Anti-biofouling membrane coated with polyvinyl alcohol/sodium carboxymethylcellulose/tannic acid hydrogel for efficient dye/salt separation

Biofouling is the most severe challenge for separation membranes. In this study, a metal-organic framework (MOF)-based mixed-matrix membranes (MMMs) with polyvinyl alcohol (PVA)/sodium carboxymethylcellulose (CMC)/tannic acid (TA) hydrogel coating exhibited a comprehensive anti-biofouling property and high efficient for dye/salt separation. For the hydrogel layer, ethanol inhibited the cross-linking of the hydrogen bond between the PVA, CMC and TA, forming a uniform "hydrogel paint" applied to the membrane surface using the coating method. Subsequently, the hydrogen bond was re-established by evaporating the ethanol. The hydrogel coating could form a dense hydrated layer, endowing the membrane with excellent anti-fouling properties, including oil, proteins, and bacteria. For the MOF-based MMMs layer, the skeleton structure of polyvinylidene fluoride anchored the bimetallic MOF crystals to mitigate the phenomenon of "trade-off". The hydrogel-coated MOFbased MMMs showed excellent properties, such as the water permeability was similar to 200 Lm(-2) h(-1), the rejection for Reactive Blue 19 was 100 %, the rejection for NaCl was 10.9 %, and it showed excellent stability for long-term service. Furthermore, the hydrogel-coated MOF-based MMMs presented a significant inhibitory effect on surface bacteria growth. In brief, this paper provided a new insight into preparing hydrogel-coated MOF-based MMMs, which had potential applications in separating dye/salt.