Preparation and characterization of polylactic acid-modified polyvinylidene fluoride hollow fiber membranes with enhanced water flux and antifouling resistance

Abstract

Although ultrafiltration (UF) membranes have gained considerable attention in water separation and purification process, most of the materials used for commercial UF membranes fabrication do not able to degrade/decompose easily and tend to cause severe environmental problem when they are discarded. In view of this, an environmentally friendly hydrophilic polymeric material - polylactic acid (PLA) has been considered in this work, aiming to reduce not only the environmental impacts caused by the existing membranes but also to improve membrane water flux and antifouling resistance. In this study, the effects of PLA quantity and air gap (during spinning process) on the morphology and liquid separation performance of polyvinylidene fluoride (PVDF) hollow fiber membranes were investigated. The membrane properties were characterised using scanning electron microscope, atomic force microscope Fourier transform Infrared spectrometer, tensile tester and contact angle goniometer before filtration experiment was conducted. Results showed that the incorporation of small quantity of PLA (with PLA/PVDF weight ratio of ≤ 1.0) could significantly improve membrane water flux from ˜30 to 376.7 L/m2.h.bar without compromising rejection (95–97%). More importantly, the PLA-modified PVDF membranes required much lower temperature to decompose which minimizes environmental impacts. Owing to the improved surface hydrophilicity (lower water contact angle), the PLA-modified PVDF membranes also exhibited higher flux recovery rate than that of pure PVDF membrane, revealing the improved antifouling resistance against bovine serum albumin. The findings of this work demonstrated that biodegradable PLA is potential to be used to modify the characteristics of UF membranes, leading to enhanced water treatment process.