Degradation of carbamazepine over MOFs derived FeMn@C bimetallic heterogeneous electro-Fenton catalyst

Co-engineering of Fe-Mn nanoclusters with porous carbon for enhanced electrocatalytic ammonia synthesis

Electrochemical nitrate reduction (NO3-RR) to produce ammonia (NH3) is a promising strategy for treating nitrate contaminants but is limited by poor electrocatalyst activity and sustainability. Here, a nanocluster oxide iron-manganese loaded on nitrogen/oxygen-doped porous carbon catalyst is developed, achieving an NH3 yield rate of 359.87 μmol h-1 cm-2 and a high faradaic efficiency of 87.73%. Furthermore, the Zn-NO3- battery with NC-Fe1Mn2/NOPC as the cathode exhibits a high peak power density of 0.31 mW cm-2 and a NH3 yield of 25.79 μmol h-1 cm-2.

Stability challenges of transition metal-modified cathodes for electro-Fenton process: A mini-review

Electro-Fenton (EF) process with transition-metal (TM) modified cathode has been regarded as a green and promising technology for wastewater treatment. Recently, breakthroughs in boosting catalyst activity for both two-electron oxygen reduction reaction (2e- ORR) and Fenton's reaction have gained intensive attention. However, achieving long-term stability of catalysts remains challenging, but is decisive for large-scale applications. This minireview provides fundamental understanding on the activity-stability correlation and the deactivation mechanisms of TM-based catalysts in EF systems, focusing on physical and chemical evolution, metal dissolution, catalyst detachment and structure collapse during long-term electrolysis. Subsequently, ongoing efforts from catalyst design to electrode engineering to stabilize the metal active sites are highlighted. Finally, the challenges and future perspectives in developing active and durable TM-modified cathodes are discussed, serving as a roadmap towards the large-scale application of EF process for wastewater treatment.

Shell-induced enhancement of Fenton-like catalytic performance towards advanced oxidation processes: Concept, mechanism, and properties

Fenton-like advanced oxidation processes (AOPs) are commonly used to eliminate recalcitrant organic pollutants as they produce highly reactive oxygen species through the reactions between the catalysts and oxidants. Recently, considerable attention has been directed towards shell-structured Fenton-like catalysts that offer high stability, maximum utilization of active sites, and exceptional catalytic performance. In this review, we have introduced the concept of several typical shell-forming architectures (e.g., hollow structure, core-shell structure, yolk-shell structure, particle-in-tube structure, and multi-shelled structure), elucidating their role in promoting Fenton-like reaction catalysis through the nanoconfinement mechanism. In each aspect, the correlation between the shell-induced effects and the Fenton-like catalytic performance is highlighted. Finally, future challenges and opportunities for the development of shell-structured Fenton-like catalysts towards AOPs are presented, offering bright practical application prospects.

Recent progress in electro-Fenton technology for the remediation of pharmaceutical compounds in aqueous environments

The global focus on wastewater treatment has intensified in the contemporary era due to its significant environmental and human health impacts. Pharmaceutical compounds (PCs) have become an emerging concern among various pollutants, as they resist conventional treatment methods and pose a severe environmental threat. Advanced oxidation processes (AOPs) emerge as a potent and environmentally benign approach for treating recalcitrant pharmaceuticals. To address the shortcomings of traditional treatment methods, a technology known as the electro-Fenton (EF) method has been developed more recently as an electrochemical advanced oxidation process (EAOP) that connects electrochemistry to the chemical Fenton process. It has shown effective in treating a variety of pharmaceutically active compounds and actual wastewaters. By producing H2O2 in situ through a two-electron reduction of dissolved O2 on an appropriate cathode, the EF process maximizes the benefits of electrochemistry. Herein, we have critically reviewed the application of the EF process, encompassing diverse reactor types and configurations, the underlying mechanisms involved in the degradation of pharmaceuticals and other emerging contaminants (ECs), and the impact of electrode materials on the process. The review also addresses the factors influencing the efficiency of the EF process, such as (i) pH, (ii) current density, (iii) H2O2 concentration, (iv) and others, while providing insight into the scalability potential of EF technology and its commercialization on a global scale. The review delves into future perspectives and implications concerning the ongoing challenges encountered in the operation of the electro-Fenton process for the treatment of PCs and other ECs.

Single-Atom Iron Catalysts with Core-Shell Structure for Peroxymonosulfate Oxidation

The chemical tolerance of ketoenamine covalent organic frameworks (COFs) is excellent; however, the tight crystal structure and low surface area limit their applications in the field of catalysis. In this work, a porous single-atom iron catalyst (FeSAC) with a core-shell structure and high surface area was synthesized by using Schiff base COF nanospheres as the core and ketoenamine COF nanosheets growth on the surfaces. Surface defects were created using sodium cyanoborohydride etching treatment to increase specific surface area. The dye degradation experiments by peroxymonosulfate (PMS) catalyzed by the FeSAC proved that methylene blue can be degraded with a degradation rate constant of 0.125 min-1 under the conditions of 0.1 g L-1 catalyst dosage and 0.05 g L-1 peroxymonosulfate. The FeSAC/PMS system effectively degrades various pollutants in the pH range of 4-10 with over 80% efficiency for four cycles and can be recovered by soaking in iron salt solution. Free radical quenching experiments confirmed that singlet oxygen and superoxide radicals are the main active species for catalysis.

