Abstract: According to the technology of electric restoration for heavy metal contaminated soil, this paper adjusted the pH value by adding humic acid buffer solution to the cathode region to improve the electro-osmotic drainage effect, and compared the final drainage effect from multiple aspects. The relation between drainage rate and ζ potential was deduced. The results were explained at the points of ζ potential, metal ion and fulvic acid’s complexation to metal ion. The results show that adding humic acid to cathode region cannot increase the drainage accumulation, and soft clay with high humic acid concentration is not suitable for large-scale electro-osmotic drainage and consolidation.

Key words: humic acid buffer, cathode pH control, ζ potential, electrokinetic remediation, drainage