Wet classification behavior of bidisperse colloidal particles through nanofibrous membrane

Abstract

Membrane separation has emerged as a prominent method for the removal of undesirable particles from wastewater in the field of water treatment. However, classification of particles with varying sizes by membrane is still poorly understood, warranting further exploration. This study is to investigate the wet classification behaviors of polydisperse particles using a nanofibrous membrane that features a complex three-dimensional network structure and high porosity. The experimental results demonstrate that the nanofibrous membrane is effective in retaining larger particles, while its high porosity facilitates the smooth passage of smaller particles. To clarify the classification mechanism, we analyzed the filtration model and employed SEM images taken at different stages of the process to investigate the retention behavior of larger particles. The filtration of larger particles through microfiltration membrane exhibited a cake filtration model. The blockage of large particles on the membrane surface formed a cake layer, significantly reducing the filtration rate. Conversely, the nanofibrous membrane exhibited continuous intermediate blocking filtration at pH 11, resulting in effective retention of larger particles inside the membrane rather than solely on membrane surface. This enabled better utilization of the pore space within the nanofibrous membrane, thus highlighting it as a potential area for future research.