Effect of current density on groundwater arsenite removal performance using air cathode electrocoagulation |
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Authors: | Yanxiao Si Fang Zhang Hong Chen Guanghe Li Haichuan Zhang Dun Liu |
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Institution: | 1. School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, China2. Surface engineering division, Sinopec Petroleum Exploration and Production Research Institute, Beijing 100083, China3. School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China |
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Abstract: | ? With the same charge, current density had little effect on As(III) removal in ACEC. ? ACEC had the lowest energy consumption compared with EC/O2 or EC/N2. ? There was a trade-off relationship between energy consumption and removal time. ? The ·OH concentration in ACEC was 1.5 times of that in the EC/O2 system. Naturally occurring arsenic enrichment in groundwater poses a huge threat to human health. Air cathode electrocoagulation (ACEC) has recently been proposed to enhance As(III) oxidation and lower energy consumption. In this study, ACEC, EC/O2 and EC/N2 were evaluated with different current densities from 1 to 8 mA/cm2 to investigate the effect on As(III) removal in different redox environments. Current density had no appreciable effect on arsenic removal efficiency given the same charge in ACEC because the concentration ratio of Fe/H2O2 under different current densities remained stable. However, in EC/O2 and EC/N2, As(III) removal was inhibited at higher current densities (4–8 mA/cm2), likely because more Fe(II) competed with As(III) for the oxidant, leading to less effective oxidation of As(III). In all EC systems, the ·OH units generated per power consumption reached the highest value at the lowest current density. Compared with other EC systems, the ACEC system showed lower energy consumption at all current densities due to the low energy consumption of the electrode reaction and more free radical generation. A lower current density saved more energy at the expense of time, showing the trade-off relationship between energy consumption and removal time. The operation costs for As(III) removal under optimal conditions were calculated as 0.028?$/m3 for ACEC, 0.030?$/m3 for EC/O2, and 0.085?$/m3 for EC/N2 |
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Keywords: | Electrocoagulation Air cathode Arsenic Current density Energy consumption |
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