Carboxylated multi-walled carbon nanotubes (MWCNTs-COOH)-intercalated graphene oxide membranes for highly efficient treatment of organic wastewater

GO/CNTs composite membranes with fine hierarchical nanostructure were facilely fabricated by intercalation with 1D carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) into 2D graphene oxide (GO) nanosheets for efficient organic wastewater treatment. By characterization results of XRD, Raman, FTIR, TEM and water contact angle, MWCNTs-COOH was successfully to be intercalated into GO lamellar interlayers with grafting reactions, which would improve water permeated flux and stability of membrane. The influences of GO/ CNTs ratios, loading amounts, CNTs types and support types on the membrane separation performance were systematically investigated towards methylene blue dye solution. For the GO/CNTs composite membranes prepared under the optimized conditions, the permeated flux of 34.4 L m(-2) h(-1) and rejection over 99.7 % were obtained towards methylene blue solutions under the transmembrane pressure difference of 0.9 bar, respectively. Compared with pristine GO membrane, it exhibited a nearly 10-fold water permeated flux improvement meanwhile maintaining high rejection. Moreover, the electrostatic interaction and size exclusion effects were synergistically contributed to be responsible for the efficiently separation properties of the GO/CNTs membranes towards different positively/negatively charged dyes and neutral organic molecules. Such the GO/CNTs membranes also exhibited good chemical stability for acid resistance with highly efficient separation performance.