Oil fouling threatens the water flux stability of membranes for oil/water separation. Simple hydrophilic modification fights for an opportunity to prevent oil contamination but fails to eliminate severe water flux decline. In essence, a “single‐defense” mechanism is insufficient to build a potent barrier against accumulated cake layer under a filtration environment. This work reports a “double‐defense” design by integrating hydrophilic polymer brushes and hydrogel layer on oil/water separation membranes for desired anti‐oil‐fouling property, where a poly(vinylidene fluoride) porous membrane is first covered by a layer of poly(hydroxyethyl methylacrylate) hydrogel and then controllably grafted with poly(sulfobetaine) brushes. The spatially hierarchical structure establishes a highly covered “double‐defense” barrier for the membrane surface to efficiently repel oil adhesion and the formation of an accumulated cake layer. When separating various surfactant‐stabilized oil‐in‐water emulsions, the permeating flux displays a nearly zero decline throughout the whole filtration period. Most importantly, the permeating flux of the membrane is almost the same when filtrating pure water and filtrating oil‐in‐water emulsions, which is difficult to be achieved by the general membranes, indicating that the membrane has excellent anti‐oil‐fouling property superior to the currently reported membranes.

No abstract

Effective dye separation and desalination are critical for the treatment of highly saline textile wastewater with dye mixtures. In this study, a graphene oxide (GO) membrane with a tunable interlayer distance (d) was fabricated to generate clean water via two-stage filtration, namely, the dye/ salt separation and desalination stages. In the first stage, under low pressure (e.g., 0.3 MPa), the membrane with a d value of ca. 7.60 Å was suitable for removing the dye from the saline wastewater. The dye and salt (i.e., Na 2 SO 4 ) rejection rates of >99% and <6.5% were achieved, respectively, indicating the significant potential to recycle the dyes from the highly saline dye wastewater. In the second stage, under a higher pressure (e.g., 0.8 MPa), the d value was reduced to ca. 7.15 Å, bestowing the membrane with a desalination function. The desalination rate of a single filtration process could reach up to 51.8% from 1.0 g/L saline (i.e., Na 2 SO 4 ) water. The as-prepared membrane also exhibited excellent practical advantages, including ultrahigh permeability, significant antifouling (against dye) performance, and excellent stability. Furthermore, with the stacking of multistage filtration systems, the proposed membrane technology will be capable of regenerating dye and producing clean water.

Two‐dimensional (2D) MXene‐based nanofiltration membranes could sustainably and rapidly produce clean water. However, the challenges related to the severe swelling of the MXene membranes in water should be overcome before the practical application. In this work, the negatively charged MXene‐based membrane is modified by positively charged polyethyleneimine (PEI) with various PEI:MXene ratios. The PEI‐MXene is deposited on a polyacrylonitrile (PAN) substrate as a top membrane to prepare an anti‐swelling composite PEI‐MXene/PAN membranes with outstanding mechanical strength and stability. Interestingly, when the interlayer spacing of the top Mxene layers are tuned between ca. 14.15 and ca. 14.52 Å, the resultant PEI‐MXene/PAN membranes exhibit the excellent ability of size sieving. For instance, PEI‐MXene(1:1)/PAN membrane presents high flux performance to Acid Blue 90 (AB90), Congo Red (CR), and Direct Red 80 (DR80) (i.e., 563.9, 882.6, and 633.6 L m−2 h−1, respectively) at 0.2 MPa, and remarkable rejection rates, that is, 99.3%, 99.82%, and 99.9%, respectively. Besides, the PEI‐MXene(0.5:1)/PAN possesses the highest flux of 1528.1 L m−2 h−1 and outstanding rejection rate of 99.9% to dye of AB8GX. Moreover, the proposed strategy can be extended to the modification of other 2D material nanofiltration membranes.image

No abstract

No abstract

No abstract

<p>Supplemental Figure legends for Figures S1-S5</p>