Layer-by-layer assembly of high negatively charged polycarbonate membranes with robust antifouling property for microalgae harvesting

To tailor low-biofouling membranes remains one of the most problematic issues in filtration for microalgae harvesting. The aim of this study is to develop a high negatively charged and hydrophilic membrane to reduce membrane fouling via bioinspired design and Layer-by-layer (LBL) self-assembly technique for the application in microalgae harvesting. Bioinspired adhesive based on the polydopamine and polyethylenimine (PDA/PEI) composite was first linked onto the neutrally charged PC membrane substrates, then the poly-(styrenesulfonate) (PSS)/poly-(diallyldimethylammonium chloride) (PDADMAC) layers were uniformly assembled by electrostatic attraction. The resultant highly negatively charged and hydrophilic PC membranes exhibit a zeta potential of -66.1 mV and a water contact angle of 26°. Moreover, the modified membranes present a high average flux (133.1 L m2 h-1·bar-1) in 1-h microalgae filtration, a high algae retention (~100%) as well as a high flux recovery rate (over 94%). Meanwhile, the resultant membranes exhibit excellent chemical stability in high salty solutions, the low pH solutions and tolerance to long-time running in DI water. The combination of bioinspired construction method and LBL self-assembly technique could be expected to be a universal way to endow neutrally charged materials with highly negative or positive surface charge for various applications.