Key Takeaways & Executive Findings
- •• • Carbon materials significantly enhance KMnO4 oxidation, with graphene oxide accelerating degradation of trace organic pollutants like sulfisoxazole, sulfamethazine, and bisphenol A, as demonstrated by Wang et al. • • Two primary mechanisms drive pollutant degradation in KMnO4/CMs systems: electron transfer mediation by carbon materials and generation of reactive manganese species, with carbon materials acting as electron transfer mediators to accelerate electron transfer between pollutants and KMnO4. • • Regeneration of deactivated carbon materials is achievable: thermal treatment at >350 °C under inert gas or chemical reduction removes surface oxygen groups, restoring catalytic performance; for example, reduced graphene oxide pyrolyzed at 700 °C for 2 h under nitrogen regained its sp2 structure and catalytic activity. • • Organic solvent washing (e.g., ethanol, hexane, acetone) or ultrasonic treatment can remove adsorbed intermediates or MnO2 deposits, recovering catalytic activity without structural damage, as shown for graphite.
Abstract
Potassium permanganate (KMnO4) oxidation is a promising technology for organic pollutant removal in water due to its low cost and broad pH applicability. However, its moderate oxidation capacity results in slow degradation rates for refractory organic compounds. Carbon materials (CMs), known for their accessibility, stability, and environmental compatibility, have shown great potential in enhancing KMnO4 oxidation. This paper provides a comprehensive review of recent advancements on the enhancement of KMnO4 oxidation of organic pollutants by CMs. The performance and suitability of various CMs in improving KMnO4 oxidation were systematically compared. Additionally, two key mechanisms driving the degradation of organic pollutants in the KMnO4/CMs system were elucidated, along with a discussion on the recycling and regeneration of CMs. Finally, future research directions and development trends for this technology were outlined, aiming to offer insights to advance the practical application of KMnO4/CMs system in water treatment.
1. Introduction
Potassium permanganate (KMnO4) oxidation is widely employed in water treatment due to its low cost, ease of storage and handling, and broad pH applicability. However, its moderate oxidation potential (E0 = 1.67 V in acid, 1.23 V in neutral, 0.56 V in alkaline) and selectivity toward electron-rich moieties (e.g., phenols, amines, alkenes) result in slow degradation kinetics for refractory organic pollutants. Conventional enhancement strategies, such as homogeneous ligands (phosphate, pyrophosphate, EDTA, humic acid), redox mediators, metal-based catalysts, and external energy inputs (electrochemical, ultrasonic, UV), suffer from secondary pollution risks or high energy consumption, hindering practical application.
Carbon materials (CMs), characterized by large specific surface area, high porosity, excellent electronic conductivity, and chemical inertness, have emerged as effective activators for KMnO4 oxidation. Recent studies demonstrate that incorporating CMs such as graphene oxide, carbon nanotubes, and reduced graphene oxide significantly accelerates the oxidative removal of various organic micropollutants. This review systematically summarizes the performance of different CMs, elucidates the underlying mechanisms (electron transfer and reactive species generation), and discusses recycling and regeneration strategies. The findings provide a foundation for optimizing KMnO4/CM systems for efficient and sustainable water treatment.
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LI Junjie, LIANG Zhijie, ZHANG Jing, MA Jun (2026). Research Progress on Potassium Permanganate Activated by Carbon Materials for Degradation of Organic Pollutants. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2024120203
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Frequently Asked Questions
What are the primary mechanisms by which carbon materials enhance KMnO4 oxidation of organic pollutants?
Two key mechanisms are identified: (1) carbon materials act as electron transfer mediators, accelerating electron transfer between pollutants and KMnO4; (2) they facilitate the generation of reactive manganese species (e.g., Mn(III) or Mn(V)) that enhance oxidation. The relative contribution depends on the carbon material's surface chemistry and structure.
How does the pH of the solution affect the performance of KMnO4/CM systems?
pH directly influences KMnO4's redox potential and the speciation of reduction products. In acidic conditions (E0 = 1.67 V), oxidation is strongest, while in neutral (E0 = 1.23 V) and alkaline (E0 = 0.56 V) conditions, the oxidizing power decreases. Carbon materials can mitigate pH effects by promoting electron transfer, but optimal performance is often observed in neutral to slightly acidic conditions.
What are the main causes of carbon material deactivation during repeated use, and how can they be regenerated?
Deactivation primarily arises from surface oxidation (formation of oxygen-containing groups) and blockage by adsorbed intermediates or MnO2 deposits. Regeneration methods include thermal treatment at >350 °C under inert gas (e.g., 700 °C for 2 h for reduced graphene oxide) to remove oxygen groups, or washing with organic solvents (ethanol, hexane, acetone) to desorb organic species. Ultrasonic treatment can also remove MnO2 without structural damage.
What are the scalability and cost implications of using carbon materials to activate KMnO4 in industrial water treatment?
Carbon materials like graphene oxide and carbon nanotubes are relatively expensive, but their high efficiency and potential for regeneration may offset costs. The review highlights that carbon materials are stable and can be reused multiple times, though performance may decline. Future research should focus on developing cost-effective, high-performance carbon materials and efficient regeneration methods to enhance economic viability.
What are the future research directions for KMnO4/CM systems?
Future work should explore modified carbon materials (e.g., doped or functionalized) to improve reaction efficiency and lifespan, develop greener regeneration methods, precisely tune carbon structure and surface properties for targeted pollutant degradation, and investigate confinement effects to accelerate reactions at nanoscale. These efforts aim to overcome current limitations and broaden practical applications.
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