Activation of periodate by N-doped iron-based porous carbon for degradation of sulfisoxazole: Significance of catalyst-mediated electron transfer mechanism

Electrical activation of periodate by nano-zero-valent cobalt/nitrogen-doped carbon for sulfisoxazole degradation: Insights into rapid electron transfer mechanisms

Periodate (PI) activation via three-dimensional electrochemical (E) is a promising approach for degrading sulfisoxazole (SIZ), while the scarcity of active sites significantly limits the efficient electron-transfer rate. Herein, we synthesized multiple strongly active zero-valent cobalt (Co0) nanoparticles encapsulated in nitrogen-doped carbon (NC) shells through Co-potassium chloride (KCl) doping pyrolysis of Zeolitic Imidazolate Framework-8 (ZIF-8) to induce the rapid electron transfer pathways (ETP). Specifically, molten KCl doping provides confined structures for Co0 with a diameter of 12.57 nm embedded in the NC shell, thereby expanding the active space of Co0/NC. The generated Co0/NC exhibited an enormous electrochemically active surface area (ECSA, 736.92 cm2/mg), low charge transfer resistance (Rct, 38.50 Ω), and strong adsorption energy (-6.003 eV), which together promote robust electron transfer kinetics. Capitalizing on these properties, the E-Co0/NC-PI system achieved 100% SIZ removal at a degradation rate of 1.587 min-1 under near-neutral (pH 5.00-9.00) conditions, with ultra-low energy consumption (0.011 kWh m-3, $0.125/L). This study highlights a Co0/NC-induced rapid ETP for SIZ removal, offering insights into enhanced electrical activation of PI for wastewater treatment.

Periodate activation by plasma coupled with FeNC for contaminant removal: Machine learning assisted catalyst optimization and electron shuttle mechanism

Emerging contaminants (ECs) pose great challenges to water treatment technology due to their complexity and high harm. In this paper, the method of dielectric barrier discharge (DBD) plasma coupled with iron-based catalyst (FeNC) activating periodate (PI) was first designed for ECs removal. The ingenious introduction of FeNC not only promotes the Fenton-like reaction of DBD system but also reduces the PI activation energy barrier and accelerates the electron shuttle between PI and pollutants. Based on the parameters evaluation of machine learning (ML), the calcination temperature of 575 ℃ and 17 % N addition were determined for best catalytic performance. XRD, Raman spectroscopy, XPS and density functional theory (DFT) analysis show that optimized catalyst has better electron shuttle characteristics and PI activation ability. Compared to DBD (78 %) and DBD/PI (94 %), DBD/FeNC/PI could achieve 100 % degradation efficiency of sulfadiazine (SDZ) in 12 min with high reaction rate. In addition to the effects of ROSs (1O2, OH and O2-), the efficient electron transfer mediated by FeNC and PI is the key to promoting the degradation of pollutants. The progressive dissociation of pyrimidine ring under the action of OH and electron transfer is the main pathway of SDZ degradation. The toxicity of intermediate products produced by the system is generally lower than that of SDZ. The system still has a high SDZ removal efficiency in actual water and has a good removal effect for other types of ECs, which also makes the system have a better practical prospect.

Applications of periodate activation for emerging contaminants treatment in water: Activation methods, reaction parameters and mechanism

Emerging contaminants pose a serious hazard to the water environment and human health due to their difficult degradation. In recent years, periodate-based oxidation processes have aroused tremendous attention in environment remediation due to their high oxidative potential for the degradation of contaminants and fair stability in the water. Periodate activation methods (i.e., thermal activation, photoactivation, microwave and ultrasonic activation, metal catalyst activation, carbon activation, H2O2 activation and electrochemical activation) were revealed. The generation mechanisms of the main reactive species in the periodate-based advanced oxidation processes were discussed. The degradation mechanisms of periodate-based systems are classified into two categories: radical-based mechanisms (the generation and mutual transformation of reactive radicals (IO3•, •OH, IO4• and O2•-)) and non-radical mechanisms (mainly including electron transfer and 1O2). The IO3• is a common reaction product along with the applications of periodate oxidation. The factors affecting periodate activation have been summarized and the characteristics of various activation methods have been compared. The combination of periodate oxidation with effective methods of activation has been expected to significantly enhance the treatment of organic contaminants in wastewater. This review systematically summarized the various methods for periodate activation and the research progress of its application in water treatment in recent years.

