To improve the removal efficiency of low-concentration organic pollutants and enhance the oxidation efficiency of electro-Fenton (EF) process, a floating sandwich-type EF system (N/(A)/D-EF) without aeration was constructed for the first time. This EF system electro-synthesized H2O2 through the floating natural air diffusion electrode (NADE) without aeration, and regenerated Fe(II) effectively by the activated carbon fiber (ACF) interlayer, which significantly enhanced the process oxidation capacity since its •OH yield was 8.7 times that of the conventional EF system. In addition, the ACF interlayer could adsorb and enrich micro-pollutants and the generated •OH directly oxidize the pollutants adsorbed on the ACF, which enabled regeneration of ACF and maintained removal stability in 20 consecutive experiments. The removal rate constant (k) of carbamazepine by N/(A)/D-EF process was 7.6 times and 2.1 times higher than that of conventional EF and ACF adsorption process, respectively. This process could efficiently remove mixed low-concentration organic pollutants (0.1 mg L-1) in domestic sewage and lake water with rate constant 1.6-7.1 times that of the conventional EF process but lower energy consumption. Meanwhile, the N/(A)/D-EF process had a wider application range of sewage pH and conductivity, which was a promising process for removing low-concentration pollutants in wastewater.
Keywords: Adsorption; Electro-Fenton; Micropollutants; Natural air diffusion electrode; Oxidation.
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