerated the Co(III)/Co(II) redox cycle by providing electrons to Co(III), and inhibited the side reaction thus improving the PMS utilization. Electric energy per order was very low, only 0.26 kWh·m³. Radicals (SO₄^•-) and non-radicals (Co(III), Co(IV) and ¹O₂) participated in ECP system, in which SO₄^•- was dominant. By excluding the other three precursors (PMS, •OH and O₂^•-), the side reaction product SO₅^•- was identified as the source of ¹O₂ in ECP system. Combining chelating agent EDTA and chemical probe PMSO, Co(IV) was considered formed by single and double charge transfer. Five degradation pathways of RB19 were proposed using mass spectrometry and DFT calculation. The ecotoxicity and mutagenicity of RB19 and its transformation products were predicted using software simulation. These studies provided an interesting insights into the synergistic Co(II)-PMS systems and offered a new strategy for electrochemical processes.

Remediation of environmentally persistent organic pollutants (POPs) by persulfates oxidation system (PS): A review

Over the past few years, persistent organic pollutants (POPs) exhibiting high ecotoxicity have been widely detected in the environment. Persulfate-oxidation hybrid system is one of the most widely used novel advanced oxidation techniques and is based on the persulfate generation of SO₄^-∙ and ∙OH from persulfate to degrade POPs. The overarching aim of this work is to provide a critical review of the variety of methods of peroxide activation (e.g., light activated persulfate, heat-activated persulfate, ultrasound-activated persulfate, electrochemically-activated persulfate, base-activated persulfate, transition metal activated persulfate, as well as Carbon based material activated persulfate). Specifically, through this article we make an attempt to provide the important characteristics and uses of main activated PS methods, as well as the prevailing mechanisms of activated PS to degrade organic pollutants in water. Finally, the advantages and disadvantages of each activation method are analyzed. This work clearly illustrates the benefits of different persulfate activation technologies, and explores persulfate activation in terms of Sustainable Development Goals, technical feasibility, toxicity assessment, and economics to facilitate the large-scale application of persulfate technologies. It also discusses how to choose the most suitable activation method to degrade different types of POPs, filling the research gap in this area and providing better guidance for future research and engineering applications of persulfates.

Comments on "Facilely synthesized cobalt doped hydroxyapatite as hydroxyl promoted peroxymonosulfate activator for degradation of Rhodamine B"

In recent years, researchers have devoted themselves to developing composites containing cobalt as highly active heterogeneous catalysts of persulfate. Most of them reported that the catalytic degradation processes of organic pollutants were accompanied by the leaching of cobalt ions, but only a few studies considered the contribution of the dissolved cobalt ion to the degradation of organic compounds. A research paper in Journal of Hazardous Materials reported a study on synthesis, application and catalytic mechanisms of cobalt doped hydroxyapatite (Co-HAP) for Rhodamine B (RhB) degradation. We find that non-main catalytic mechanisms were listed and that the effect of Co-HAP was overestimated.

WS2 significantly enhances the degradation of sulfachloropyridazine by Fe(III)/persulfate

The use of antibiotics has become an indispensable part of the production and life of human society. Among them, sulfonamide antibiotics widely used in humans and animals are considered to be one of the most crucial antibiotics. However, antibiotics are difficult to degrade naturally, leading to an accumulation in the environment and a potential hazard to human health. In this paper, WS₂ as a co-catalyst could reduce trace Fe(III) to Fe(II) which exhibited a great activating ability to PS through the exposed W(IV) active sites, and formed the Fe(III)/Fe(II) cycle to degrade sulfachloropyridazine (SCP) continuously. This paper systematically discussed the degradation of SCP under different conditions in the PS/WS₂/Fe(III) system, including the amount of WS₂, Fe(III) concentration, PS concentration, initial pH, natural organic matter (NOM) and common anions (NO₃^-, Cl^-, HCO₃^-, HPO₄^2- and H₂PO₄^-). The experimental results showed that PS/WS₂/Fe(III) system possessed a strong degradation ability for SCP in a wide pH range. NO₃^- and Cl^- could promote the degradation of SCP a little. HCO₃^-, HPO₄^2- and H₂PO₄^- could significantly inhibit the degradation of SCP. The main types of free radicals that degraded SCP were explored. In addition, the stability and reusability of WS₂ were examined, and two possible degradation pathways of SCP were proposed.

