The effect of reduction degree of GO nanosheets on microstructure and performance of PVDF/GO hybrid membranes

In this study, the effect of the reduction degree of GO nanosheets on the microstructure and performance of PVDF/GO membranes were systematically investigated via comparing four PVDF/GO membranes synthesized by the casting solutions prepared at 50, 70, 85 and 100 C, which were denoted PVDF/GO-50, PVDF/GO-70, PVDF/GO-85 and PVDF/GO-100, respectively. X -Ray Photoelectron Spectrometer (XPS) and Raman Spectroscopy results showed that the preparation temperature of the casting solution affected the reduction degree of GO nanosheets. Higher preparation temperature resulted in a higher degree of reduction. Compared with the pure PVDF membrane, PVDF/GO membranes achieved better performance in term of membrane flux and rejection. However, the optimal loading of GO nanosheets was dependent on the reduction degree. For the PVDF/GO-50 membrane, the maximal membrane flux (46 L/m(2) h) was reached at a GO loading of 0.5%, while the membrane flux of the PVDF/GO-100 membrane increased with GO loading in the range of 0-2%. SEM and AFM characterization results also showed that both GO loading and reduction degree of GO influenced the pore structure and surface roughness of PVDF/GO membranes. It is worth noting that the mechanical strength of the PVDF/GO membranes was weaker than that of the pure PVDF membrane at all GO reduction degrees regardless GO loading. This indicates that the integrity of PVDF membranes might be impaired by GO nanosheets. (C) 2015 Elsevier B.V. All rights reserved.