Flower-like Ni/Mn/MC microspheres derived from metal-organic frameworks for electrocatalytic degradation of ceftriaxone sodium

This study demonstrated the design and fabrication of flower-like Ni/Mn-MOFs materials, and three-dimensional ultrathin flower-like Ni/Mn/MC microspheres were fabricated by embedding metal or metal oxide nanoparticles into a porous carbon skeleton via high-temperature pyrolysis at 600 °C and used for the electrocatalytic degradation of ceftriaxone sodium. This unique ultrathin porous flower-like structure can expose more active sites, provide rapid ion/electron transfer, and improve electrocatalytic activity. Meanwhile, the excellent electrical conductivity of the carbon skeleton, as well as the rational composition and synergistic effect of the two components, can promote the generation of active radicals (•OH and •O2-) in the reaction system, which accelerates the electrochemical degradation process and improves the electrocatalytic degradation performance. The results showed that the Ni/Mn/MC-5:1 composite prepared when the molar ratio of Ni: Mn was 5:1 exhibited the best electrocatalytic degradation performance for the degradation of sodium ceftriaxone. The composites showed 98.2% degradation of ceftriaxone sodium in 120 min and maintained sound degradation after 20 cycles. Therefore, we concluded that this novel multicomponent composite has good electrocatalytic activity and stability for the degradation of antibiotic wastewater.

Fabrication and performance of novel multifunctional sodium alginate/polyvinylpyrrolidone hydrogels

In this work, a novel alginate/polyvinylpyrrolidone (SA/PVP-Fe) hydrogel spheres were prepared by cross-linking with Fe2+ ions after blending sodium alginate with polyvinylpyrrolidone. The degradation performance of the hydrogels was assessed through the degradation of phenol, achieving 100% degradation and about 64% total organic carbon (TOC) mineralization within 60 min (initial concentration of phenol = 20 mg/L; H2O2 concentration = 5 mM; initial pH = 6.5; catalyst dosage = 1.0 g/L). Degradation kinetics were monitored using high-performance liquid chromatography (HPLC). The structural and chemical properties of the hydrogels were characterized using scanning electron microscopy (SEM), energy spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Inductively coupled plasma mass spectrometry (ICP-MS). Additionally, the hydrogels exhibited multiple reuse cycles, albeit with a gradual decline in degradation performance. Mechanistic investigations revealed that the hydroxyl radical derived from the Fenton reaction was the primary active species responsible for the degradation process. This research provides valuable insights into improving the mechanical properties of sodium alginate hydrogels, opening up avenues for their practical applications.

The resin-supported iron-copper bimetallic composite as highly active heterogeneous Fenton-like catalysts for degradation of gaseous toluene

In this study, a resin-supported iron-copper bimetallic heterogeneous Fenton catalyst with excellent removal performance, superior economy and outstanding recoverability was synthesized by an impregnation method and used to remove gaseous toluene. Experiments disclosed that 3-FeCu@LXQ-10 possessed extremely high catalytic capacity. At a temperature of 30 °C, an initial toluene concentration of 200 mg/m3 and H2O2 atomization amount of 3 mmol/h, the toluene removal efficiency of 3-FeCu@LXQ-10 was 97.50%. Experimental tests had revealed that the bimetallic supported catalysts exhibited higher catalytic activity than single metal-supported catalysts, owing to an interaction effect between iron and copper metal ions. Furthermore, electron paramagnetic resonance (EPR) and radical quenching tests were carried out, and the results indicated •OH radicals performed a key role in the Fenton-like process. In addition, the iron-copper bimetallic catalysts exhibited good reusability and stability characteristics during six degradation cycles. This study shows promising potential in using FeCu@LXQ-10 as a heterogeneous catalyst for removing toluene.

Accelerated electron transfer process via MOF-derived FeCo/C for enhanced degradation of antibiotic contaminants towards heterogeneous electro-Fenton system

The Fe(III) to Fe(II) process limits the rate of the electro-Fenton system. In this study, MIL-101(Fe) derived porous carbon skeleton-coated FeCo bimetallic catalyst Fe₄/Co@PC-700 was prepared as a heterogeneous electro-Fenton (EF) catalytic process. The experimental results showed its good performance in catalytic removal of antibiotic contaminants, the rate constant of tetracycline (TC) degradation catalyzed by Fe₄/Co@PC-700 was 8.93 times higher than that of Fe@PC-700 under the pH conditions of raw water (pH = 5.86), exhibited good removal of TC, oxytetracycline (OTC), hygromycin (CTC), chloramphenicol (CAP) and ciprofloxacin (CIP). It was shown that the introduction of Co promoted more Fe⁰ production, allowing the material to exhibit faster Fe(III)/Fe(II) cycling rates. ¹O₂ and high-priced metal oxygen species were identified as the main active species of the system, in addition to the analysis of possible degradation pathways and toxicity of intermediates of TC. Finally, the stability and adaptability of Fe₄/Co@PC-700 and EF systems to different water matrices were evaluated, showing that Fe₄/Co@PC-700 was easy to recover and could be applied to different water matrices. This study provides a reference for the design and system application of heterogeneous EF catalysts.