Modulating the electron structure of Co-3d in Co3O4-x/WO2.72 for boosting peroxymonosulfate activation and degradation of sulfamerazine: Roles of high-valence W and rich oxygen vacancies

Pomelo peel biomass derived highly active advanced-oxidation-process catalyst: Complete elimination of organic pollutants

The advanced oxidation process (AOPs) is playing an important role in the elimination of hazardous organic pollutants, but the development of inexpensive and highly active advanced catalysts is facing challenges. In this study, a low-cost and readily available agricultural waste resource pomelo peel-flesh (PPF) biomass was used as the basic raw material, and the uniformly dispersed small cobalt nanoparticles were effectively anchored in the biochar derived from pomelo peel-flesh (BDPPF) by impregnation adsorption/complexation combined with heat treatment. Co/BDPPF (BDPPF embedded with Co) can effectively activate peroxymonosulfate (PMS) to SO4·-, ·OH and 1O2 reactive oxygen species, and achieve nearly 100% degradation of tetracycline persistent organic pollutant. Co/BDPPF can not only degrade tetracycline efficiently in complex water environment, but also degrade most organic pollutants universally, and has long-term stability, which solves the problem of poor universality and stability of heterogeneous catalysts to a certain extent. Importantly, Co/BDPPF derived from waste biomass was also innovatively designed as the core of an integrated continuous purification device to achieve continuous purification of organic wastewater. In this study, agricultural waste resources were selected as biomass raw materials to achieve efficient capture of Co2+, and finally developed advanced AOPs catalyst with excellent performance to achieve the purification of organic wastewater. It also provides a promising solution for the preparation of simple, low-cost, large-scale production of AOPs catalysts that can be put into actual production.

Fenton-like membrane reactor assembled by electron polarization and defect engineering modifying Co3O4 spinel for flow-through removal of organic contaminants

The application of Fenton-like membrane reactors for water purification offers a promising solution to overcome technical challenges associated with catalyst recovery, reaction efficiency, and mass transfer typically encountered in heterogeneous batch reaction modes. This study presents a dual-modification strategy encompassing electron polarization and defect engineering to synthesize Al-doped and oxygen vacancies (OV)-enriched Co3O4 spinel catalysts (ACO-OV). This modification empowered ACO-OV with exceptional performance in activating peroxymonosulfate (PMS) for the removal of organic contaminants. Moreover, the ACO-OV@polyethersulfone (PES) membrane/PMS system achieved organic contaminant removal through filtration (with a reaction kinetic constant of 0.085 ms-1), demonstrating outstanding resistance to environmental interference and high operational stability. Mechanistic investigations revealed that the exceptional catalytic performance of this Fenton-like membrane reactor stemmed from the enrichment of reactants, exposure of reactive sites, and enhanced mass transfer within the confined space, leading to a higher availability of reactive species. Theoretical calculations were conducted to validate the beneficial intrinsic effects of electron polarization, defect engineering, and the confined space within the membrane reactor on PMS activation and organic contaminant removal. Notably, the ACO-OV@PES membrane/PMS system not only mineralized the targeted organic contaminants but also effectively mitigated their potential environmental risks. Overall, this work underscores the significant potential of the dual-modification strategy in designing spinel catalysts and Fenton-like membrane reactors for efficient organic contaminant removal.

Sustainable and Rapid Water Purification at the Confined Hydrogel Interface

Emerging organic contaminants in water matrices have challenged ecosystems and human health safety. Persulfate-based advanced oxidation processes (PS-AOPs) have attracted much attention as they address potential water purification challenges. However, overcoming the mass transfer constraint and the catalyst's inherent site agglomeration in the heterogeneous system remains urgent. Herein, the abundant metal-anchored loading (≈6-8 g m-2) of alginate hydrogel membranes coupled with cross-flow mode as an efficient strategy for water purification applications is proposed. The organic flux of the confined hydrogel interfaces sharply enlarges with the reduction of the thickness of the boundary layer via the pressure field. The normalized property of the system displays a remarkable organic (sulfonamides) elimination rate of 4.87 × 104 mg min-1 mol-1. Furthermore, due to the fast reaction time (<1 min), cross-flow mode only reaches a meager energy cost (≈2.21 Wh m-3) under the pressure drive field. It is anticipated that this finding provides insight into the novel design with ultrafast organic removal performance and low techno-economic cost (i.e., energy operation cost, material, and reagent cost) for the field of water purification under various PS-AOPs challenging scenarios.

