Superhydrophilic membranes have drawn much attention owing to
their outstanding anti-fouling performance and ultrahigh permeation
flux for wastewater treatment and oil–water separation. Since most
widely used polymer membranes have high intrinsic hydrophobicity,
a universal approach for superhydrophilic modification is highly
required. Yet, how to simply transform highly hydrophobic
membranes into superhydrophilic ones is still a challenge. Herein, we
develop a one-step and general strategy to achieve the hydrophobicto-superhydrophilic transformation of commercial membranes on the
basis of catechol chemistry,i.e., co-deposition of tannic acid (TA) and
3-aminopropyltriethoxysilane (APTES) in aqueous solution. Owing to
the distinct adhesion properties of TA and the reaction between the
oxidative product of TA and the hydrolysis product of APTES, hydrophilic and hierarchical layer-colloidal nanospheres can bein situ
assembled on various highly hydrophobic membranes including polyvinylidene fluoride (PVDF), polypropylene (PP), polytetrafluoroethylene (PTFE), copper mesh, stainless steel wire, and nylon mesh.
The resulting superhydrophilic membrane can realize high-efficiency
separation of various oil-in-water emulsions.