N-coordinated iron sites dispersed in porous carbon frameworks to activate peroxymonosulfate for efficient sulfisoxazole degradation and real hospital wastewater decontamination

Herein, an N-coordinated Fe site dispersed in porous carbon frameworks (Fe-NC) fabricated from zeolitic imidazolate frameworks encapsulated with iron acetylacetonate (Fe(acac)3 @ZIFs) was employed to activate peroxymonosulfate (PMS) for the attenuation of sulfisoxazole (SIZ) and treating real hospital wastewater. The constructed Fe-NC/PMS system exhibited good catalytic stability for SIZ degradation, maintaining excellent degradation performance over multiple cycles with virtually no leaching. The quenching experiments, electron paramagnetic resonance (EPR) capture analyses, and semi-quantitative measurements showed that singlet oxygen (1O2) and high-valent metal-oxo species were mainly responsible for SIZ degradation by Fe-NC/PMS. Significantly, ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS/MS) was used to trace 134 pharmaceutical contaminants in real hospital wastewater. Effective degradation was achieved for 87 % of the pharmaceutical contaminants by the Fe-NC/PMS process. Seventy-four pharmaceutical contaminants were eliminated. Taken together, this work successfully established the Fe-NC/PMS technology using the developed iron-based materials and explored its application to real hospital wastewater treatment, providing an eco-friendly and effective strategy for treating wastewater.

Nitrogen and magnesium codoped biochar activates periodate to remediate bensulfuron methyl-contaminated water at low temperature: Performance, mechanisms, and phytotoxicity

Bensulfuron methyl (BSM), a typical sulfonylurea herbicide, has been widely used worldwide for weed suppression and crop protection. Nevertheless, the long-term and prolonged usage led to residues in environment, resulting in the reduction of crop yields and even threatening food security. In this study, the nitrogen/magnesium codoped biochar (NMg-BC) was prepared via two-step pyrolysis method to activate periodate (PI) for BSM degradation. The results demonstrated BSM degradation rate was 87.9 % within 10 min by NMg-BC/PI system at 15 ℃. The system exhibited the favorable tolerance to environmental changes (pH, temperature, anions, and humic acids), presenting high removal efficiency of BSM. Radicals (IO3•) and non-radicals (1O2 and electron transfer) pathways contributed to the degradation of BSM, while the latter performed a crucial role in BSM degradation. Theoretical calculations further confirmed doped of N and Mg changed the electron configuration and electrostatic potential (ESP) distribution of biochar, which was beneficial to provide more active sites for PI activation. Hydroponic experiments showed that NMg-BC/PI system could effectively degrade BSM, and its residue had no significant effect on the length and weight of soybean. The study provides a promising approach for the pollutant remediation in cold regions.

Mechanism insights into metal-organic framework-derived carbon materials activating periodate for p-chlorophenol removal: The role of S and Fe co-doping

Periodate (PI, IO4-)-based advanced oxidation processes (AOPs) provide an economical and sustainable approach to alleviate water pollution challenges. Developing efficient and stable activators for PI is the focus of current research. Herein, S/Fe-co-doped magnetic porous carbon material (S/Fe-ZIF-950) was prepared by introducing exogenous S atoms using Fe-doped zeolitic imidazolate framework-8 (Fe-ZIF-8) as a precursor, which showed the most superior performance (100 % within 10 min) in activating PI to remove p-chlorophenol (4-CP). Quenching tests, electron spin resonance and electrochemical characterizations revealed that IO3·, 1O2, ·O2- dominated the 4-CP degradation process with Fe3C and ZnS as the main active sites. The synergistic effect of S and Fe was the main reason for the enhanced degradation performance of 4-CP in S/Fe-ZIF-950/PI system, among which the reducing S2- could effectively promote the regeneration of Fe(Ⅱ), thus facilitating the continuous generation of active species. Combined with LC-MS results and density functional theory (DFT) calculations, possible degradation routes of 4-CP in the S/Fe-ZIF-950/PI system were presented. Moreover, toxicity assessment showed that the S/Fe-ZIF-950/PI system exhibited low biotoxicity and no toxic iodine by-products were formed. In addition, S/Fe-ZIF-950/PI system demonstrated excellent activity, good stability, outstanding reusability and durability in a variety of complex water environments. This study investigated the activation mechanism of S/Fe-co-doped porous carbon materials on PI, which shed a new light on the catalytic activation of PI by heteroatom-doped Fe-loaded carbon-based materials.

