Effect of electroosmosis flow and electrolyte circulation on electrokinetic remediation of Pb-contaminated kaolin

Adding acetic acid to specific kaolin induces reverse electroosmotic flow (EOF). The experimental results indicate that the pH of the kaolin after experimentation ranged from 3.78 to 10.48, which did not reach the point of zero charge (pH_PZC) identified by previous studies as the critical factor causing the reverse EOF. This reverse EOF was attributed to the differential water-binding capabilities of ions, with hydration numbers of CH₃COO⁻ and Na⁺ being 6 and 5, respectively, and the distinct migration mechanisms of various ions, notably the unique chain migration of H⁺. EDTA was utilized to complex Pb into PbEDTA²⁻, thereby altering its ionic charge and facilitating its application in the electrokinetic remediation (EKR) of acetic acid-acidified, Pb-contaminated kaolin. This intervention was crucial as it induced the migration of anionic Pb towards the anode. To mitigate polarization near the electrodes, the electrolytes of the anode and cathode were linked and circulated. The results demonstrated a successful Pb removal rate of up to 97.44% while retaining the kaolin's inherent elements, indicating that electrolyte circulation helps maintain soil fertility during EKR by preserving ionic components essential for plant growth.