Prussian Blue Analogue-derived co/fe bimetallic nanoparticles immobilized on S/N-doped carbon sheet as a magnetic heterogeneous catalyst for activating peroxymonosulfate in water

Self-Assembly Synthesis of Oxygen and Sulfur Co-Doped Porous Graphitic Carbon Nitride Nanosheets for Boosting CO2 Photoreduction

Graphitic carbon nitride (CN) has garnered considerable attention in the field of visible-light CO2 photoreduction, but its efficiency remains limited by the intrinsic π-conjugated skeleton. Here, O and S were co-doped CN (O, S/CN) by a facile "hydrolysis + calcination" approach to modulate the physicochemical and electronic structure. Distinctive from S doped CN (SCN), O, S/CN owned porous layer structure with several nanosheets and less SO4 2- groups on the surface. The amount of heteroatom-doping was achieved by changing the hydrothermal temperature. The optimum O, S/CN-80 achieved moderate CO production rate of 1.29 μmol g-1 h-1, which was 3.79 times as much as SCN (0.34 μmol g-1 h-1). The O and most S atoms were substitutionally doped and the effect of S doped state on the improved efficiency of CO generation in O, S/CN was also explored based on the theoretical calculations. This work provides an inspiration to develop efficient dual-doped CN photocatalysts for photocatalytic CO2 reduction.

A one-stone-two-birds strategy for cellulose dissolution, regeneration, and functionalization as a photocatalytic composite membrane for wastewater purification

Photocatalytic membranes integrate membrane separation and photocatalysis to deliver an efficient solution for water purification, while the top priority is to exploit simple, efficient, renewable, and low-cost photocatalytic membrane materials. We herein propose a facile one-stone-two-birds strategy to construct a multifunctional regenerated cellulose composite membrane decorated by Prussian blue analogue (ZnPBA) microspheres for wastewater purification. The hypotheses are that: 1) ZnCl2 not only serves as a cellulose solvent for tuning cellulose dissolution and regeneration, but also functions as a precursor for in-situ growth of spherical-like ZnPBA; 2) More homogeneous reactions including coordination and hydrogen bonding among Zn2+, [Fe(CN)6]3- and cellulose chains contribute to a rapid and uniform anchoring of ZnPBA microspheres on the regenerated cellulose fibrils (RCFs). Consequently, the resultant ZnPBA/RCM features a high loading of ZnPBA (65.3 wt%) and exhibits excellent treatment efficiency and reusability in terms of photocatalytic degradation of tetracycline (TC) (90.3 % removal efficiency and 54.3 % of mineralization), oil-water separation efficiency (>97.8 % for varying oils) and antibacterial performance (99.4 % for E. coli and 99.2 % for S. aureus). This work paves a simple and useful way for exploiting cellulose-based functional materials for efficient wastewater purification.

Surface reconstructed Fe@C1000 for enhanced Fenton-like catalysis: Sustainable ciprofloxacin degradation and toxicity reduction

The Fe-based catalysts typically undergo severe problems such as deactivation and Fe sludge emission during the peroxymonosulfate (PMS) activation, which commonly leads to poor operation and secondary pollution. Herein, an S-doped Fe-based catalyst with a core-shell structure (Fe@CT, T = 1000°C) was synthesized, which can solve the above issues via the dynamic surface evolution during the reaction process. Specifically, the Fe0 on the surface of Fe@C1000 could be consumed rapidly, leaving numerous pores; the Fe3C from the core would subsequently migrate to the surface of Fe@C1000, replenishing the consumed active Fe species. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses demonstrated that the reaction surface reconstructed during the PMS activation, which involved the FeIII in-situ reduction by S species as well as the depletion/replenishment of effective Fe species. The reconstructed Fe@C1000 achieved near-zero Fe sludge emission (from 0.59 to 0.08-0.23 mg L-1) during 5 cycles and enabled the dynamic evolution of dominant reactive oxygen species (ROS) from SO4·- to FeIVO, sustainably improving the oxidation capacity (80.0-92.5% in following four cycles) to ciprofloxacin (CIP) and reducing the toxicity of its intermediates. Additionally, the reconstructed Fe@C1000/PMS system exhibited robust resistance to complex water matrix. This study provides a theoretical guideline for exploring surface reconstruction on catalytic activity and broadens the application of Fe-based catalysts in the contaminants elimination.

