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Title: Effect of sodium alginate with calcium and alum on the flux and resistance of nanofiltration membrane
Authors: Wei, Chun.
Keywords: DRNTU::Engineering::Environmental engineering::Water treatment
Issue Date: 2009
Abstract: Nanofiltration (NF) is considered to be one of the typical membrane technologies and has received considerable attention in the recent years. However, the critical issues for the successful application of NF is membrane fouling, which would lead to the deterioration of the membrane performance. Extracellular polymeric substances (EPS) have been found to be one of the major fouling components in advanced wastewater reclamation. Thus, the commercial application of NF membrane on a cost-effect purpose requires a full understanding and exploration of the effect of EPS on the NF membrane performance as well as the fouling mechanism of EPS on the NF membrane. In this study, Sodium alginate, a hydrophilic microbial polysaccharide, used as the model compound representing the EPS was used in this study. Fouling experiments were carried out in a dead-end filtration apparatus, and the important parameters considered in the study were the concentrations of Ca2+ and alum which would have their influences on the fouling processes. Results obtained from filtering sodium alginate solution revealed their presence in feed water led to a serious decrease in NF permeate flux and high solutes rejection. It was found that cake filtration model appears to fit the entire range of the filtration of pure and Ca2+ added into sodium alginate solution while the combined pore blockage and cake filtration model was more applicable to the alum added sodium alginate solution fouling process: intermediate/complete pore blocking at the beginning of filtration, followed by cake development on the membrane surface. The cake formed by pure sodium alginate solution was found to be incompressible and with a large specific cake resistance value reflected the strong molecular foulant- membrane and foulant-foulant interactions. In the presence of Ca2+, the cake formed was also incompressible but smaller specific resistance value was obtained. This phenomenon would result from the complexation of sodium alginate with Ca2+ but the cake formed was more permeable. The cake formed by alum added solution presented a different characteristic that it was compressible and has a lowest specific cake resistance. Thus, sodium alginate was only adsorbed onto the aggregates formed by alum and this physical mechanism reduced the electrostatic repulsive forces among sodium alginate molecules as well as between the sodium alginate molecules and membrane surface.
Rights: Nanyang Technological University
Fulltext Permission: restricted
Fulltext Availability: With Fulltext
Appears in Collections:CEE Student Reports (FYP/IA/PA/PI)

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