Super-porous PVDF nanofibre membranes for efficient desalination of brackish water in membrane distillation applications

S.D. Mhlanga, L.N. Nthunya, N.P. Khumalo, A.R. Verliefde
University of South Africa,
South Africa

Keywords: membrane distillation, nanofibres, PVDF, super-hydrophobic, desalination

Summary:

Water scarcity is becoming a serious problem in Southern Africa. Recent draughts have called for exploitation of alternative sources of drinking water such as brackish and seawater. Membrane distillation is an efficient desalination process that is receiving enormous attention. However, this process is affected by wetting of membrane pores and the low porous nature of membranes, which lead to lower rate of water recovery. This study sought to address these problems by fabricating highly porous and super-hydrophobic polyvinylidene fluoride (PVDF) nanofibre membranes modified with organically functionalized silica (Si) nanoparticles (NPs). The highly porous nanofibre membranes were synthesized using an electrospinning technique. The membranes were found to be highly rough, strong, and porous as demonstrated on the atomic force microscopy, small angle X-ray scattering and porosity measurements. Addition of the organically modified Si NPs to the electrospinning solution resulted in the formation of super-hydrophobic membranes. These membranes were tested for their salt rejection and water fluxes. They were found to reject the salt ions from water at high efficiencies (> 99%) with water fluxes ranging from 55 – 64 litres per hour indicating their capacity to produce high purity water in large quantities.