Graphene oxide/sodium alginate nanofiltration membrane with double cross-linked structure for high-performance in dye separation

Carbon materials have wide applicability in water purification, so graphene oxide (GO), which has tunable physicochemical properties, has great potential in molecular separation. Here, a method to precisely control the interlayer spacing by double cross-linking of sodium alginate (SA) and multivalent cations is reported. In this work, SA was first uniformLy anchored on the surface of GO nanosheets to form composite nanosheets (GO-SA), and then multivalent cations (Ba2+/Fe3+) were added to complete the crosslinking reaction and finally assembled into membranes (M/GO-SAx). The results show that the additional GO-SA component enlarged the nanochannels, and the water permeability of GO membranes is up to 72.29 L m(-2) h(-1) bar(-1). Compared with the traditional GO membrane, the water permeability is increased by 3.5 times. Meanwhile, the composite nanofiltration membrane exhibits decent dye screening performance and the rejection rate of Methylene blue (MB) and Rhodamine B (RB) was more than 99%. At the same time, the multivalent cations that participate in the membrane construction affect the performance of the membrane, and this makes the screening ability of the membrane for dyes significantly better. These studies provide new ideas and methods for designing nanofiltration membranes, which can be used to design and develop new nanofiltration membranes for water treatment.