Regenerable adsorptive membranes prepared by mussel-inspired co-deposition for aqueous dye removal

Preparation process and mechanism of the adsorptive membrane for dye removal. [Display omitted] •An adsorptive membrane was designed by mussel-inspired co-deposition of DA and PEI.•The adsorptive membrane could rapidly and selectively remove anionic dyes.•The adsorptive membrane showed excellent acid and alkali resistance.•The adsorptive membrane after service was highly regenerable. In this work, we report on a regenerable and robust adsorptive membrane with superb dynamic adsorption capacity towards dyes prepared by a controllable mussel-inspired co-deposition of dopamine (DA) and polyethyleneimine (PEI) on a polyvinylidene fluoride (PVDF) microfiltration membrane. The DA oxidative self-polymerization occurred to form polydopamine for high adhesion with the PVDF membrane. On the other hand, the PEI provided a large number of amino groups with high adsorption ability, and had both Michael addition and Schiff base reaction with DA to induce covalent interaction for high stability. In addition, the co-deposition process was controlled to happen on the membrane surface and inside the membrane bulk pores simultaneously. By these ingenious designs, the prepared adsorptive membrane thus showed high dynamic adsorption capacity (up to 188 mg g−1) and ultra-high removal ratio (＞99.9%) towards typical anionic dye of methyl blue. Not only that, the membrane could separate rapidly and selectively anionic dyes from dye mixtures. More importantly, the adsorptive membrane showed highly regenerative ability in NaOH solution (after 6 recovery cycles, the treating efficiency maintained higher than 95%), and good durability with robust resistance in acidic and alkaline environments. This work affords an innovative strategy and insight in fabricating the adsorptive membrane using mussel-inspired co-deposition for organic dye removal in water.