Enhancing dye degradation using a novel cobalt metal-organic framework as a peroxymonosulfate activator

Among transition metals, cobalt ions exhibit superior catalytic activity in the peroxymonosulfate (PMS) degradation of pollutants. However, practical application is hindered by their high rate of ion leaching and the propensity for particle reunion issues. In this study, a novel cobalt metal-organic framework catalyst, denoted as CUST-565 ([Co3(BTB)2(BIPY)2]·4.5H2O·DMA), was synthesized via a one-step solvothermal method. The obtained crystal was employed as a catalyst to activate PMS for degrading two pollutants, methyl orange (MO) and rhodamine B (RhB), in wastewater. The catalyst demonstrated efficacy in PMS, achieving 97% degradation of MO and 98% degradation of RhB within 30 min at an initial concentration of 20.0 mg L-1. Additionally, various factors affecting dye degradation, including PMS dosage, catalyst dosage, temperature, initial pH, and coexisting anions, were investigated. Radical quenching experiments confirmed the presence of sulfate radicals (SO4˙-), hydroxyl radicals (HO˙), superoxide radicals (O2˙-), and singlet oxygen (1O2) in the system. After four cycles, CUST-565 retained its ability to catalytically degrade approximately 80% of the pollutants. These observed stability and reusability properties, corroborated by a series of characterization analyses before and after use, suggest that CUST-565 exhibits reliable performance. This work contributes to the development of cobalt-PMS catalysts for efficiently degrading dyes in wastewater.

Iron-Cobalt magnetic porous carbon beads activated peroxymonosulfate for enhanced degradation and Microbial inactivation

Magnetic carbon-based catalysts are promising materials for advanced oxidation processes, offering both high catalytic activity and environmental friendliness, and hold great potential in environmental remediation. In this work, Fe and Co zeolite imidazole frameworks (ZIFs) derived micron-sized magnetic porous carbon beads (MPCBs) were prepared by phase inversion and following the carbonization procedure, and the morphological and structural characteristics of the MPCBs were confirmed. The presence of pores and channels in the MPCBs provides a specific microenvironment for the for the catalysis of the core. Bisphenol A (BPA) was selected for the targeted pollutant, and the catalytic experiments confirmed that the effective catalytic activity of MPCBs in the presence of peroxymonosulfate (PMS), which could almost completely degrade BPA in 20 min with a reaction rate of 0.368 min-1. Furthermore, the MPCBs were used to effectively bacterial inactivation. Intermediate products of the BPA degradation process were validated and the toxicological studies showed a gradual decrease in toxicity, indicating effective reduction of potential hazards. The macroscopic preparation methods we developed for MPCBs that is promising for industrial applications and has the potential to cope with complex environmental remediation.

Visible-light-driven peroxymonosulfate activation by robust TiO2-base nanoparticles for efficient removal of sulfamethoxazole

In this study, a novel bimetallic Co-Mo-TiO2 nanomaterial was fabricated through a simple two-step method, and applied as photocatalyst to activate peroxymonosulfate (PMS) with high efficiency for sulfamethoxazole (SMX) removal under visible light. Nearly 100% of SMX was degraded within 30 min in Vis/Co-Mo-TiO2/PMS system, and its kinetic reaction rate constant (0.099 min-1) was 24.8 times higher compare with the Vis/TiO2/PMS system (0.014 min-1). Moreover, the quenching experiments and the electronic spin resonance analysis results confirmed that both 1O2 and SO4•- were the dominant active species in the optimal system, and the redox cycles of Co3+/Co2+ and Mo6+/Mo4+ promoted the generation of the radicals during the PMS activation process. Additionally, the Vis/Co-Mo-TiO2/PMS system exhibited a wide working pH range, superior catalytic performance toward different pollutants and excellent stability with 92.8% SMX removal capacity retention after three consecutive cycles. The result of density functional theory (DFT) suggested that Co-Mo-TiO2 exhibited a high affinity for PMS adsorption, as indicated by the length O-O bond from PMS and the Eads of the catalysts. Finally, the possible degradation pathway of SMX in optimal system was proposed through intermediate identification and DFT calculation, and a toxicity assessment of the by-products was also conducted.

