Effect of the structure of stacked electro-Fenton reactor on treating nanofiltration concentrate of landfill leachate

The membrane concentrate from landfill leachate has great potential risks of the environmental pollution. The aim of this study was to investigate the structure effect of stacked electro-Fenton (EF) reactor on the nanofiltration (NF) concentrate treatment from landfill leachate. The stacked EF reactor was constructed with a carbon-PTFE gas diffusion cathode and an IrO2-Ta2O5 anode with different electrode spacings (i.e., 2, 5, 10, and 40 mm) and electrode pairs (i.e., 1, 3, 6, and 9). Results showed that smaller electrode spacing and more electrode pairs in the stacked EF reactor improved the COD removal in the NF concentrate treatment. The specific energy consumption decreased with smaller electrode spacing but increased with more electrode pairs. Under the current density of 15 mA cm(-2), Fe2+ dosage of 560 mg L-1, the stacked EF reactor with 9 electrode pairs and the electrode spacing of 2 mm removed 71 +/- 6% of the total COD in the NF concentrate within 6 h and the specific energy consumption was 207 +/- 20 kWh center dot kg COD-1. The COD removal was kept stable in the stacked EF reactor within 3 cycles of operation. Three-dimensional fluorescence spectroscopic and gas chromatographic mass spectrometric analysis showed that humic acids and aromatic proteins were efficiently degraded in the EF process and large amount of aromatic hydrocarbons was detected in the treated NF concentrate. Our stacked EF reactor could be used to treat leachate concentrates with effectively degradation of the refractory organic pollutants. (C) 2018 Elsevier Ltd. All rights reserved.