Microwave-assisted Demulsification of Water-in-oil Emulsions: Effects of Heating Dynamics, Dielectric Properties, and Energy Consumption

Microwave irradiation has attracted considerable attention as a promising physical approach for destabilization of water–oil emulsions; however, the mechanisms governing microwave-assisted phase separation under non-equilibrium conditions remain insufficiently understood. In the present study, water-in-oil emulsions prepared from crude oils produced in the Absheron oilfields of Azerbaijan were subjected to controlled microwave treatment at power levels of ۲۰۰, ۴۰۰, ۶۰۰, and ۸۰۰ W. Emulsions with different water volume fractions were investigated to evaluate the influence of microwave power, heating-rate evolution, dielectric behavior, rheological response, interfacial tension variation, droplet-size distribution, and specific energy consumption on demulsification performance. The scientific novelty of the work lies in the integrated investigation of dielectric, rheological, interfacial, thermal, and microscopic characteristics together with time-dependent heating-rate dynamics during microwave-assisted demulsification. Unlike conventional temperature-oriented approaches, the present study considers the coupled influence of transient structural rearrangement, interfacial polarization, and kinetic response under non-equilibrium microwave exposure. The obtained results revealed a pronounced non-monotonic dependence of phase separation efficiency on microwave power. Although increasing microwave power accelerated heating and increased bulk temperature, the highest separation efficiency was achieved within an intermediate power range of ۴۰۰–۶۰۰ W. At ۸۰۰ W, separation efficiency decreased despite intensified thermal response, indicating the onset of excessive structural activation and reduced phase disengagement. Supplementary dielectric, rheological, interfacial tension, droplet-size distribution, and microscopy analyses suggested that microwave-assisted demulsification is governed not only by bulk thermal effects, but also by coupled dielectric and interfacial phenomena associated with structural evolution during irradiation. Evaluation of the E/A parameter further demonstrated that intermediate microwave powers provide the most favorable balance between separation efficiency and energy consumption. The obtained results contribute to a broader physicochemical understanding of microwave-induced phase evolution in heterogeneous liquid systems under non-equilibrium conditions.

کلیدواژه ها:

Microwave demulsification ، Water-in-oil emulsions ، Heating rate dynamics ، Interfacial polarization ، Energy-efficient separation