Core-shell PPy@TiO2 enable GO membranes with controllable and stable dye desalination properties

Graphene oxide membranes (GOMs) have great potentials in the high-performance desalination of salty wastewater. However, the low-selectivity and fouling issues are the main obstacles to practical implementation. Although compositing with TiO2 nanoparticles alleviates such problems by regulating membrane structures and photodegrading surface organic filter cakes, the performance is still limited by the intrinsic aggregation feature and narrow UV response range. Here, we functionalize TiO2 nanoparticles with polypyrrole (PPy) to improve their dispersibility and visible-light-driven photodegradation properties. The as-formed core-shell heterostructures (PPy@TiO2) with a large dose are intercalated into GOM, resulting in a large water flux (436.93 Lm−2h−1bar−1) and selective positive dye/negative dye separation with a maximum salt permeation of 97%. Upon the reduction of the dosage, more than 99% of dyes are separated regardless of molecule weights and surface charge polarity although the average water flux is reduced to 5.83 Lm−2h−1bar−1 and the salt rejection rate is increased up to 24%. In addition, the composite membrane with low-dosed PPy@TiO2 photodegrades MB completely within 2 h, while its water permeability and dye rejection performance are maintained after a 5 h filtration process. Our work provides a facile method to develop multi-functional 2D composite membranes with controllable and stable dye desalination performances.