Electrospun mat swelling: An ally to improve membrane rejection ratio

LAURA RIBBA; SILVIA GOYANES; JONATHAN CIMADORO; NANCY LIS GARCIA

Berlin

Congreso; 8th World Congress on Biopolymers & Bioplastics; 2018

Electrospun polymer fibers have been widely applied as filtration media. The meshes pore size, is usually estimated in literature from microscopy images. However, if the polymer undergoes a swelling process in the filtrated liquid this will change, causing differences in both the particle size it is able to retain and the permeation rate. In this work the effect of polymer swelling on electrospun PVA mats morphology when used as water filters is studied. Electrospun mats were employed to filter pure water during different times (0, 5, 10, 30 and 60 minutes), and observed immediately after that using an AFM. The average diameter of PVA fibers notoriously increases (about a 68%) with filtering time after a short transitory stage, evidencing the swelling process. This effect causes a decrease in the effective spaces between fibers, through which water can permeate. On the other hand, the RMS roughness of the meshes was calculated by the program NanoSurf C3000 over an area of 10 x 10 microns for each image taken. Again a strong change in this parameter is observed, showing a significant decrease in the roughness probably caused by the pressure produced by the water column and the swelling. It is interesting to study how the water permeated volume changes as a function of time during the first transitory stage. To evaluate this, the volume of water passing through the membrane was measured for 90 minutes. During a first stage the system goes through a transitory stage in which the flow at which the water permeates is diminishing. This result is consistent with both the increase in diameter and the change in mesh density.