A novel peroxymonosulfate activation process by single-atom iron catalyst from waste biomass for efficient singlet oxygen-mediated degradation of organic pollutants

Magnetic CoFe hydrotalcite composite Co metal-organic framework material efficiently activating peroxymonosulfate to degrade sulfamethoxazole: Oxygen vacancy-mediated radical and non-radical pathways

Herein, a novel rich oxygen vacancy (Ov) cobalt-iron hydrotalcite composite cobalt metal-organic framework material (ZIF-67/CoFe-LDH) was prepared by simple urea water and heat reduction approach and utilized for the peroxymonosulfate (PMS) system to remove sulfamethoxazole (SMX). 95 ± 1.32 % SMX (20 mg/L) was able to degraded in 20 min with TOC removal of 53 ± 1.56 % in ZIF-67/CoFe-LDH/PMS system. The system maintained a fantastic catalytic capability with wide pH range (3-9) and common interfering substances (Cl-, NO3-, CO32-, PO42- and humic acid (HA)), and the degradation efficiency could even remain 80.2 ± 1.48 % at the fifth cycle. Meanwhile, the applicability and feasibility of the catalysts for practical water treatment was verified by the degradation effects of SMX in different water environments and several other typical pollutants. Co and Fe bimetallic active centers synergistically activate PMS, and density functional theory (DFT) predicted adsorption energy about Ov in ZIF-67/CoFe-LDH for PMS was 1.335 eV, and OO bond length of PMS was stretched to 1.826 Å. As a result, PMS was more easily activated and broken, which accelerated the singlet oxygen (1O2), sulfate radical (SO4•-), high-valent metals and other reactive oxygen species (ROS). Radical and non-radical jointly degrading the pollutants improved the catalytic effect. Finally, SMX degradation intermediates were analyzed to explain the degradation pathway and their biotoxicity was also evaluated. This paper provides a new research perspective of oxygen vacancy activating PMS to degrade pollutants.

Natural biomass derived single-atom catalysts for energy and environmental applications

Single atom catalysts (SACs) excel in various chemical processes, including electrocatalysis and industrial chemistry, due to their efficiency. In contrast to chemically synthesized precursors, biomass offers a greener and more cost-effective approach for SACs fabrication. To date, over forty types of SACs have been synthesized using natural sources like starch, cellulose, lignin, hemicellulose, proteins, and chitin. These catalysts incorporate metals such as Fe, Co, Ni, Cu, Zn, Mn, and Pt. This review concentrates on the preparation of SACs from biomass, exploring innovative techniques and their extensive applications in energy conversion and environmental conservation, including but not limited to reactions involving oxygen reduction, oxygen evolution, and hydrogen evolution. It also discusses current challenges and prospective advancements in this domain. This paper updates and expands on the knowledge of SACs derived from biomass, aiming to foster the development of more effective, low-cost catalyst materials from natural sources.

Lattice-Confined Single-Atom Catalyst: Preparation, Application and Electron Regulation Mechanism

Lattice-confined single-atom catalyst (LC SAC), featuring exceptional activity, intriguing stability and prominent selectivity, has attracted extensive attention in the fields of various reactions (e.g., hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), etc.). To design a "smart" LC SAC for catalytic applications, one must systematically comprehend updated advances in the preparation, the application, and especially the peculiar electron regulation mechanism of LC SAC. In this review, the specific preparation methods of LC SAC based on general coordination strategy are updated, and its applications in HER, OER, ORR, N2 reduction reaction (NRR), advanced oxidation processes (AOPs) and so forth are summarized to display outstanding activity, stability and selectivity. Uniquely, the electron regulation mechanisms are first and deeply discussed and can be primarily categorized as electron transfer bridge with monometallic active sites, novel catalytic centers with polymetallic active sites, and positive influence by surrounding environments. In the end, the existing issues and future development directions are put forward with a view to further optimize the performance of LC SAC. This review is expected to contribute to the in-depth understanding and practical application of highly efficient LC SAC.