Peroxymonosulfate activation by Fe-N-S co-doped tremella-like carbocatalyst for degradation of bisphenol A: Synergistic effect of pyridine N, Fe-Nx, thiophene S

Bisphenol A (BPA) has received increasing attention due to its long-term industrial application and persistence in environmental pollution. Iron-based carbon catalyst activation of peroxymonosulfate (PMS) shows a good prospect for effective elimination of recalcitrant contaminants in water. Herein, considering the problem about the leaching of iron ions and the optimization of heteroatoms doping, the iron, nitrogen and sulfur co-doped tremella-like carbon catalyst (Fe-NS@C) was rationally designed using very little iron, S-C₃N₄ and low-cost chitosan (CS) via the impregnation-calcination method. The as-prepared Fe-NS@C exhibited excellent performance for complete removal of BPA (20 mg/L) by activating PMS with the high kinetic constant (1.492 min^-1) in 15 min. Besides, the Fe-NS@C/PMS system not only possessed wide pH adaptation and high resistance to environmental interference, but also maintained an excellent degradation efficiency on different pollutants. Impressively, increased S-C₃N₄ doping amount modulated the contents of different N species in Fe-NS@C, and the catalytic activity of Fe-NS@C-1-x was visibly enhanced with increasing S-C₃N₄ contents, verifying pyridine N and Fe-N_x as main active sites in the system. Meanwhile, thiophene sulfur (C-S-C) as active sites played an auxiliary role. Furthermore, quenching experiment, EPR analysis and electrochemical test proved that surface-bound radicals (^·OH and SO₄^⋅-) and non-radical pathways worked in the BPA degradation (the former played a dominant role). Finally, possible BPA degradation route were proposed. This work provided a promising way to synthesize the novel Fe, N and S co-doping carbon catalyst for degrading organic pollutants with low metal leaching and high catalytic ability.

Efficient degradation of clothianidin and thiamethoxam in contaminated soil by peroxymonosulfate process

The widespread use of neonicotinoids has led to their frequent detection in the environment and potential environmental risk in recent years. Clothianidin (CLO) and thiamethoxam (TMX), as the second generation of neonicotinoid insecticides, are usually used as seed agents with a high risk of residue in the soil. Efficient degradation of CLO and TMX in soil using peroxymonosulfate (PMS) process was investigated in the present study. The degradation efficiencies of CLO and TMX reached 91.4% and 98.6% in 60 min with the addition of 20 mM PMS at pH 5.5 and 25℃. High degradation efficiencies of CLO were achieved with a high PMS dosage and temperature or a low CLO concentration and initial pH. The degradation of CLO was reduced in the presence of high concentration of inorganic anions (Cl^-, HCO₃^-). Soil organic matter might be one critical factor in the degradation of CLO and TMX. Radical scavenger experiments confirmed SO₄^•- and ¹O₂ were the dominant reactive species on the CLO and TMX degradation. Based on the detected degradation intermediates, the degradation pathways of CLO and TMX include dichlorination, hydroxylation, cleavage of C-N or C-C bond and further oxidation in the PMS-based soil. Overall, the PMS process is one effective and economical method for the remediation of the neonicotinoid contaminated soil.

Non-radical-dominated catalytic degradation of methylene blue by magnetic CoMoO4/CoFe2O4 composite peroxymonosulfate activators

In this study, magnetic CoMoO₄/CoFe₂O₄ (CMO/CFO) nanospheres with a core-shell structure were synthesized via two-step hydrothermal methods. The obtained particles were employed as catalysts to activate peroxymonosulfate (PMS) and degrade methylene blue (MB). The physico-chemical characterizations of the synthesized CMO/CFO showed that the CMO shell contributed to the enhancement of redox conversion and the increase in the concentration of oxygen vacancies (OVs). By examining reactive oxygen species (ROS) in the CMO/CFO/PMS system, the MB degradation was dominated by a non-radical pathway, and ¹O₂ was identified as the most abundant ROS. Besides, the CMO/CFO exhibited faster reaction kinetics than the pristine CFO. Moreover, the magnetic properties guaranteed the recycling and reuse of CMO/CFO, and the removal rate of MB was maintained at ∼94% after continuous use five times. Both the tolerance to SO₄^2-and the wide pH range where the material is applicable make it a promising catalyst for dyeing wastewater treatment.

