SO3H covered nanofiltration composite membrane by taurine for selective removal of anionic solutes

Abstract

ABSTRACT Nanofiltration (NF) membranes have already been widely used owing to the merits of high permeability, energy saving, and selective separation. Here, a convenient way to prepare a functional layer of a composite NF membrane was investigated, which used taurine to replace a part of piperazine (PIP) in the aqueous phase in interfacial polymerization to decrease the cross-linking density of the polyamide network. Although the molecular weight cutoff by the membrane decreased to 2,000 Da, the interception to sulfates and negatively charged dyes was strengthened. As the taurine ratio increased, the surface layer thinned, and pure water permeation improved, but MgSO4 rejection showed a tendency of ‘first-increase-then-decrease’ under the synergism of size exclusion and the Donnan effect. At the apex ratio of 4:1 (taurine: PIP), the T80 membrane showed >98% retention to sulfates, MgSO4, Na2SO4, and (NH4)2SO4, and >98.7% rejection to anionic dyes, methyl blue, congo red, and acid chrome blue K (ABK). The film also exhibited excellent fouling resistance to emulsified oil, humic acid, and bovine serum albumin, and fractionation of ABK and NaCl.