Enhancement of lead removal from soil by in-situ release of dissolved organic matters from biochar in electrokinetic remediation

This study investigated the release of dissolved organic matters (DOMs) from biochar under DC electric field and the roles of the released DOMs on the removal of heavy metal lead (Pb) from the soil coupled with electrokinetic (EK) remediation. The fluorescence excitation and emission matrix spectra (EEM) analysis suggested biochar could discharge more DOMs under the DC field, while biochar from 300 °C (B300) could release much more DOMs than biochar obtained under the 500 °C and 700 °C (B500 and B700). The major component of the released DOMs was likely the humic-like substances, which exhibited a strong ability to complex with Pb and extract them from the soil matrix. By using B300 as a permeable reactive barrier (PRB) to combine with EK under 0.96 V cm−1, Pb migration rates in the soil and the global Pb removal were improved by about 2.8-fold and 1.1-fold, respectively. By employing B700 as another PRB, installed close to the cathode of reactor, the migration rate and removal of Pb could be greatly enhanced. This study provides new insights into the biochar application for sustainable EK remediation of the soil contaminated with heavy metal species.