Modulating Direct Growth of Copper Cobaltite Nanostructure on Copper Mesh as a Hierarchical Catalyst of Oxone Activation for Efficient Elimination of Azo Toxicant

As cobalt (Co) has been the most useful element for activating Oxone to generate SO4•-, this study aims to develop a hierarchical catalyst with nanoscale functionality and macroscale convenience by decorating nanoscale Co-based oxides on macroscale supports. Specifically, a facile protocol is proposed by utilizing Cu mesh itself as a Cu source for fabricating CuCo2O4 on Cu mesh. By changing the dosages of the Co precursor and carbamide, various nanostructures of CuCo2O4 grown on a Cu mesh can be afforded, including nanoscale needles, flowers, and sheets. Even though the Cu mesh itself can be also transformed to a Cu-Oxide mesh, the growth of CuCo2O4 on the Cu mesh significantly improves its physical, chemical, and electrochemical properties, making these CuCo2O4@Cu meshes much more superior catalysts for activating Oxone to degrade the Azo toxicant, Acid Red 27. More interestingly, the flower-like CuCo2O4@Cu mesh exhibits a higher specific surface area and more superior electrochemical performance, enabling the flower-like CuCo2O4@Cu mesh to show the highest catalytic activity for Oxone activation to degrade Acid Red 27. The flower-like CuCo2O4@Cu mesh also exhibits a much lower Ea of Acid Red 27 degradation than the reported catalysts. These results demonstrate that CuCo2O4@Cu meshes are advantageous heterogeneous catalysts for Oxone activation, and especially, the flower-like CuCo2O4@Cu mesh appears as the most effective CuCo2O4@Cu mesh to eliminate the toxic Acid Red 27.

Strategies for improving the catalytic activity of metal-organic frameworks and derivatives in SR-AOPs: Facing emerging environmental pollutants

As persulfate activator, Metal organic frameworks (MOFs) and derivatives are widely concerned in degradation of emerging environmental pollutants by advanced oxygen technology dominated by sulfate radical () (SR-AOPs). However, the poor stability and low catalytic efficiency limit the performance of MOFs, requiring multiple strategies to further enhance their catalytic activity. The aim of this paper is to improve the catalytic activity of MOFs and their derivatives by physical and chemical enhancement strategies. Physical enhancement strategies mainly refer to the activation strategies including thermal activation, microwave activation and photoactivation. However, the physical enhancement strategies need energy consumption and require high stability of MOFs. As a substitute, chemical enhancement strategies are more widely used and represented by optimization, modification, composites and derivatives. In addition, the identification of reactive oxygen species, active site and electron distribution are important for distinguishing radical and non-radical pathways. Finally, as a new wastewater treatment technology exploration of unknown areas in SR-AOPs could better promote the technology development.

Ultrafine cobalt nanoparticle-embedded leaf-like hollow N-doped carbon as an enhanced catalyst for activating monopersulfate to degrade phenol

While cobalt (Co) stands out as the most effective non-precious metal for activating monopersulfate (MPS) to degrade organic pollutants, Co nanoparticles (NPs) are easily aggregated, losing their activities. As many efforts have attempted to immobilize Co NPs on supports/substrates to minimize the aggregation issue, recently hollow-structured carbon-based materials (HSCMs) have been regarded as promising supports owing to their distinct physical and chemical properties. Herein, in this study, a special HSCM is developed by using a special type of ZIF (i.e., ZIF-L) as a precursor. Through one-step chemical etching with tannic acid (TA), the resultant product still remains leaf-like morphology of pristine ZIF-L but the inner part of this product becomes hollow, which is subsequently transformed to ultrafine Co-NP embedded hollow-structured N-doped carbon (CoHNC) via pyrolysis. Interestingly, CoHNC exhibits superior catalytic activities than CoNC (without hollow structure) and the commercial Co₃O₄ NPs for activating MPS to degrade phenol. The E_a value of phenol degradation by CoHNC + MPS was determined as 44.3 kJ/mol. Besides, CoHNC is also capable of effectively activating MPS to degrade phenol over multiple-cycles without any significant changes of catalytic activities, indicating that CoHNC is a promising heterogeneous catalyst for activating MPS to degrade organic pollutants in water.

