高级氧化技术是当今水处理技术领域研究的热点,Fenton试剂因操作简单、反应条件温和及氧化效率高等优势而备受关注。铁氧化物催化类Fenton反应能有效地解决催化剂回收利用难等问题,并且能够在较为广泛的pH范围内使用,从而成为Fenton氧化领域一个新的研究方向,但反应过程和机制往往更为复杂。本文评述了铁氧化物催化类Fenton反应中可能存在的多种机理,主要是羟基自由基理论、氧空位机理和高价态铁络合物机制。类Fenton反应速率的限速步骤是Fe(Ⅲ)/Fe(Ⅱ)循环过程,从提高反应速率的机理出发,本文探讨了类Fenton反应中铁氧化物催化剂的制备和发展,催化剂中多种价态的铁元素,通过相互间发生电子转移以加速Fe(Ⅱ)的再生,提高反应效率。铁氧化物掺杂过渡金属能显著提高催化H2O2有效分解的活性。阐明了多金属掺杂铁氧化物中多金属组分的催化机制和铁氧化物结构形态对反应性能的影响。研究表明催化剂中铁的结构形态、催化剂比表面积、催化剂与H2O2之间电子转移速率等都是决定催化剂性能的重要因素。最后讨论了继续研究方向,为开展非均相类Fenton反应提供参考。
Advanced oxidation processes(AOPs) have attracted much attention in the field of water or wastewater treatment.As one of the most investigated AOPs,Fenton reagents have notably advantages of convenient operation,mild condition and high performance of degradation.Iron oxide catalyzed Fenton-like reaction,which can be operated effectively in wide range of pH values with convenient catalyst separation and reutilization,has been intensively investigated as one of the most promising developments of Fenton-like reaction during the past two decades.However,when compared with traditional Fenton reagents,these iron oxides initiated Fenton-like processes often encounter much more complicated reaction steps.The main mechanisms are reviewed,including radical mechanism,oxygen vacancies mechanism and high-valent iron species mechanism.The rate of Fe(Ⅱ) generation or Fe(Ⅲ) reduction in pure iron oxides is greatly limited and the circulation of Fe(Ⅲ)/Fe(Ⅱ) has demonstrated to be the rate-controlling steps of Fenton-like reaction.In order to accelerate this limiting step and improve the reactivity of Fenton-like reaction,modified catalysts including multivalent iron mixtures and transition metal doped iron oxides are developed.Before describing the catalytic performance,effects of modification on the morphology,structure and element composition of iron oxides are examined profoundly.Results show that the speciation of iron,the specific surface area of catalysts and the electron transfer between H2O2 and iron oxide are all playing an important role in the reactivity of Fenton-like reaction.The future development and investigations of heterogeneous catalysts are also discussed.