Dual-biomimetic superwetting silica nanofibrous membrane for oily water purification

Developing a feasible and cost-effective membrane which can remediate highly emulsified oily water, especially those stabilized by surfactants, is of great significance but challenging. In this work, a biomimetic superwetting silica nanofibrous membrane (SNFM) with hierarchical structures, interconnected pores as well as high porosity was developed by the facile combination of electrospinning and a dual-bioinspired method. Bioinspired adhesive (polydopamine/polyethylenimine, PDA/PEI) with positively charged active sites was first linked onto silica nanofiber (SNF) surface via Michael addition reaction and then the membrane roughness was constructed by assembling the negatively charged silica nanoparticles (SNPs) via electrostatic attraction. The resultant membrane exhibits a superwetting performance with a water contact angle of 0° in air and an oil contact angle of 165 ± 3° underwater. Moreover, the hierarchically structured SNFM displays strong acid/alkali resistance, outstanding thermal stability, robust flexibility and high mechanical strength. As a poof-of-concept, the hierarchical SNFM integrated into a wastewater separation tank achieves a high water flux over 7152 and 1120 L m⁻² h⁻¹ when treating oil-in-water microemulsion (1000 mg L⁻¹) with and without surfactant, respectively. The dual-bioinspired method can be used as a universal tool to construct material surface roughness for application in other selective separation fields.