Enhanced 2,4,6-trichlorophenol removal from soil by electrokinetic remediation coupled with biochar in a permeable reactive barrier

Coconut shell biochars prepared from the oxygen free pyrolysis under 300-700 degrees C were incorporated in the permeable reactive barrier (PRB) for electrokinetic remediation (EK) to remove 2,4,6-trichlorophenol (2,4,6-TCP) from soil. The result indicated the removal of 2,4,6-TCP from the soil under EK was increased by about 2 folds using biochar in PRB than those without biochar PRB. The orthogonal test suggested that the voltage input rather than the pyrolysis temperature of biochar was the major factor governing the removal of TCP during the EK-PRB process. The optimum TCP removal reached over 55% under 2 V cm-1 of voltage, 700 degrees C pyrolysis temperature and 40 mg L-1 of initial TCP concentration. The roles of biochar during EK remediation were identified as three aspects: accelerating the migration of TCP in soil by enlarging the electroosmotic flow (EOF), enhancing the direct removal of TCP by adsorption, and promoting the electrochemical degradation of TCP. The biochar from high pyrolysis temperature was preferred to be coupled with EK for the removal of organic contaminants owing to its great ability of enhancing EOF as well as pollutant adsorption. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Coconut shell biochars prepared from oxygen-free pyrolysis were used in a permeable reactive barrier (PRB) for electrokinetic remediation (EK) to remove 2,4,6-trichlorophenol (2,4,6-TCP) from soil. The addition of biochar to the PRB significantly increased the removal of 2,4,6-TCP compared to PRB without biochar. The voltage input was found to be the major factor influencing the TCP removal during the EK-PRB process. The optimal conditions for TCP removal were found to be 2 V cm-1 voltage, 700 degrees C pyrolysis temperature, and 40 mg L-1 initial TCP concentration. The biochar played multiple roles in EK remediation, including enhancing electroosmotic flow, adsorbing TCP, and promoting electrochemical degradation. Biochar from high pyrolysis temperature was particularly effective in enhancing electroosmotic flow and pollutant adsorption.