Mineralized cupric phosphate/alginate gel alternately multilayer-wrapped nanofibrous membrane with robust anti-crude oil pollution for oily wastewater purification

Abstract

The high oil-adhesion of crude oil results in flux decline. Therefore, the purification of crude oil/water emulsions is an ongoing and arduous challenge. To improve oil stain resistance and reusability, alginate gel and mineralized Cu3(PO4)2 were alternately layer-by-layer self-assembled on a thermally stabilized PAN/PEI nanofibrous membrane. Inspired by a natural formation water purification system, the hydrophilic and antifouling ‘soil-stone’-like hierarchical structures were constructed. The prepared membrane has excellent mechanical properties (Modulus:198.36 MPa) and large specific surface area. In addition, the synergistic effect of the alginate gel layer and mineralized copper phosphate endows the membrane with excellent underwater superhydrophobicity and outstanding anti-oil-fouling properties, so the (Alg/CuP)6-PAN/PEI membrane can effectively separate crude oil-in-water emulsions and other various SDS-stabilized oil-in-water emulsions, with a high separation efficiency of approximately 99.5%. In the continuous test of separating 1000 mL emulsion, the flux and separation efficiency have no obvious attenuation, and the flux recovery rate (FRR) reach up to 98.4%. Furthermore, the modified membrane has good mechanical and chemical stability in environments with ultrasonic waves, salt, solvents, bases and weak acids, showing great promise in the decontamination of actual oily wastewater.