Interfacially crosslinked composite porous membranes for ultrafast removal of anionic dyes from water through permeating adsorption

The dye wastewater is one of the most difficult industrial wastewaters to treat. It keeps a big challenge to realize fast removal of dyes from water by membrane filtration due to the trade-off between separation selectivity and permeation flux for ultrafiltration or nanofiltration (NF) process. Here we report novel composite porous membranes which can remove anionic dyes from water by ultrafast permeating adsorption. A crosslinked polyethyleneimine (PEI) polymer with strong adsorption ability was incorporated onto a nylon microfiltration membrane by the interfacial amidation reaction between PEI and trimesoyl chloride. The obtained composite membranes were used for the decolorization of dye solution by permeation mode. It was shown that the composite membranes were able to nearly completely remove anionic dyes in acidic conditions with high permeation fluxes. In an optimized case, the adsorption capacity of Sunset Yellow for the composite membranes reached 0.7   mg/cm 2 with a high flux of 85   L/m 2   h under a ultralow pressure of 0.01   bar. This flux was far much higher than that of NF membranes, about 10   L/m 2   h   bar. The pH-dependent electrostatic interaction between PEI and anionic dyes was responsible for the rapid dye removal. The adsorption saturated membranes could be effectively regenerated by a simple alkaline washing.