Abstract
In this study, micellar-enhanced ultrafiltration (MEUF) was used to remove Cd2+ from synthetic wastewater using a polysulfone spiral wound ultrafiltration membrane and sodium dodecyl sulfate (SDS) as a surfactant. The effects of two important parameters related to membrane fouling in MEUF were investigated: transmembrane pressure (TMP) and feed concentration. The recycling of retentate to the feed tank, which led to continuous growth of SDS concentration, is investigated. The permeate flux and fouling resistance around the critical micelle concentration (CMC) showed that higher SDS concentrations did not always lead to more serious fouling, but fouling became more serious after the SDS concentration reached five times the CMC. With increasing TMP, the flux declined drastically as a result of particle aggregation and gel layer formation. However, the TMP was not always a good criterion of membrane fouling: in different phases, high TMP and low TMP values affected membrane fouling differently; a high TMP such as 0.25MPa resulted in low membrane fouling at the beginning of the MEUF because of the higher driving power; and a low TMP such as 0.05MPa caused more serious membrane fouling after stopping because of pore blocking.
► In MEUF, initial feed solutions play a similar role as backwashing. ► Initial feed concentrations near to but lower than CMC led to more serious fouling. ► Membrane fouling got more serious when SDS concentration reached 5 CMC. ► TMP was not always a good criterion of membrane fouling at the beginning. ► Larger driving force caused by high TMP would result in lower Rf in some degree.