The contrastive study of chemical treatment on the properties of PVDF/PFSA and PVDF/PVP ultrafiltration membranes

• Chemical cleaning has less effect on PVDF/PFSA membranes than PVDF/PVP membranes.
• Alkali or hypochlorite cleaning leads PVDF/PFSA membranes to be more hydrophilic.
• Hypochlorite cleaning leads PVDF/PVP membranes to be more easily fouled.
• Chemically treated PVDF/PFSA membranes have superior mechanical properties.

The impact of chemical treatment on the poly(vinylidene fluoride)/perfluorosulfonic acid (PVDF/PFSA) hollow fiber ultrafiltration membranes in acid, alkali and hypochlorite solutions was contrastively studied with PVDF/polyvinylpyrrolidone(PVP) ultrafiltration membranes. The morphologies, surface properties, permeation performances, antifouling ability and mechanical properties of the membranes were characterized by numerous state-of-the-art analytical techniques. The results reveal that the chemical treatment has less effect on the PVDF/PFSA membranes than on the PVDF/PVP membranes. After treating with alkali and hypochlorite solutions, the surface hydrophilicity of PVDF/PFSA membranes increases, while the surface hydrophilicity of PVDF/PVP membranes decreases. In comparison with the original membranes, the antifouling ability of the PVDF/PFSA membranes is improved, while the antifouling ability of the PVDF/PVP membranes declines. Compared with the chemically treated PVDF/PVP membranes, the treated PVDF/PFSA membranes are more easily regenerated after fouling. The chemical treatments lead to the decline of the mechanical strength in different degrees for both PVDF/PFSA and PVDF/PVP membranes. Nevertheless, this influence on PVDF/PFSA membranes is evidently less severe than on PVDF/PVP membranes.