Electron transfer mediated activation of periodate by contaminants to generate 1O2 by charge-confined single-atom catalyst

The electron transfer process (ETP) is able to avoid the redox cycling of catalysts by capturing electrons from contaminants directly. However, the ETP usually leads to the formation of oligomers and the reduction of oxidants to anions. Herein, the charge-confined Fe single-atom catalyst (Fe/SCN) with Fe-N3S1 configuration was designed to achieve ETP-mediated contaminant activation of the oxidant by limiting the number of electrons gained by the oxidant to generate 1O2. The Fe/SCN-activate periodate (PI) system shows excellent contaminant degradation performance due to the combination of ETP and 1O2. Experiments and DFT calculations show that the Fe/SCN-PI* complex with strong oxidizing ability triggers the ETP, while the charge-confined effect allows the single-electronic activation of PI to generate 1O2. In the Fe/SCN + PI system, the 100% selectivity dechlorination of ETP and the ring-opening of 1O2 avoid the generation of oligomers and realize the transformation of large-molecule contaminants into small-molecule biodegradable products. Furthermore, the Fe/SCN + PI system shows excellent anti-interference ability and application potential. This work pioneers the generation of active species using ETP's electron to activate oxidants, which provides a perspective on the design of single-atom catalysts via the charge-confined effect.

Atomically Dispersed Cobalt Anchored on Hollow Tubular Carbon Nitride Mediates Direct Electron Transfer and Oxygen-Related Active Species Path for Activation of Permonosulfate

Atomically dispersed catalysts anchored on nitrogen-rich substrates present promising application potential for the persulfate-based advanced oxidation process. Nevertheless, efficient activation efficiency and a clear activated mechanism of persulfate remain challenging in carbon nitride-based single-atom catalysts (SACs). To these, combined with the regulation strategy of metal-ligand section and carrier's architecture, an atomically dispersed Co single-atom catalyst anchored on regular hollow tubular carbon nitride (Co/TCN SAC) herein was devised and utilized to activate permonosulfate. As a result, Co/TCN SACs show excellent catalytic performance for the degradation of common antibiotics. Combined with X-ray absorption fine structure and theory calculation, it is confirmed that superficially anchored CoO3 sites of the Co2N2O2-CoO3 unit are the catalytic active center for peroxymonosulfate (PMS) activation. The electrochemical test and in situ electron paramagnetic resonance results demonstrate radical (SO4•- and •OH) and nonradical (electron transfer process and 1O2) paths contributing to the superior catalytic performance. In addition, the catalyst exhibits high reaction efficiency and structural stability considering water quality parameters. Finally, a continuous and efficient device was operated on a laboratory scale, which exhibited satisfactory efficiency in continuously removing electron-rich antibiotics such as tetracycline. This work reveals the atomic-level modulation of cobalt atomic sites on hollow tubular carbon nitride and their structure-activity relationship with persulfate activation.

Reconstructing the electron and spin structures of nanoscale iron sulfide through a biosurfactant layer towards radical-nonradical co-dominant regime

Radical-nonradical co-dominant pathways have become a hot topic in advanced oxidation, but achieving this on transition metal sulfides (TMS) remains challenging because their inherently higher electron and spin densities always induce radicals rather than nonradicals. Herein, a biosurfactant layer (BLR) was introduced to redistribute the electron and spin structure of nanoscale iron sulfide (FeS), which allowed both radical and nonradical to co-dominate the catalytic reaction. The resulting BLR-encased FeS hybrid (BLR@FeS) exhibited satisfactory removal efficiency (98.5 %) for hydrogen peroxide (H2O2) activation, outperforming both the constituent components [FeS (70.9 %) and BLR (86.2 %)]. Advanced characterizations showed that C, O, N-related sites (-CO and -NC) in BLR attracted electrons in FeS due to their strong electronegativity and electron-withdrawing capacity, which not only decreased electron density in FeS, but also resulted in a shift of the Fe/S sites from the high-spin to the medium-spin state. The reaction routes established by the BLR@FeS/H2O2 system maintained desirable stability against environmental interferences such as common inorganic anions, humic acid and changes in pH. Our study provides a state-of-the-art, molecule-level understanding of tunable co-dominant pathways and expands the targeted applications in the field of advanced oxidation.

