Ultrahigh adsorption capacity of anionic dyes with sharp selectivity through the cationic charged hybrid nanofibrous membranes

In the adsorption treatment of colored water, it's equally important to recover clean water and well separated dyes as well as reuse sorbent. Therefore, it is desired to develop adsorbents with prominent adsorption capacity, excellent selective adsorption for different dyes and robust chemical/mechanical stability. Herein, core-shell structured PDA/PEI@PVA/PEI nanofibrous membranes (NFMs), comprising uniform nanofibrous substrates and ultrathin PDA/PEI functional coating layer, were developed by a combination of PVA/PEI co-electrospinning and ultrathin PDA/PEI coating. The prepared NFMs exhibited excellent adsorption capacity for the anionic dyes and totally non-inductive to the cationic dyes on account of the strong electrostatic attraction/repulsion, which derived separation factor of anionic to cationic dyes as high as 970. The maximum adsorption capacity of PDA/PEI@PVA/PEI NFMs toward ponceau s and methyl blue were 1180 and 1290 mg/g, respectively, which is superior to the most results of current sorbents. Moreover, the hybrid NFMs demonstrated excellent chemical stability in the harsh environments and the frequent ad-/de-sorption cycling.