Robust anti-fouling superhydrophilic organic–inorganic mineralized coating for effective long-term separation of crude-oil-in-water emulsions
Jiqun Li, Yan Zhang, Shiyu Song, Yifan Ma, Jianlin Yang
Abstract
Membrane separation technology offers an ideal strategy for the efficient separation of emulsified oily wastewater by constructing superhydrophilic coatings on porous substrates. However, coatings exhibit more susceptible to fouling, leading to a decline in separation performance. Herein, a robust and durable superhydrophilic polydopamine/polyethyleneimine (PDA/PEI)-MgCO 3 mineralized coating with resistance to crude-oil fouling was successfully developed via co-deposition coupled with biomineralization. The mineralization effect of the PDA/PEI adhesive layer and organic dextran enabled uniform dispersion of inorganic MgCO 3 nanocrystals across PDA/PEI co-deposited substrates. More importantly, polypropylene membrane with PDA/PEI-MgCO 3 coating exhibited high separation flux (>925 L m −2 h −1 bar −1 ), exceptional efficiency (99.6 %), and long-term stable cyclic separation capability (98.9 % flux recovery) for crude-oil-in-water emulsions containing surfactant. Anti-crude-oil-fouling mechanism of the mineralized coating was further elucidated using density functional theory calculations. There is a strong adsorption interaction between the CO 3 2− in MgCO 3 and water molecules, demonstrating excellent hydration capacity. The synergistic effect of the hydrophilic CO 3 2− functional groups in the mineralized coating and the surface nanocomposite structure significantly enhances its hydration capacity, exhibiting exceptional resistance to crude-oil fouling. Additionally, the PDA/PEI-MgCO 3 coating demonstrates excellent chemical durability and prolonged stability, showing its strong potential for large-scale treatment of emulsified crude-oil-containing wastewater.