Flow Reversal and Pressure pulsation: Innovative technique to enhance flux in Nanofiltration

Abstract

Reduction in Permeate flux with the period of time is the major drawback for the Pressure-driven membrane processes. Concentration polarization and membrane fouling are the two major limitations for the Pressure-driven membrane filtration processes. They lead to the severe flux decline and that need to be controlled for the better process efficiency. The resistance determination provides basis for selection of membrane and appropriate pressure –driven separation process. This paper outlines a new approach for the flux enhancement by investigating the two techniques namely flow reversal and pressure pulsation. Resistance –in-series model was applied to quantify and describes the co-relation of the resistances taking into account the membrane hydraulic resistance as a base factor. It is also observed that membrane permeability decreases rapidly due to pore blocking and further declination of the flux is due to graduation accumulation of the foulant over the membrane surface. It is observed that membrane hydraulic resistance, R_m remained constant during the whole experiments while there is a reduction of concentration polarization (CP) resistance, R_cp in case of frequent flow reversal i.e from 52.08 to 35.50 %. However, in pressure pulsation technique not much flux variation was found during pressure pulse at different intervals.

Keywords: Nanofiltration; Flux; Resistance-in-series model; flow reversal; pressure pulsation.