Bimetallic Fe/Al system: An all-in-one solid-phase Fenton reagent for generation of hydroxyl radicals under oxic conditions

In the classic Fenton reaction, both H2O2 and ferrous ion (Fe(II)) are required under a narrow low pH range to produce hydroxyl radicals (OH center dot). The modified Fenton processes including heterogeneous Fenton-like reaction, photo-Fenton reaction and electro-Fenton reaction developed to overcome the drawbacks of the homogeneous Fenton reaction have recently received increasing attention. However, all the modifications of the classic Fenton reaction cannot be assembled into one system and require external supply of reagents or energy. We present here, bimetallic Fe/Al, a novel solid-phase Fenton reagent capable of in situ generation of H2O2 and Fe(I1) to form OH center dot under near neutral pH conditions without an external energy supply. Aluminum acts as an electron donor to maintain the electron supply and preserve the outer layer of iron at the zero-valence state with enhanced surface areas. The production of OH center dot by bimetallic Fe/Al was quantified and further detected by an electron paramagnetic resonance (EPR) analysis under oxic conditions. Radical scavenging tests were performed by adding isopropanol or 1,4-benzoquinone in the system to investigate the nature of the oxidants produced during the oxidative process. Bimetallic Fe Al system for the Fenton reaction in water involves both surface-mediated and aqueous-phase reactions. A pilot scale test using a continuous-flow column packed with Fe/A1 (9.8 kg) demonstrated the capability of bimetallic Fe/Al for COD removal of acidic dye solutions. The novelty of bimetallic Fe Al is that it is an all-in-one solid-phase Fenton reagent that can be readily applied to a wide variety of environmental applications. (C) 2019 Elsevier B.V. All rights reserved.