The catalytic performance of biochar for peroxymonosulfate (PMS) activation strongly depends on its modification strategy, yet the relationship between structural regulation and activation mechanism remains insufficiently clarified. In this study, corn cob-derived biochar was synergistically modified using potassium oxalate activation and urea-assisted nitrogen doping to enhance surface defects and electronic properties for PMS activation toward phenol removal. The modified catalyst (K-NBC) exhibited a significantly increased specific surface area, approximately 36 times higher than that of pristine biochar. The effects of initial pH, PMS concentration, catalyst dosage, and phenol concentration were systematically evaluated. Radical quenching experiments, electron paramagnetic resonance (EPR), and electrochemical analyses suggested that free radicals, likely including O2•-, and non-radical electron-transfer pathways jointly contributed to phenol removal. Density functional theory (DFT) calculations and GC–MS/MS analysis were further employed to propose possible transformation pathways, and the ecotoxicity of detected intermediates was predicted using ECOSAR. This study provides insights into the rational design of defect-engineered and nitrogen-functionalized biochar catalysts for PMS-based advanced oxidation processes in water treatment.

Advanced oxidation processes employing natural carbonate minerals to activate peroxymonosulfate (PMS) have exhibited remarkable efficacy in the removal of organic pollutants. In this study, the differences in the degradation performance and mechanism of chloroquine phosphate (CQP) by calcite/PMS and dolomite/PMS systems were investigated. Experimental findings reveal that the calcite/PMS system demonstrates markedly superior removal under identical conditions, achieving 99 % CQP removal within 60 min. In contrast, the dolomite/PMS system only achieved 63 % CQP removal under the same conditions. Electron paramagnetic resonance (EPR) and radical quenching analyses identified singlet oxygen (1O2) as the dominant reactive species in both systems. Quantitative assessments indicated that the calcite/PMS system generated more 1O2 (43.3 mu M) compared to the dolomite/PMS system (35.4 mu M). This phenomenon was attributed to that calcite released more carbonate ions (CO32-) than dolomite. Although the two systems had different reaction rates, both achieved stable CQP removal over 90 % in a one-month continuous flow column experiments. This work developed the application potential of carbonate minerals in advanced oxidation systems. Furthermore, the findings contribute to better understanding and development of carbonate activated persulfate systems.

The microenvironment at the solid-liquid interface plays a pivotal role in activating peroxymonosulfate (PMS). This study quantitatively compared the alkaline microenvironments on calcite (Cal), aragonite (Ara), and vaterite (Vtr) surfaces, regarding their efficacy in activating PMS for Cu-EDTA decomplexation and Cu removal. Among these polymorphs, the Vtr/PMS system achieved the highest Cu-EDTA decomplexation (90.5 %) and Cu removal efficiency (84.6 %). Quenching tests, probe-based kinetic modeling and EPR experiments identified singlet oxygen (1O2) as the dominant reactive species across all systems, with the Vtr/PMS system generating the highest 1O2 exposure (1.21 x10- 8 M & sdot;s). Moreover, in-situ analysis of the interfacial microenvironment revealed that the Vtr/PMS system created a significantly more alkaline microenvironment (pH = 9.87), characterized by a rapid diffusion velocity of 34 mu m/s. This pronounced alkaline microenvironment exhibited a strong positive correlation with the accelerated production of 1O2, thereby promoting Cu-EDTA decomplexation. Furthermore, the Cu removal mechanism in the Vtr/PMS system involved a synergistic process combining adsorption, coprecipitation, and structural incorporation of Cu2+ during the transformation of Vtr into calcite. This work highlights the critical role of the alkaline microenvironment in carbonate mineral-based catalysis.

