Polydopamine-CaCO3 modified superhydrophilic nanocomposite membrane used for highly efficient separation of oil-in-water emulsions

A superhydrophilic/underwater superoleophobic CaCO3@PDA@nylon nanocomposite membrane was prepared by a simple dip-coating method using a nylon 66 membrane in dopamine and nano CaCO3 particle aqueous solutions. The prepared CaCO3@PDA@nylon membrane was characterized by SEM, EDS, FTIR, and XPS. The underwater oil contact angle reached 159.7 degrees. The modified membrane showed highly efficient oil-in-water emulsion separation performance for various viscous oils or organic solvents over a wide range from 126.8 to 6029.6 nm. Furthermore, the CaCO3@PDA@nylon membrane also demonstrated high permeation flux and good regeneration ability. Even with continuous reuse of 15 cycles, the flux was still high, e.g., 517.3 L m- 2 h-1 for chloroform-in-water emulsions with an average particle size of 126.8 nm. The modified membrane's possible oilin-water emulsion separation mechanism was obtained by combining fluorescence-assisted dripping, continuous filtration, and emulsion contact angle experiments. This work might provide a simple and environmentally friendly membrane modification method for general separation studies of high oil concentration oil-in-water emulsions. The simple preparation process and efficient and fast separation ability highlight its great potential in large-scale production and oily wastewater treatment.