Advances in the Application of Nanocatalysts in Photocatalytic Processes for the Treatment of Food Dyes: A Review

The use of food additives (such as dyes, which improve the appearance of the products) has become more prominent, due to the rapid population growth and the increase in demand for beverages and processed foods. The dyes are usually found in effluents that are discharged into the environment without previous treatment; this promotes mass contamination and alters the aquatic environment. In recent years, advanced oxidation processes (AOPs) have proven to be effective technologies used for wastewater treatment through the destruction of the total organic content of toxic contaminants, including food dyes. Studies have shown that the introduction of catalysts in AOPs improve treatment efficiency (i.e., complete decomposition without secondary contamination). The present review offers a quick reference for researchers, regarding the treatment of wastewater containing food dyes and the different types of AOPs, with different catalyst and nanocatalyst materials obtained from traditional and green chemical syntheses.

Bamboo-like N-doped carbon nanotube-confined cobalt as an efficient and robust catalyst for activating monopersulfate to degrade bisphenol A

As bisphenol A (BPA) is an extensively used chemical for manufacturing plastic products, discharge of BPA into the environment has caused serious threats to ecology. Therefore, -based chemical oxidation methods have been employed for eliminating BPA. Because monopersulfate (MNP) has become a popular reagent for obtaining , and Co is the most efficient metal for activating MNP, it is critical to develop heterogeneous Co catalysts for easier implementation and recovery. Herein, a unique Co-based catalyst is proposed by utilizing tubular-structured N-doped carbon substrates, derived dicyandiamide (DCDA), to confine Co nanoparticles (NPs). Through simple pyrolysis of a mixture of Co/DCDA, DCDA would be transformed into N-doped carbon nanotubes (CNT) to wrap the resultant Co NP, and, interestingly, this N-doped CNT would exhibit a special bamboo-like morphology. More importantly, as Co NPs are mono-dispersed and singly-confined in N-doped CNTs, forming CoCNT, CoCNT exhibits significantly higher catalytic activities than Co₃O₄, for activating MNP to degrade BPA. The enhancement of catalytic activities in CoCNT would be possibly ascribed to the synergistic effects between Co NP and the N-doped CNT which not only acts as the support/protection but also provides active sites. Therefore, CoCNT + MNP could lead to a much lower E_a (i.e., 13.8 kJ/mol) of BPA degradation than the reported E_a values. Besides, CoCNT is still effective for eliminating BPA even in the presence of high-concentration NaCl and surfactants. CoCNT is also reusable over many cycles and retains its catalytic activity with 100% BPA removal, demonstrating that CoCNT is an advantageous and robust catalyst for MNP activation.

Recent advances in cobalt-activated sulfate radical-based advanced oxidation processes for water remediation: A review

Sulfate radical-based advanced oxidation processes (SR-AOPs) have attracted increasing attention for the degradation of organic contaminants in water. The oxidants of SR-AOPs could be activated to generate different kinds of reactive oxygen species (ROS, e.g., hydroxyl radicals (OH), sulfate radicals (SO₄^-), singlet oxygen (¹O₂), and superoxide radicals (O₂^-)) by various catalysts. As one of the promising catalysts, cobalt-based catalysts have been extensively investigated in catalytic activity and stability during water remediation. This article mainly summarizes recent advances in preparation and applications of cobalt-based catalysts on peroxydisulfate (PDS)/peroxymonosulfate (PMS) activation since 2016. The review covers the development of homogeneous cobalt ions, cobalt oxides, supported cobalt composites, and cobalt-based mixed metal oxides for PDS/PMS activation, especially for the latest nanocomposites such as cobalt-based metal-organic frameworks and single-atom catalysts. This article also discussed the activation mechanisms and the influencing factors of different cobalt-based catalysts for activating PDS/PMS. Finally, the future perspectives on the challenges and applications of cobalt-based catalysts are presented at the end of this paper.

