Preparation of hollow fibre braided polyvinylidene fluoride membranes by dip coating for membrane aerated bioreactor

Abstract

In this work, hollow fibre polyvinylidene fluoride (PVDF) supported membranes were prepared by dip coating a fibre glass sleeve in a PVDF solution, followed by precipitation via nonsolvent induced phase separation (NIPS) in 96% ethanol. The combination of these was optimized for obtaining membranes with a low-resistance thin polymeric layer and enhanced mechanical stability. The influence of both the withdrawal rate and the viscosity of the dope solution were investigated. The thickness of the PVDF coating layer was evaluated in the frame of the Landau-Levich model, which predicts that the film thickness results from the balance between viscous drag and surface tension forces. Among all the prepared membranes, the membranes prepared from a dope solution at 60 °C and with a withdrawal rate of 0.5 cm/s were selected to be used as support to grow biofilm for an application as Membrane Aerated Biological Reactor (MABR). The performance of the MABR, with the biofilm grown on the outer surface of the PVDF membranes and airflow supplied through the lumen of the fibre glass sleeve, was evaluated in terms of removal of Chemical Oxygen Demand (COD), ammoniacal nitrogen and total nitrogen. The MABR set up enabled the simultaneous abatement of the aforementioned parameters, with 78% of removal for COD, 21% for ammonia and 5% for total nitrogen, an interesting starting point for lab-made membranes exploited for this application.