Effective peroxymonosulfate activation by natural molybdenite for enhanced atrazine degradation: Role of sulfur vacancy, degradation pathways and mechanism

In this study, natural molybdenite (MoS₂) was applied to activate peroxymonosulfate (PMS) for the removal of atrazine (ATZ) and its degradation mechanism was investigated. Molybdenite exhibits superior catalytic performance. The best condition for atrazine degradation efficiency (>99%) was obtained with molybdenite concentration of 0.4 g/L, PMS concentration of 0.1 mM, and ATZ concentration of 12 μM within 10 min under experimental conditions. Electron paramagnetic resonance (EPR) test and chemical probe test further proved that HO^• and SO₄^•- played important roles in the molybdenite/PMS system, and SO₄^•- was dominant. Meanwhile, Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) tests showed that sulfur vacancies and edge sulfur played important roles in the system. Edge sulfur was conducive to Mo⁴⁺ exposure, while sulfur vacancy facilitated electron transfer and reduced Mo⁶⁺ back to Mo⁴⁺. Combined with DFT calculation, the role of sulfur in the degradation process was verified. Besides, five ATZ degradation pathways were proposed. Finally, the degradation ability of the molybdenite/PMS system for different pollutants and in actual water bodies was also explored. This work provided ideas for exploring the degradation of organic contaminants by natural minerals.

Efficient removal of antibiotic-resistant bacteria and intracellular antibiotic resistance genes by heterogeneous activation of peroxymonosulfate on hierarchical macro-mesoporous Co3O4-SiO2 with enhanced photogenerated charges

Antibiotic resistance genes (ARGs) and their host antibiotic-resistant bacteria (ARB) are widely detected in the environment and pose a threat to human health. Traditional disinfection in water treatment plants cannot effectively remove ARGs and ARB. This study explored the potential of a heterogeneous photo-Fenton-like process utilizing a hierarchical macro-mesoporous Co₃O₄-SiO₂ (MM CS) catalyst for activation of peroxymonosulfate (PMS) to inactivate ARB and degrade the intracellular ARGs. A typical gram-negative antibiotic-resistant bacteria called Pseudomonas sp. HLS-6 was used as a model ARB. A completed inactivation of ARB at ∼10⁷ CFU/mL was achieved in 30 s, and an efficient removal rate of more than 4.0 log for specific ARGs (sul1 and intI1) was achieved within 60 min by the MM CS-based heterogeneous photo-Fenton-like process under visible light and neutral pH conditions. Mechanism investigation revealed that •O₂^- and ¹O₂ were the vital reactive species for ARB inactivation and ARG degradation. The formation and transformation of the active species were proposed. Furthermore, the hierarchical macro-mesoporous structure of MM CS provided excellent optical and photoelectrochemical properties that promoted the cycle of Co³⁺/Co²⁺ and the effective utilization of PMS. This process was validated to be effective in various water matrices, including deionized water, underground water, source water, and secondary effluent wastewater. Collectively, this work demonstrated that the MM CS-based heterogeneous photo-Fenton-like process is a promising technology for controlling the spread of antibiotic resistance in aquatic environments.