Efficient degradation of organic dye using Ni-MOF derived NiCo-LDH as peroxymonosulfate activator

Nickel-based metal-organic framework (Ni-MOF) was employed as a sacrificial template for the preparation of nickel-cobalt layered double hydroxide (NiCo-LDH) under different hydrolysis time. The template etching rate varied at different hydrolysis time, resulting in variations of the structural and morphology of NiCo-LDHs. The NiCo-LDH/10 sample showed a large specific surface area and the well-oriented larger dimension of thinner sheets due to the sufficient in-situ etching of the Ni-MOF template. The NiCo-LDH/10 was an excellent heterogeneous catalyst to activate peroxymonosulfate (PMS) for highly efficient Reactive Red-120 dye degradation. The results exhibited that the degradation efficiency of the NiCo-LDH/10-PMS catalyst was 89% for RR-120 dye within 10 min in the presence of the PMS system, which is higher than other NiCo-LDHs. Moreover, the other influencing factors such as PMS concentration, catalyst dosage, initial pH were also investigated towards degradation. The radical quenching measurement proved that the sulfate (SO₄^•-) and hydroxyl (OH^•) had been indicated as the primary radicals. Besides, the NiCo-LDH/10-PMS catalyst showed excellent reusability even after five consecutive cycles (83.6% of the degradation efficiency). This work offer insight study on the construction of controlled morphology NiCo-LDH heterogeneous structure for high-efficiency PMS activation.

Cobalt ferrite nanoparticle-loaded nitrogen-doped carbon sponge as a magnetic 3D heterogeneous catalyst for monopersulfate-based oxidation of salicylic acid

As salicylic acid (SAL) is increasingly consumed as a pharmaceutical product, release of SAL into the environment poses threats to ecology because of its low bio-degradability. Thus, SO₄^•--based chemical oxidation processes have been proposed for degrading SAL. Since monopersulfate (MPS) represents a primary reagent for generating SO₄^•-, and Co is the most capable metal for activating MPS to generate SO₄^•-, C₃O₄ NPs are frequently proposed for activating MPS but they are difficult to recover from water. Thus CoFe₂O₄ is considered as a magnetic alternative to Co₃O₄, and loading of CoFe₂O₄ NPs on substrates could further improve dispersion and avoid aggregation of NPs. Therefore, this study proposes a 3-Dimensional (3D) hierarchical catalyst which is fabricated by loading CoFe₂O₄ NPs on nitrogen-doped carbon sponge (NCS). The NCS is not only adopted as a support for CoFe₂O₄ NPs but also provides additional catalytic sites and enhances catalytic activities of CoFe₂O₄ NPs for MPS activation. As a result, CoFe₂O₄ NPs loaded on NCS (CFNCS) exhibits substantially higher catalytic activities than CoFe₂O₄ NPs and NCS individually with 100% of SAL could be afforded within 30 min. E_a of SAL degradation of 47.4 kJ/mol by CFNCS-activated MPS is also lower than those by other reported catalysts, whereas the RSE was 11.1%, which was also much higher than most of reported values. These features demonstrate that CFNCS is a promising 3D catalyst for enhancing MPS activation to degrade SAL. The findings obtained here are also insightful to develop efficient MPS-activating catalysts for eliminating contaminants.

