A smart gating microfiltration membrane to break aperture adaptability limit for industrial oily wastewater treatment

Smarting gating microfiltration membranes that can adjust the pore size according to the composition of the wastewater are expected to solve the problem of membrane's limited adaptability to complex oily wastewater. However, the design of a responsive adjustment system capable of manipulating micropore sizes and constant wettability remains a dilemma. Herein, an innovative fiber-based membrane (named PAN/PNIPAm-CF/MWCNT/FeOOH) was developed by skillful introducing poly (n-isopropylacrylamide) (PNIPAm) microgels into the porous channel of the sieve layer. By controlling the physical collapse of PNIPAm microgels, the micro-sized pores have been successfully reversibly adjusted from small size at room temperature to large size when exposed to high temperature, while not changing their wettability. Under a flux conversion rate of more than 200 %, the PAN/PNIPAm-CF/MWCNT/FeOOH membrane could quickly pretreat complex oily wastewater discharged from production lines with high temperature (removal of large oil droplets), then carry out in-depth purification at low temperature (removal of emulsified oils, metal ions, dye micelles, etc.). Besides, the PAN/PNIPAm-CF/MWCNT/FeOOH membrane showed good stability and resistance to harsh environment during long-term filtration. Thereby, the design of fiber-based membranes with micropore smart control capability and constant wettability provides innovative ideas for industrial complex oily wastewater treatment.