The Study On The Membrane Fouling Characteristics During Ultrafiltration Of Surface-active Substances And Hydraulic Flushing Method

Micellar-enhanced ultrafiltration (MEUF), a surfactant-combined ultrafiltrationprocess (surfactant micelle solubilization and electrostatic adsorption), the micelleswere rejected by ultrafiltration membrane and then achieve the goal of removingorganic matter and heavy metals. Compared with the traditional ultrafiltrationtechnology, micellar-enhanced ultrafiltration has its own advantages such as highremoval efficiency, low energy consumption, simple operation, high recoveryefficiency and low cost. One of the greatest problems in MEUF is membrane foulingwhich is mainly caused by concentration polarization, gel layer or cake formationcaused by the deposition of surfactant micelles on the membrane surface andsurfactant adsorption in the membrane interior. During ultrafiltration process, themembrane fouling can reduce membrane ability to remove contaminants, or worseleads to membrane life shortened.In this paper, anionic surfactant sodium dodecyl sulfate (SDS), which was usedin membrane separation as colloidal particles, influenced the membrane fouling, usingpolyether sulfone membrane with molecular weight cutoff (MWCO10000Dalton).This study investigated the effects of transmembrane pressure (TMP) and feedconcentration of SDS on membrane flux. It was found that the flux increased with theincrease of TMP, from30.20L/m2.h at0.05MPa to80.15L/m2.h at0.20MPa, however,the flux decreased with the increase of feed concentration of SDS, ranging fro m38.87L/m2.h at2mM to30.12L/m2.h at10mM; SDS rejection decreased with anincrease of operating pressure, ranging from79%at0.05MPa to53%at0.20MPa. Inaddition, membrane fouling resistance increased with the increase of TMP and feedconcentration of SDS. They were increased from1.84×1012m–1at0.05MPa to4.86×1012m-1at0.20MPa and from0.51×1012m–1at2mM to1.86×1012m–1at10mM, respectively. Membrane fouling gradually increased with the operation time.This paper presented that the lower TMP had a smaller effect on membrane fouling,and when SDS concentration was around the critical micelle concentration (CMC),lower permeate flux and higher additional membrane fouling resistance were obtainedThe effects of three kinds of hydraulic flushing methods on membrane permeateflux were investigated, including periodic forward flushing, periodic backwashing andforward flushing followed by backwashing, to find out the best membrane cleaningmethods. It was found that when the periodic combined flushing interval was10min, forward flushing and backwashing phase time were150s and90s, respectively, wasmore conductive to permeate flux recovery in this study.