Permeate flux hysteresis with transmembrane pressure in the gel controlling membrane filtration

The formation of the gel layer occurs during the clarification of any plant extract in membrane filtration processes. This study was aimed at investigate the impact of the increasing and decreasing transmembrane pressure cycle on the permeate flux of ultrafiltration (UF) and nanofiltration (NF) membranes when a clarified extract of olive mill solid wastes (OMSWs) is used as feed mixture. A hysteresis effect was observed for the selected membranes with molecular weight cut-off in the range 150 - 3,500 Da. This phenomenon was studied by using a combination of the classical filtration theories in the context of two component filtration. Further, the mathematical theory was categorised depending on the cut-off of the membrane, having separate physical scenarios. The proposed model can track both the flux and the permeate concentration profile within a reasonable accuracy, explaining the underlying physics of gel formation as well as the system behaviour.