Bio-inspired co-deposited preparation of GO composite loose nanofiltration membrane for dye contaminated wastewater sustainable treatment

The fully separation of dye/salt through loose nanofiltration membranes is of great significance for the sustainable development paradigm of textile wastewater. However, the current loose nanofiltration membranes suffer low separation efficiency and complex preparation. Herein, by one-step co-deposition, we develop graphene oxide (GO) composite loose nanofiltration membranes with low negatively charged surface. Our membrane possesses unconventional high pure water permeation of 71.7 LMH/bar, 92.9 % rejection for Methyl blue (MB) and 98.8 % rejection for Congo red (CR). Benefiting from the large interlayer distance of GO nanosheets and low negatively charged surface, membrane achieves high dyes/salts separation with satisfactory permeation to salts (94.3 % of Na2SO4, 97.6 % of MgSO4, 98.3 % of MgCl2 and 99.0 % of NaCl). The CR/salt mixed solutions exhibit similar removal rates to their constituents' single dye or salt solutions (CR rejection is up to more than 97% and the permeations of all salts are above 93 %). At the same time, binary dyes mixtures (Congo red and Methyl orange) can also be effectively separated. Furthermore, the membrane shows a relatively desirable antifouling property. The flux recovery still remains at 85.9 % after three cycling filtrations. This study provides a facile approach to prepare highly-efficient loose nanofiltration membranes for wastewater sustainable remediation.