Pore fluid pH-salinity homogenization for sustained electroosmosis: Performance, energy efficiency and underlying mechanisms.

Electroosmosis facilitates fluid transport in low-permeability soils and is widely used in electrokinetic remediation. Its application is hindered by a progressive decline in flow rate and a concurrent increase in specific electrical energy consumption. The pH and salinity have been identified as the most relevant variables affecting electroosmotic flow (EOF). However, a synergistic and process-based regulation of pore fluid properties remains insufficiently developed. This study proposes a pore fluid pH-salinity homogenization conditioning (PFHC) method that stabilizes electrochemical conditions and maintains ion availability through electrolyte circulation and electrolysis isolation. PFHC increased the electroosmotic flow rate by 141%, with an additional 62% improvement under optimal conditions (pH = 10, electrolyte concentration = 0.01 mol L-1). Moreover, it reduced specific electrical energy consumption by approximately 50% compared to conventional anodic pH control methods. In addition, predictions of EOF rate evolution based on the Helmholtz-Smoluchowski electroosmotic model are found to be more accurate for PFHC-treated tests, clarifying underlying mechanisms of PFHC and the model's applicability. This improved agreement indicates that zeta potential governs electroosmotic permeability only when sufficient ionic strength is maintained. This study provides a process-based strategy for sustaining electroosmosis and offers practical guidance for energy-efficient electrokinetic remediation.