Preparing carbonated water-bio-heavy oil emulsions via membrane emulsification for efficient interphase mass transfer desalination

Bio-heavy oil with high oxygen content and combustion calorific value has attracted lots of attention as a green and sustainable fuel to cope with the increasingly severe energy shortages. However, the high salt content limits its combustion utilization due to potential risks such as equipment corrosion and wear blockage. The traditional desalination method using sulfuric acid causes a large amount of wastewater, Herein, we propose an assisted metal-ion interphase mass transfer desalination strategy by preparing carbonated water-in-bio-heavy oil (CW/O) emulsions with continuous membrane emulsification. α-Al₂O₃ membrane with an average pore size of 600 nm was selected as the emulsification medium. Saturated carbonic acid solutions as a dispersed phase were pressed through the membrane pores into bio-heavy oil to form uniform micron-sized CW/O emulsions. The prepared CW/O droplets provide a large interphase mass transfer interface which assists the hydrolysis of fatty acid salts of bio-heavy oil in the acidic environment and yields an efficient transfer of metal ions. As a result, the CW/O emulsion with an average droplet size (D_3,2) of 4.29 μm and a specific surface area of 139.63 m²/m³ was prepared at a pressure of 0.5 MPa, achieving a salt removal efficiency of up to 85.62 %. This study provides a novel chemical-free and effective strategy for efficient oil product refining while utilizing CO₂ through the continuous preparation of micron-sized CW/O droplets with sufficient interphase mass transfer area.