To further enhance the low-temperature water and sulphur resistance of samarium-modified hydrated sodium manganese ore, a composite morphology (alpha/S-MnO2) manganese oxide catalyst was synthesized via a two-step reduction process. Compared to the morphology of single S-MnO2, the two-step reduction method significantly improved multiple physicochemical properties, including specific surface area, chemisorbed oxygen content, and surface acidity, while also increasing the proportion of Mn3+. The catalytic performance of Ti0.05Sm0.05/Mn-TSM was evaluated via NH3-SCR testing, demonstrating 100% NO conversion and high N2 selectivity within the temperature window of 25-225 degrees C. Furthermore, the incorporation of titanium optimises the catalyst's electronic structure, markedly increasing the proportion of Mn3+. The maximum oxygen vacancy concentration replenishes the highly reactive oxygen species continuously depleted during the reaction, thereby enhancing resistance to water and sulphur contamination alongside post-poison recovery capability. In-situ DRIFT analysis at 50 degrees C suggests a dominance of the L-H mechanism for Sm0.05/Mn catalyst, whereas an E-R mechanism dominance over Ti0.05Sm0.05/Mn-TSM. This work demonstrates that the synergistic integration of alpha/S phase composite morphology and Ti doping not only delivers exceptional low-temperature activity and H2O/SO2 tolerance but also fundamentally alters the reaction pathway from a surface-limited L-H mechanism to a highly efficient E-R mechanism, providing a novel strategy for designing next-generation SCR catalysts.

Advanced Oxidation Processes (AOPs) represent an effective approach for treating heavy metal complexes (HMCs) wastewater, but the impact of coexisting metal ions on these processes remains inadequately understood. This study systematically investigated the impact of Fe3+, Fe2+, Mn2+, Cu2+, Ni2+, and Zn2+ on Cu(II)-EDTA decomplexation and Cu removal within the Calcite/PMS system. Among tested metal ions, 0.1 mg/L Fe3+ significantly promoted Cu(II)-EDTA decomplexation, achieving the highest Cu(II)-EDTA decomplexation rate (0.433 min-1) and Cu removal efficiency (83.54 %). Trace Fe3+ enhanced Cu(II)-EDTA decomplexation via accelerating singlet oxygen (1O2) generation. The underline mechanism involves Fe3+ hydrolysis in calcite-buffered alkaline environment, leading to the in-situ formation of active surface iron hydroxyl (Fe-OH) as PMS activation sites. The Fe-OH reshapes the calcite surface electronic structure, lowering PMS adsorption energy, and enabling efficient d-p orbital electron transfer. This facilitates O-O bond cleavage, reduces the Gibbs free energy barrier and accelerates 1O2 generation. Moreover, the Calcite/Fe3+/PMS system showed exceptionally stable treatment performance in 30-day continuous flow experiments. This work highlights trace Fe3+ as an efficient catalytic enhancer in alkaline AOPs, offering a sustainable strategy for HMCs wastewater remediation.

The efficient degradation of SAs is a significant challenge for the treatment of wastewater. To address this, the Fe1-xS@BC was prepared by calcining a mixture of pyrite and biomass, and used to activate peroxydisulfate (PDS) to degrade sulfadiazine (SDZ). The effect of carbon sources (wheat straw, rice husk, and corn cob) on catalytic activity of Fe1-xS@BC were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), total Fe dissolution and free radical quantification. The results indicate that Fe1-xS@WBC with carbon defects and oxygenated functional groups facilitate the dissolution of Fe and the generation of ·OH and ·SO4-. Additionally, the electron-rich the thiophene S facilitate the regeneration of Fe(II). In the Fe1-xS@WBC/PDS system, 90.3% of SDZ degradation could be achieved under optimal conditions: Fe1-xS@WBC = 0.5 g L-1, SDZ = 10 mg L-1, PDS = 2.0 mM, initial solution pH = 7.0. In addition, Fe1-xS@WBC/PDS system exhibits strong resistance to interference from Cl-, and NO3-, while elevated concentrations of HCO3-, HPO42-, and HA hinder SDZ degradation. The Fe1-xS@WBC/PDS system shows excellent selectivity and recoverability. Quenching experiments and electron spin resonance (ESR) reveal the involvement of ·OH, ·SO4-, and 1O2 in the degradation of SDZ within Fe1-xS@WBC/PDS system. Furthermore, four possible degradation pathways for SDZ were proposed based on density functional theory (DFT) and liquid chromatography-mass spectrometry (LC-MS) analysis, while assessing the toxicity of degradation intermediates. This study not only introduces a novel catalytic system for the efficient degradation of antibiotic-contaminated wastewater, but also provides a theoretical foundation for the development and application of iron sulfide-biomass composite catalysts.

