Aminopolycarboxylic acids modified oxygen reduction by zero valent iron: Proton-coupled electron transfer, role of iron ion and reactive oxidant generation

• DOI: 10.1016/j.jhazmat.2022.128402
• Publication Date: 2022-02-01T16:52:56Z
• Authors: Qi Wang; Yuwei Pan; Wenyang Fu; Huizhong Wu; Minghua Zhou; Ying Zhang
• Keywords: Nitrilotriacetic acid; EDDS; Ethylenediaminetetraacetic acid; Zerovalent iron; Ethylene diamine; Degradation

The oxygen reduction reaction (ORR) activated by Fe0 in the presence of three aminopolycarboxylic acids (CAs), i.e. nitrilotriacetic acid (NTA), ethylenediamine-N,N'-disuccinic acid (EDDS) and ethylenediaminetetraacetic acid (EDTA), for the degradation of sulfamethazine (SMT) was investigated. At optimum conditions, Fe0/EDDS/O2, Fe0/EDTA/O2 and Fe0/NTA/O2 systems presented SMT removal of 58.2%, 75.3% and 93.8%, respectively, being much higher than that in the Fe0/O2 system (1.36%). The generation of surface-bound Fe2+ (Fe2+) and dissolved iron ion was enhanced by CAs. ORR through a two-electron transfer pathway was mainly responsible for H2O2 generation in NTA and EDTA systems, while a single-electron ORR was the major source for producing H2O2 in EDDS system. •OH produced by the homogeneous reaction of Fe2+ and H2O2 was the main species for SMT degradation. Fe0/EDDS/O2 produced more 1O2 than Fe0/EDTA/O2 and Fe0/NTA/O2; however, the radical contributed negligibly to SMT removal. The caging effect of CAs might be a major factor influencing the reaction rate of Fe2+ and O2. CAs provided protons to accelerate the electron transfer, the production of Fe2+ and thus the contaminant removal. This study is of great significance for revealing ORR mechanisms in the Fe0-chelate system.