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

Abstract

Coconut shell biochars prepared from the oxygen free pyrolysis under 300–700 °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 °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. • The removal of 2,4,6-trichlorophenol by electrokinetic remediation with biochar was increased by about 2 folds. • Biochar enhanced trichlorophenol migration, adsorption, and degradation in soil. • The optimum removal was obtained at 2 V cm −1 using the biochar from 700 °C.