The CoO-doped carbon nanotubes enhance electronic performance and effectively activate persulfate for the degradation of sulfafurazole

In recent studies, carbon nanotube (CNTs) materials and their composites have demonstrated remarkable catalytic activity in the activation of persulfate (PS), facilitating the efficient degradation of organic pollutants. In this study, a novel Co loaded carbon nanotubes (CoO@CNT) catalyst was prepared to promote PDS activation for the degradation of sulfafurazole (SIZ). Experimental results, the CNT as a carrier effectively reduces the leaching of cobalt ions and improves the electron transport capacity，whereas the introduced Co effectively activates the PDS, promoting the generation of highly reactive radicals to degrade SIZ. Under optimized conditions (a catalyst dose of 0.2 g/L, a PDS dose of 1 g/L and an initial pH = 9.0), the obtained CoO@CNT demonstrated favorable Fenton-like performance, reaching a degradation efficiency of 95.55% within 30 min. Furthermore, density functional theory (DFT) calculations demonstrate that the introduction of cobalt (Co) accelerates electron transfer, promoting the decomposition of PDS while facilitating the Co2+/Co3+ redox cycling. We further employed the environmental chemistry and risk assessment system (ECOSAR) to evaluate the ecological toxicity of intermediate products, revealing a significant reduction in ecological toxicity associated with this degradation process, thereby confirming its environmental harmlessness. Through batch experiments and studies, we gained a comprehensive understanding of the mechanism and influencing factors of CoO@CNT in the role of SIZ degradation, and provided robust support for evaluating the ecological toxicity of degradation products. This study provides a significant strategy for the development of efficient catalysts incorporating Co for the environmentally friendly degradation of organic pollutants.

Non-radical activation of low additive periodate by carbon-doped boron nitride for acetaminophen degradation: Significance of high-potential metastable intermediates

Metal-free environmental-friendly and cost-effective catalysts for periodate (PI) activation are crucial to popularize their application for micropollutant removal in water. Herein, we report that carbon-doped boron nitride (C-BN) can efficiently activate PI to degrade acetaminophen under very low oxidant doses (40 μM) and over a relatively wide pH range (3-9). As expected, the significant reduction in periodate addition is likely to be due to the higher chemical utilization efficiency achieved by a non-radical oxidation pathway. This involved two main mechanisms, the electron transfer process mediated by the high-potential metastable C-BN-900-PI* complex and singlet oxygen. In this case, the CO groups and defects on the C-BN surface were identified as key active sites for PI activation. Notably, the prepared C-BN-900 had good cycling performance and the degradation efficiency is recovered after simple annealing. The existence of HCO3- and HA significantly inhibited the reaction, whereas Cl-, SO42-, and NO3- had little effect on the degradation of ACE. Overall, this study provides a new alternative method to regulate the non-radical pathway of boron nitride/periodate system.

Self-assembly construction of 1D carbon nitride nanotubes and cobalt-modified for superior photocatalytic degradation of sulfonamide antibiotics

In the present work, a cobalt-doped carbon nitride nanotubes (Co-CNt) was synthesized via self-assembly process. Contributed to the narrow band gap, enlarged specific surface area and abundant active sites, Co-CNt has excellent photoelectric properties and superior performance than pristine CN in sulfisoxazole (SIZ) degradation under blue light irradiation, which achieved 100% removal within 40 min. Meanwhile, the system not only exhibited practical applicability by efficiently degrading SIZ, but also generating high levels of H2O2. Moreover, the Co-CNt/visible light system shows superior operability over a wide pH range, micro-concentration contaminants, various anions, water matrices and other sulfonamides with promising catalytic stability and applicability. The contribution of RSs in the degradation process were elucidated based on radical scavenging and spin-trapped tests, clarifying that O2·- and h+ majorly dominated the process. In addition, 4 probable degradation pathways of SIZ were provided and the generated intermediates' toxicity were evaluated. Overall, this study successfully synthesized a self-assembled 1D tubular photocatalyst with Co-doped and demonstrated the potential Co-CNt/visible light system for environmental remediation, providing a promising approach for the development of photocatalysis.