Volume 67

Molecular-to-Macroscopic Interfacial Remodeling of Oil-Water Systems under DC Electric Fields: Mechanisms and Applications in Enhanced Recovery and Wastewater Treatment Qiang Li,Zhengfu Ning, Jun Li,Kangbo Zhao,Xiqian Zheng,Yuheng Yang,Zejiang Jia

Abstract

This study investigates how DC electric fields (0-15 V) regulate interfacial properties and compositional evolution in crude oil–water systems. By integrating IFT and interfacial viscosity measurements with aqueous chemical analysis, SARA fractionation, GC, and FTIR, we reveal correlations between aqueous electrochemistry and molecular restructuring of crude oil. Electrolysis at the cathode increased aqueous pH to 12.97, promoting ionization of native acids and in-situ formation of carboxylates; correspondingly, IFT dropped from 12.63 to 0.08 mN·m-1. Interfacial viscosity decreased sharply with voltage, while SARA and molecular analyses showed depletion of asphaltenes, ~eightfold growth of polar resins, ~9.6% rise in branched alkanes, and ~32% increase in the CH3/CH2 ratio. These coupled aqueous–oil transformations explain the collapse of interfacial film strength under DC electrolysis and suggest a dual mechanism: aqueous alkalinization activates the interface, while electrochemically induced molecular restructuring weakens it. The findings directly inform electrochemical EOR and demulsification strategies.

Keywords DC electric field; Interfacial tension; Molecular reconstruction; Carboxylation; Electrorheological synergy; enhanced oil recovery