Birnessite-type (δ-MnO2) exhibits a high adsorption and catalytic performance to remove organic contaminants, but it still suffers from agglomerates, low specific surface area, and uneven distribution of active sites. Here, a novel birnessite-loaded biochar (δ-MnO2@BC, MBC) was prepared by chemical precipitation and used for the catalytic degradation of tetracycline under visible light. The biochar provides a large number of birnessite loading sites, which increases the specific surface area of the material, and reduces the electron–hole pair complexation rate. Photocatalytic results showed that under optimal conditions, 91.89

Defect strategy is one of the most effective approaches for enhancing the efficiency of Mn-based catalysts in removing formaldehyde (HCHO) under ambient conditions. Herein, the interlayer Mn-O octahedra in birnessite synergistically form with Mn vacancies through proton exchange in acidic solutions, creating surface Frenkel defects. As evidenced by highly combined physicochemical characterization and density functional theory calculations, surface Frenkel defects are highly active sites on the surface of birnessite. The surface Frenkel defects can induce surface electronic reconstruction, generating strong electrophilicity, which promotes the evolution of superoxide radicals (O-2(center dot-)) into singlet oxygen (O-1(2)). In-situ quenching DRIFTS indicates that O-1(2) is the most important ROS in the oxidation process of HCHO. Additionally, the surface Frenkel defects enhance the adsorption of HCHO, promoting the dehydrogenation of HCHO to form CO, which is then rapidly oxidized to CO2 and H2O under the action of O-1(2). This provide a more effective kinetic and thermodynamic catalytic pathway. The defect-rich birnessite (R-Bir) achieved complete HCHO removal in the dynamic test at 10 ppm within 10 hours, significantly outperforming defect-free birnessite (F-Bir) and most previously reported catalysts. This study precisely reveals the catalytic mechanism of HCHO over R-Bir and provides valuable insights for the design of high-performance environmental catalysts.

Effective removal of heavy metal complexes from contaminated water remains a challenging task. In this work, a limestone/PMS system was constructed for the efficient degradation of Cu-EDTA. Under the conditions of 3.0 g/L limestone and 1.0 mM PMS, the degradation efficiency of 10.0 mg/L Cu-EDTA reached 99.0 % in 60 min, and the removal efficiency of Cu ions approached 50.0 %. The main active specie revealed by quenching and EPR experiments was the singlet oxygen (1O2). Interestingly, Trace amounts of Cu(II) in limestone react with PMS enhancing the degradation of Cu-EDTA. The results of the HPLC-MS analysis showed that the reactive species attacked the Cu-O and Cu-N bonds, as well as triggered a decarboxylation process, resulting in the decomposition of Cu-EDTA into six intermediates. Meanwhile, SEM and XPS analyses revealed that Cu ions released during the degradation of Cu-EDTA are deposited on the limestone surface as Cu(OH)2 and Cu2(OH)2CO3. In addition, the initial pH and co-existing ions have a weak effect on the system. Finally, a one-month continuous flow experiment showed that the degradation efficiency of Cu-EDTA was about 95.0 % and the removal efficiency of Cu ions was 40.0 %. In conclusion, this study provides a new approach for the destruction of metal complexes and the removal of heavy metals.

