Superhydrophilic and Degradable PLA Fiber Membrane With Silica Layer for Oil-in-Water Emulsion Separation

A superhydrophilic polylactic acid (PLA) fiber membrane was fabricated by developing a hydrophilic silica surface layer on electrospun fibers. The drawn fibers were twisted and activated in an ethanol solution, leading to the shrinkage of the membrane and enhancing surface hydrophilicity, as well as reducing the pore size of the membrane. Through the coupling of 3-aminopropyltriethoxysilane, silica was polymerized in situ on the fiber surface of the electrospun PLA membrane to achieve a superhydrophilic surface. The membrane underwent degradation in a sodium hydroxide aqueous solution at a rate of 2.240 min⁻¹. The membrane was employed for separating surface-stabilized oil-in-water emulsions. The oil droplet sizes in the filtrates were 93, 169, and 132 nm, respectively. The water flux of the membrane for ionic oil-in-water emulsions reached 3205 L·m⁻²·h⁻¹, attributed to the electrostatic effect on the membrane surface (35.35 eV) and the sieving effect of the pore channel (0.918 μm). In contrast, the water flux for nonionic emulsions was only 350 L·m⁻²·h⁻¹. Furthermore, after immersing the membrane in the hydrolysis of tetraethyl orthosilicate again, the oil retention rate remained at 98.6%, and the water flux recovery rate was sustained at 96.3% over 30 cycles of separating oil-in-water emulsion.