Investigation on the characteristics of water transport in nanochannels under an electric field

Abstract

Fluid transport in nanochannels driven by an electric field is a promising approach for shale oil and gas extraction and membrane separation. However, the fundamental mechanism of this process under the combined conditions of nanoconfinement and geological formations is not fully understood. This study constructs an alumina nanochannel system with pore diameters ranging from 26.1 to 206.2 nm. Pressure-driven experiments (0.01–0.1 MPa) were conducted to compare the transport characteristics of deionized water and simulated formation water (2% KCl). During these experiments, electric fields were applied either parallel or perpendicular to the flow direction. The objective was to decouple the interconnected influences of nanoconfinement, ion effects, and the electric field. The results demonstrate that measured flow rates were lower than the values predicted by the classical Hagen-Poiseuille theory in all experimental scenarios. The effect of the electric field on flow was ion-dependent. For deionized water, the electric field did not alter the flow rate. In contrast, for the simulated formation water, a parallel electric field increased the flow rate by an average of 14.3%, and a perpendicular electric field increased it by an average of 5.5%. Through systematic experiments, this study reveals the combined effects of nanoscale confinement, electric field, and ionic environment on fluid transport. The multi-parameter control design allows for the differentiation of influences from various mechanisms that affect flow rate changes, providing a theoretical basis for understanding transport phenomena in nanochannels under complex conditions.