The bimetallic synergistic effect plays a significant role in enhancing the efficiency of antibiotics degradation via hydrogen peroxide (H2O2) activation. In this study, the degradation of sulfamethazine sodium (SMT) by H2O2 was comprehensively explored in a system where Cu(II) and Co(II) ions synergistically activate H2O2 in the presence of calcite. The Cu(II)/Co(II)/calcite/H2O2 system using only 1.0 mg/L of Cu(II), exhibits excellent oxidation capacity, enabling complete removal of SMT within 1 h (0.085 min-1). This rate is 4.5 and 23.5 times higher than those observed in the Cu(II)/calcite/H2O2 (0.019 min-1) and Co(II)/calcite/H2O2 systems (0.0036 min-1), respectively. According to scavenger experiments, ESR captures test, and chemical probe experiments, it is determined that Cu(III) primarily contributes to SMT degradation, rather than hydroxyl radicals (center dot OH), singlet oxygen (1O2), and high valent cobalt-oxo species [e.g. Co(IV)]. The introduction of Co(II) promotes the formation of Cu(III) by accelerating the oxidation of Cu(II). Furthermore, the degradation pathways for SMT are elucidated through UPLC-ESI-MS/MS analysis, and variations in toxicity are rigorously assessed using the ECOSAR program. In summary, this study reveals the highly effective synergistic activation of H2O2 by Cu(II) and Co(II) in the presence of calcite, offering new insights into the comprehensive utilization of calcite in environmental catalysis, particularly for addressing the pollution caused by coexisting heavy metals and antibiotics.

Marine biofouling is a global challenge that severely compromises the service life of marine equipment, significantly increasing maintenance costs and causing substantial ecological damage. In this work, inspired by natural antifouling mechanisms, a bioinspired hydrophilic nanostructured poly(ether ether ketone) (PEEK) surface with fluorescence antifouling functionality was developed, producing a novel, efficient, broad-spectrum, and environmentally friendly antifouling mode. The bioinspired surface featured cicada-wing-inspired nanostructures on its top, which exerted mechanical bactericidal effects. Subsequently, a facile and stable nanoscale polyphenol network (NPN) layer was designed to encapsulate zwitterionic polymers and fluorescent response agents through simple one-step self-assembly anchoring on the nanostructure. The resultant antifouling PEEK surface exhibited excellent resistance against the adhesion of proteins, bacteria, and algae while simultaneously demonstrating high efficacy in the killing of adhered microorganisms. This novel fluorescent bioinspired hydrophilic nanostructured PEEK surface offers a new strategy for the development of marine, industrial, and biomedical equipment.

Antibiotics are widely used in both pharmaceutical and aquaculture industries, but due to their poor biodegradability, their accumulation in the environment continues to climb, leading to a serious antibiotic pollution problem. In view of this, in this paper, an efficient and environmentally friendly p-n heterojunction photocatalytic material was successfully synthesized with CuBi2O4 using MIL-101 (Fe) as a framework for the degradation of tetracycline antibiotics, which provides a new way to solve the problem of antibiotic pollution. Through a solvothermal method, MIL-101(Fe)/CuBi2O4 photocatalytic composite materials in different ratios were successfully prepared. Then these materials were characterized by XRD, SEM, XPS, UV-vis DRS, and BET techniques. The results of the tetracycline degradation experiments showed that the degradation efficiency of this MIL-101(Fe)/CuBi2O4-0.8 composite was as high as 98.66 % and 87.12 % for the tetracycline solutions of 20 mg/ L and 40 mg/L, after 1 h of light exposure. Analysis of the first-order kinetic curves revealed that the degradation rates of the composite material for tetracycline solutions of different concentrations were 2.8 times and 1.8 times that of the MIL-101(Fe) monomer. Finally, the flat-band potentials of MIL-101(Fe) and CuBi2O4 were determined using an electrochemical workstation, and their valence band and conduction band values were calculated. Based on the above relevant theories and data, the possible electron transfer mechanism and catalytic mechanism of MIL-101(Fe)/ CuBi2O4 photocatalytic composites were proposed.