Constructing Hollow Multishelled Microreactors with a Nanoconfined Microenvironment for Ofloxacin Degradation through Peroxymonosulfate Activation: Evolution of High-Valence Cobalt-Oxo Species

This study constructed hollow multishelled microreactors with a nanoconfined microenvironment for degrading ofloxacin (OFX) through peroxymonosulfate (PMS) activation in Fenton-like advanced oxidation processes (AOPs), resulting in adequate contaminant mineralization. Among the microreactors, a triple-shelled Co-based hollow microsphere (TS-Co/HM) exhibited optimal performance; its OFX degradation rate was 0.598 min-1, which was higher than that of Co3O4 nanoparticles by 8.97-fold. The structural tuning of Co/HM promoted the formation of oxygen vacancies (VO), which then facilitated the evolution of high-valence cobalt-oxo (Co(IV)═O) and shifted the entire t2g orbital of the Co atom upward, promoting catalytic reactions. Co(IV)═O was identified using a phenylmethyl sulfoxide (PMSO) probe and in situ Raman spectroscopy, and theoretical calculations were conducted to identify the lower energy barrier for Co(IV)═O formation on the defect-rich catalyst. Furthermore, the TS-Co/HM catalyst exhibited remarkable stability in inorganic (Cl-, H2PO4-, and NO3-), organic (humic acid), real water samples (tap water, river water, and hospital water), and in a continuous flow system in a microreactor. The nanoconfined microenvironment could enrich reactants in the catalyst cavities, prolong the residence time of molecules, and increase the utilization efficiency of Co(IV)═O. This work describes an activation process involving Co(IV)═O for organic contaminants elimination. Our results may encourage the use of multishelled structures and inform the design of nanoconfined catalysts in AOPs.

Construction of cubic CaTiO3 perovskite modified by highly-dispersed cobalt for efficient catalytic degradation of psychoactive pharmaceuticals

Sulfate radical mediated advanced oxidation processes (SR-AOPs) have emerged as a promising alternative for emerging contaminants degradation. However, high activity and great stability are commonly difficult to juggle, and the structure-activity correlations are still ambiguous. This study constructed the cubic CaTiO3 perovskite modified by highly-dispersed cobalt for peroxymonosulfate (PMS) activation to improve the specific lattice plane exposure and reduce the metal leaching simultaneously. 98% of amitriptyline (AMT) degradation was achieved within 60 min under the condition of 200 mg/L Co0.1-CTO and 100 mg/L PMS. The results indicated that surface Co2+/Co3+ redox couple and lattice oxygen were responsible for PMS activation, and the evolution of ·OH, SO4·- and 1O2 were revealed. According to density functional theory (DFT) calculations, the highly-dispersed Co on cubic surface effectively captured PMS and promoted electron transfer for the generation of ·OH and SO4·-, while more oxygen atoms exposed on Co0.1-CTO(200) surface facilitated the generation of 1O2. Briefly, this study provides a novel strategy of catalyst synthesis in PMS activation for water treatment.

Activation of peroxymonosulfate with cobalt embedded in layered δ-MnO2 for degradation of dimethyl phthalate: Mechanisms, degradation pathway, and DFT calculation

The sulfate radical-based advanced oxidation processes (SR-AOPs) offer huge potential for the removal of organic pollutants. In this study, Co(II)-intercalated δ-MnO₂ (Co-δ-MnO₂) catalyst was successfully prepared by a simple cation exchange reaction. The obtained Co-δ-MnO₂ exhibited high catalytic performance for the removal of dimethyl phthalate (DMP) under the activation of peroxymonosulfate (PMS), with the degradation efficiency reaching 100% within 6 h. Experiments and theoretical calculations revealed that interlayer Co(II) provided unique active sites in Co-δ-MnO₂. In addition, radical and non-radical pathways were confirmed to play a role in Co-δ-MnO₂/PMS system. ^•OH, SO₄^{• ̶}, and ¹O₂ were identified to be the dominating reactive species in Co-δ-MnO₂/PMS system. This study provided new insights into the design of catalysts and laid a foundation for developing modifiable layered heterogeneous catalysts.

Role variations of MnOx on monoclinic BiVO4 (110)/(040) facets for enhanced Photo-Fenton reactions

Compared with traditional Fenton reaction, peroxymonosulfate based advanced oxidation processes (PMS-AOPs) are more effective to remove the organic pollutants in wastewater in a wider pH range. Herein, selective loading of MnO_x on monoclinic BiVO₄ (110) or (040) facets were achieved by photo-deposition method with addition of different Mn precursors and electron/hole trapping agents. MnO_x has good chemical catalysis activity for PMS activation, which can also enhance photogenerated charge separation, thus leading to enhanced activities than naked BiVO₄. The BPA degradation reaction rate constants of MnO_x(040)/BiVO₄ and MnO_x(110)/BiVO₄ system are 0.245 min^-1 and 0.116 min^-1, which are 6.45 and 3.05 times larger than that of naked BiVO₄, respectively. The roles of MnO_x on different facets are different, which will promote OER process on (110) facets and utilize the dissolved O₂ to produce O₂^•- and ¹O₂ more effectively on (040) facets. ¹O₂ is the dominated reactive oxidation species of MnO_x(040)/BiVO₄, while SO₄^•- and •OH play more important roles on MnO_x(110)/BiVO₄, which are proved by quenching experiments and chemical probe identifications, thus mechanism in MnO_x/BiVO₄-PMS-light system is proposed. The good degradation performance of MnO_x(110)/BiVO₄ and MnO_x(040)/BiVO₄ and mechanism theory may promote the application of photocatalysis in PMS based wastewater remediation.