Biochar Meets Single-Atom: A Catalyst for Efficient Utilization in Environmental Protection Applications and Energy Conversion

Single-atom catalysts (SACs), combining the advantages of multiphase and homogeneous catalysis, have been increasingly investigated in various catalytic applications. Carbon-based SACs have attracted much attention due to their large specific surface area, high porosity, particular electronic structure, and excellent stability. As a cheap and readily available carbon material, biochar has begun to be used as an alternative to carbon nanotubes, graphene, and other such expensive carbon matrices to prepare SACs. However, a review of biochar-based SACs for environmental pollutant removal and energy conversion and storage is lacking. This review focuses on strategies for synthesizing biochar-based SACs, such as pre-treatment of organisms with metal salts, insertion of metal elements into biochar, or pyrolysis of metal-rich biomass, which are more simplistic ways of synthesizing SACs. Meanwhile, this paper attempts to 1) demonstrate their applications in environmental remediation based on advanced oxidation technology and energy conversion and storage based on electrocatalysis; 2) reveal the catalytic oxidation mechanism in different catalytic systems; 3) discuss the stability of biochar-based SACs; and 4) present the future developments and challenges regarding biochar-based SACs.

Single-atom Mn-embedded carbon nitride as highly efficient peroxymonosulfate catalyst for the harmful algal blooms control

In recent years, water quality deterioration caused by harmful algal blooms (HABs) has become one of the global drinking water safety issues, and sulfate radical driven heterogeneous advanced oxidation technology has been widely used for algae removal. However, the shortages of low active site exposure, metal leaching, and secondary contamination limit its further application. Therefore, the single-atom Mn anchored on inorganic carbon nitride was constructed to enhance the oxidation and coagulation of algal cells while maintaining cell integrity in this study. The removal efficiency of Microcystis aeruginosa was as high as 100 % within 30 min under the optimal conditions of 400 mg/L single-atom Mn-embedded g-C3N4 (SA-MCN) and 0.32 mM peroxymonosulfate (PMS). Importantly, the K+ release, malondialdehyde concentration, floccules morphology and variation of algal organic matters further showed that the algal cells still maintained high integrity without severe rupture during the catalytic reaction. Furthermore, the catalytic mechanisms of algae removal by moderate oxidation and simultaneous coagulation in this system were explored by quenching experiments, EPR analysis, theoretical calculation, and Zeta potential. In brief, this study highlighted the single-atom heterogeneous catalyst with high-efficiency and environmental-friendliness in harmful algal blooms control.

Antibiotic removal from synthetic and real aqueous matrices by peroxymonosulfate-based advanced oxidation processes. A review of recent development

The widespread use of antibiotics for the treatment of bacteriological diseases causes their accumulation at low concentrations in natural waters. This gives health risks to animals and humans since it can increase the damage of the beneficial bacteria, the control of infectious diseases, and the resistance to bacterial infection. Potent oxidation methods are required to remove these pollutants from water because of their inefficient abatement in municipal wastewater treatment plants. Over the last three years in the period 2021-September 2023, powerful peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) have been developed to guaranty the effective removal of antibiotics in synthetic and real waters and wastewater. This review presents a comprehensive analysis of the different procedures proposed to activate PMS-producing strong oxidizing agents like sulfate radical (SO4•-), hydroxyl radical (•OH, radical superoxide ion (O2•-), and non-radical singlet oxygen (1O2) at different proportions depending on the experimental conditions. Iron, non-iron transition metals, biochar, and carbonaceous materials catalytic, UVC, photocatalytic, thermal, electrochemical, and other processes for PMS activation are summarized. The fundamentals and characteristics of these procedures are detailed remarking on their oxidation power to remove antibiotics, the influence of operating variables, the production and detection of radical and non-radical oxidizing agents, the effect of added inorganic anions, natural organic matter, and aqueous matrix, and the identification of by-products formed. Finally, the theoretical and experimental analysis of the change of solution toxicity during the PMS-based AOPs are described.