This study showcases the performance of Fe3O4 (S600) derived from the decomposition of siderite in activating peroxymonosulfate (PMS) for the 2,4-dichlorophenol (2,4-DCP) degradation, as well as the enhancement of visible light in the S600/PMS system. With the involvement of visible light, 2 g/L Fe3O4 and 0.5 mM PMS achieved 100 % degradation of 2,4-DCP within 70 min. Singlet oxygen (1O2) and hydroxyl radicals (center dot OH) were the primary reactive species responsible for 2,4-DCP degradation under visible light irradiation based on the scavenging experiments and electron paramagnetic resonance (EPR) analysis. Importantly, compared to the absence of visible light, the visible light boosted 1O2 production and accelerated 2,4-DCP degradation. The effects of various operating parameters on the degradation efficiency were also examined, and the intermediates and possible degradation pathways of 2,4-DCP were identified. This study proves that the integrated utilization of natural siderite derivatives to activate oxidants for pollutant degradation is a promising approach.

Despite the great potential of sulfur -based autotrophic denitrification, an improvement in nitrate removal rate is still needed. This study used the desulfurized products of Mn ore to develop the MnS-S 0 -limestone autotrophic denitrification system (MSLAD). The feasibility of MSLAD for denitrification was explored and the possible mechanism was proposed. The nitrate (100 mg/L) was almost removed within 24 h in batch experiment in MSLAD. Also, an average TN removal of 98 % (472.0 mg/L/d) at hydraulic retention time of 1.5 h in column experiment (30 mg/L) was achieved. MnS and S 0 could act as coupled electron donors and show synergistic effects for nitrate removal. gamma-MnS with smaller particle size and lower crystallinity was more readily utilized by the bacterium and had higher nitrate removal efficiency than that of alpha-MnS. Thiobacillus and Sulfurimonas were the core functional bacterium in denitrification. Therefore, MnS-S 0 -limestone bio-denitrification provides an efficient alternative method for nitrate removal in wastewater.

Magnetic Fe1-xS@SC nanorods were synthesized by sulfurizing MIL-88A (Fe) and utilized to activate peroxydisulfate (PDS) for the degradation of tetracycline (TC). The superior catalytic performance of Fe1-xS@SC can be attributed to its close contact interface, high electron density, and excellent electron transfer conductivity. Both radical pathway ((center dot) SO4-, (OH)-O-center dot, O-center dot(2)-) and nonradical pathway (O-1(2)) were found to be responsible for the degradation of TC in Fe1-xS@SC/PDS system, with the electron transfer played a crucial role. Importantly, a high linear correlation (R-2 = 0.9153) between the level of carbon defect and the reaction rate constant confirmed the structure-activity relationship between graphitization and catalytic activity. The Fe1-xS@SC/PDS system has the advantages of strong anti-interference ability (Cl-, NO3-, HA), broad applicability, recyclability, and low PDS consumption. Furthermore, possible degradation pathways of TC were proposed and the toxicity of intermediates was evaluated. This study provides novel insight into carbon materials and iron sulfide to purify antibiotic-contaminated wastewater by activating PDS

Manganese oxides prove to be a promising catalyst for formaldehyde (HCHO) elimination in catalytic oxidation. In this study, MnO2 with different crystalline structure (α-MnO2, ²-MnO2, γ-MnO2, and δ-MnO2) were synthesized by hydrothermal method to investigate their catalytic performances towards the abatement of formaldehyde. The prepared catalysts were characterized and analyzed by the X-ray diffraction (XRD), hydrogen-temperature programmed reduction (H2-TPR), BET specific surface area, X-ray photoelectron spectroscopy (XPS), and ammonia-temperature programmed desorption (NH3-TPD). In addition, the apparent activation energy was also calculated by using Arrhenius plots. Among the above four prepared catalysts, the γ-MnO2 has the best destruction and removal efficiency (DRE), which was approaching to 100

In order to find efficient catalysts for low-temperature selective catalytic reduction with ammonia (NH3-SCR), several MnO2 with different crystal structure have been supported on high-purity palygorskite (Pal) by a hydrothermal method. The effect of MnO2 crystal structures on the NH3-SCR performance of the catalysts was investigated. All catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, Raman spectrum, Thermo gravimetric analysis/Differential thermo gravimetric (TG/DTG), ammonia-temperature programmed desorption (NH3-TPD), hydrogen-temperature programmed reduction (H2-TPR), Transmission electron microscope (TEM) and X-ray energy dispersive spectroscopy (EDS) and X-ray photoelectron spectrometer (XPS). The presented results suggested that α-MnO2/Pal catalyst exhibit the highest catalytic activity among four type MnO2/Pal catalysts in the temperature range of 50–400°C, own promising stability during a 24 h continuous denitration experiment. Furthermore, the crystal structure affords α-MnO2/Pal with the highest specific surface area and more acidic sites, which is beneficial for the SCR reaction. It has improved the NH3 adsorption ability and catalytic activity of the catalyst.

