Towards the optimization of electro-bioremediation of soil polluted with 2,4-dichlorophenoxyacetic acid

The aim of this work is to study the optimization of electro-bioremediation (EBR) treatment of a 2,4-dichlorophenoxyacetic acid (2,4-D) polluted clay soil. The influence of two different variables were evaluated through batch experiments in a bench-scale electrokinetic setup using previously acclimated microbial cultures for 2,4-D biodegradation. First, it was studied the influence of the frequency applied in polarity reversal (PR): frequencies under study were 1, 2 and 6 d(-1), i.e., polarity changed every 24, 12 and 4 h respectively. The duration of experiments were 14 days and the electric field applied was 1.0 V cm(-1) (20 V) at room temperature. The second variable under study was the operation time, and based on the previous results, the selected frequency of PR was 2 d(-1) and three additional EBR experiments were conducted using different operation times (3, 7 and 10 days). Experiments without electric current (only biological contribution) for each operation time were simultaneously performed under the same experimental conditions as reference tests to check the influence of electrokinetics. Removal of 2,4-D from polluted clay soil was completed in 10 days. It was observed that solubility of the pollutant is a critical factor to ensure high removal efficiencies. Moreover, polarity reversal contributed to the successful results by maintaining correct pH values and reducing the removal of electrolytes from soil. By comparing the EBR results with the reference tests (without the contribution of EK phenomena), it was proved that the combination of bioremediation and electrokinetics has positive effects in the remediation of low permeable polluted soil. (C) 2020 Elsevier B.V. All rights reserved.