Ultrafast degradation of contaminants in a trace cobalt(II) activated peroxymonosulfate process triggered through borate: Indispensable role of intermediate complex

Among all homogeneous catalysts, cobalt ions show the highest catalytic performance for the activation of peroxymonosulfate (PMS). Herein, we report a Co²⁺/PMS/H₃BO₃ system that can effectively generate reactive oxygen species (ROS) with ultra-low Co²⁺ dosage (5 μg/L). Co²⁺/PMS/H₃BO₃ system showed ultrafast reactivity and wide applicability for various pollutants. Sulfamethoxazole (SMX, 2 mg/L) could be completely removed within 5 min, and the corresponding k_obs reached up to 1.1239 min^-1. The introduction of H₃BO₃ significantly promoted the generation of ROS. The turnover frequency (TOF) calculated through dividing k_obs by the cobalt ions concentration is as high as 224.78 min^-1, which is much higher than most of the current research. Through a series of theoretical and experimental analyses, the complex of H₂BO₃^--MS (HSO₅B(OH)₃^-) was inferred to be the key substance that led to the excellent performance of the system. This work provides new insights into the Co²⁺/PMS system in the presence of borate buffer.

Activation of peroxymonosulfate by molybdenum disulfide-mediated traces of Fe(III) for sulfadiazine degradation

The activation of persulfate by ferrous iron (Fe(II)) is of great interest to the environmental remediation community, but the reduction of ferric iron (Fe(III)) to Fe(II) is slow and the accumulation of iron sludge resulted from the precipitation of Fe(III) is a great concern. Here, molybdenum disulfide (MoS₂) was studied as a co-catalyst to improve the activation of peroxymonosulfate (PMS) by Fe(III) for sulfadiazine (SDZ) degradation and different characterization technologies were used to reveal the reactive species. The results showed that a strong synergy existed between MoS₂ and Fe(III); approximately 94.3% of the SDZ was removed by MoS₂-Fe(III)-PMS after reaction for 30 min, while only 8.5% and 56.4% of the SDZ was removed by Fe(III)-PMS and MoS₂-PMS, respectively. Both hydroxyl radicals and sulfate radicals were generated and the latter was the primary species. In addition to the radicals, singlet oxygen was found to be generated and contributed to the degradation of SDZ. The chemical probe reaction with methyl phenyl sulfoxide showed that the generation of high-valent iron-oxo species was not obvious by MoS₂-Fe(III)-PMS under both acidic and neutral conditions. MoS₂ had good stability. No noticeable deactivation was observed during the 1st to 5th run and no obvious oxidation of surface Mo(IV) occurred. Based on the characterization of catalyst and oxidizing species, a mechanism for the activation of PMS by MoS₂-Fe(III) was proposed. The results from this study are expected to clarify the reactive species and deepen the understanding of MoS₂-promoted persulfate activation by Fe(II)/Fe(III).

Fabrication of Co3O4-Bi2O3-Ti catalytic membrane for efficient degradation of organic pollutants in water by peroxymonosulfate activation

In this study, a functionalized Co₃O₄-Bi₂O₃-Ti catalytic membrane (CBO-Ti-M) was prepared and applied for removing organic pollutants via activating peroxymonosulfate (PMS) in the dead-end filtration mode. Characterizations including scanning electron microcopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed that the Co₃O₄-Bi₂O₃ catalyst was successfully supported on the Ti membrane. The CBO-Ti-M /PMS system could efficiently remove various organic pollutants such as sulfamethoxazole, methyl orange, bisphenol A and methylene blue, achieving removal efficiencies of 98.0%-99.5%. The effects of PMS concentration, flow rate and solution environment on degradation efficiency were investigated in detail. Furthermore, quenching experiments, electron spin resonance (ESR) and in-situ open circuit potential (OCP) tests collectively demonstrated that singlet oxygen as well as the non-radical electron transfer pathway mainly contributed in the reaction mechanism. The synergistic effect of Co and Bi was illustrated according to XPS results, and the possible degradation pathway of MB was proposed based on LC-MS analysis. Reusability test showed that pollutant removal efficiency with the CBO-Ti-M /PMS system remained stable in four runs and limited metal leaching was observed.