To develop novel NH3-SCR catalysts with low-temperature and high-efficency, a series of birnessite (6-MnO2) catalysts with different Sm doping by methanol reduction are synthesized. The results showed that the introduction of Sm successfully inhibited the crystallization of MnOX, promoted the specific surface area, the contents of chemisorbed oxygen species and the formation of surface acid sites. It also increased the relative content of (Mn4+ + Mn3+)/Mn, which was beneficial to low-temperature SCR activity. The catalytic performance of xSm/ Mn (6-MnO2 based with xSm doping) catalysts was evaluated by NH3-SCR performances. Among them, 0.05 Sm/ Mn showed 100% NOX conversion and high N2 selectivity compared to the other Sm addition catalysts within the operating low-temperature window (25-200 degrees C), at a high GHSV (gas hourly space velocity) of 60,000 h-1. The modified 0.05 Sm/Mn catalysts followed the L-H and E-R reaction mechanisms and were dominated by L-H, as revealed by in-situ DRIFTs analysis.

The NO conversion by Fe-substituted rhodochrosite before flue gas treatment systems in coaling plants needs further investigation. Hence the effect of Fe substitution on the conversion of rhodochrosite during coal combustion process conditions and the denitration efficiency of transformed products after NH3 injection were investigated. To simulate the reality of coaling process, Fe-substituted manganese oxide was obtained by instant heat treatment of Fe-substituted rhodochrosite. The manganese oxide obtained from the instant-calcined rhodochrosite had promising catalytic activity, the substitution of Fe slightly enhanced NO conversion efficiency at 100-200 degrees C and 3 %Fe-850 exhibited the maximum NO conversion of 99.6 % at 150 degrees C. Besides, the Fe doping enabled the thermal decomposition product of rhodochrosite to have higher porosity, lager surface area, more chemisorbed oxygen and acid sites, better redox capacity and greater relative content of Mn4+. Furthermore, in-situ DRIFTs experiment demonstrated Fe doping increased the number of acid site and promoted the formation of intermediates (-NH2) and monodentate nitrite, which will benefit catalytic activity. Moreover, E-R mechanism was dominant in the reaction at different temperatures. This work improves our understanding of the de-NOx behavior following NH3 injection during coaling.

The high concentration of ammonia nitrogen (NH4+) and chemical oxygen demand (COD) in biogas slurry pose great challenge to the efficiency of traditional wastewater treatment systems. Collophanite tailings are solid waste, characterized by significant concentrations of phosphorus (PO43-) and magnesium (Mg2+), represent a potential resource for the reduction and recovery of NH4+ in biogas slurry via struvite precipitation. This study systematically explored the optimal leaching parameters employing sulfuric acid for the extraction of PO43- and Mg2+ from collophanite tailings. The effect of [PO43-]:[NH4+] molar ratio and pH on the recovery of NH4+ in biogas slurry was investigated. The physicochemical properties of the precipitates were confirmed using X-ray diffraction (XRD), SEM (scanning electron microscopy), and chemical analysis. Results suggested that the highest removal efficiency of NH4+ (88.5%) was achieved when employing a [PO43-]:[NH4+] molar ratio of 1.0 at pH 9.5. Evaluation of effluent quality demonstrate a significant enhancement in the biodegradability of the treated biogas slurry, evidenced by an increase in the COD/TN ratio increased from 2.1 to 10.4. Economic analysis shows that the net income would be approximately 21.33 USD/m(3) for proposed produces. These findings underscore the potential of utilizing collophanite tailings for NH4+ recovery from biogas slurry.