Metal-complexed covalent organic frameworks derived N-doped carbon nanobubble-embedded cobalt nanoparticle as a magnetic and efficient catalyst for oxone activation

While Cobalt nanoparticles (Co NPs) are useful for catalytic Oxone activation, it is more advantageous to embed/immobilize Co NPs on nitrogen-doped carbon substrates to provide synergy for enhancing catalytic performance. Herein, this study proposes to fabricate such a composite by utilizing covalent organic frameworks (COF) as a precursor. Through complexation of COF with Co, a stable product of Co-complexed COF (Co-COF) can be synthesized. This Co-COF is further converted through pyrolysis to N-doped carbon in which cobaltic NPs are embedded. Owing to its well-defined structures of Co-COF, the pyrolysis process transforms COF into N-doped carbon with a bubble-like morphology. Such Co NP-embedded N-doped carbon nanobubbles (CoCNB) with pores, magnetism and Co, shall be a promising catalyst. Thus, CoCNB shows a much stronger catalytic activity than commercial Co₃O₄ NPs to activate Oxone to degrade toxic Amaranth dye (AMD). CoCNB-activated Oxone also achieves a significantly lower E_a value of AMD degradation (i.e., 27.9 kJ/mol) than reported E_a values in previous literatures. Besides, CoCNB is still effective for complete elimination of AMD in the presence of high-concentration NaCl and surfactants, and CoCNB is also reusable over five consecutive cycles.

Co3O4 nanocube-decorated nitrogen-doped carbon foam as an enhanced 3-dimensional hierarchical catalyst for activating Oxone to degrade sulfosalicylic acid

As sulfosalicylic acid (SUA) is extensively used as a pharmaceutical product, discharge of SUA into the environment becomes an emerging environmental issue because of its low bio-degradability. Thus, SO₄^--based advanced oxidation processes have been proposed for degrading SUA because of many advantages of SO₄^-. As Oxone represents a dominant reagent for producing SO₄^-, and Co is the most capable metal for activating Oxone to generate SO₄^-, it is critical to develop an effective but easy-to-use Co-based catalysts for Oxone activation to degrade SUA. Herein, a 3D hierarchical catalyst is specially created by decorating Co₃O₄ nanocubes (NCs) on macroscale nitrogen-doped carbon form (NCF). This Co₃O₄-decorated NCF (CONCF) is free-standing, macroscale and even squeezable to exhibit interesting and versatile features. More importantly, CONCF consists of Co₃O₄ NCs evenly distributed on NCF without aggregation. The NCF not only serves as a support for Co₃O₄ NCs but also offers additional active sites to synergistically enhance catalytic activities towards Oxone activation. Therefore, CONCF exhibits a higher catalytic activity than the conventional Co₃O₄ nanoparticles for activating Oxone to fully eliminate SUA in 30 min with a rate constant of 0.142 min^-1. CONCF exhibits a much lower Ea value of SUA degradation (35.2 kJ/mol) than reported values, and stable catalytic activities over multi-cyclic degradation of SUA. The mechanism of SUA degradation is also explored, and degradation intermediates of SUA degradation are identified to provide a possible pathway of SUA degradation. These features validate that CONCF is certainly a promising 3D hierarchical catalyst for enhanced Oxone activation to degrade SUA. The findings obtained here are also insightful to develop efficient heterogeneous Oxone-activating catalysts for eliminating emerging contaminants.

Development of 3-dimensional Co3O4 catalysts with various morphologies for activation of Oxone to degrade 5-sulfosalicylic acid in water

Since 5-sulfosalicylic acid (SFA) has been increasingly released to the environment, SO₄^--based oxidation processes using Oxone have been considered as useful methods to eliminate SFA. As Co₃O₄ has been a promising material for OX activation, the four 3D Co₃O₄ catalysts with distinct morphologies, including Co₃O₄-C (with cubes), Co₃O₄-P (with plates), Co₃O₄-N (with needles) and Co₃O₄-F (with floral structures), are fabricated for activating OX to degrade SFA. In particular, Co₃O₄-F not only exhibits the highest surface area but also possesses the abundant Co²⁺ and more reactive surface, making Co₃O₄-F the most advantageous 3D Co₃O₄ catalyst for OX activation to degrade SFA. The mechanism of SFA by this 3D Co₃O₄/OX is also investigated and the corresponding SFA degradation pathway has been elucidated. The catalytic activities of Co₃O₄ catalysts can be correlated to physical and chemical properties which were associated with particular morphologies to provide insights into design of 3D Co₃O₄-based catalysts for OX-based technology to degrade emerging contaminants, such as SFA.