Predictive membrane transport model for nanofiltration processes in water treatment

Authors

  • Shih-Chieh Tu,

    1. Dept. of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089
    Search for more papers by this author
  • Varadarajan Ravindran,

    1. Dept. of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089
    Search for more papers by this author
  • Walter Den,

    1. Dept. of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089
    Search for more papers by this author
  • Massoud Pirbazari

    Corresponding author
    1. Dept. of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089
    • Dept. of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089
    Search for more papers by this author

Abstract

A membrane transport model was developed for prediction and simulation of membrane filtration (nanofiltration) dynamics with reference to permeate flux. It incorporates important phenomenological aspects of membrane transport, such as concentration polarization and gel layer formation, and illustrates the concentration of solutes as foulants in the mass-transfer boundary layer on the membrane surface. Membrane filtration tests using tannic acid as a model organic compound were designed for investigating permeate fluxes, as well as solute concentration profiles for permeates and concentrates. Membrane performance experiments were conducted under various operation conditions by varying several parameters including solute concentrations, transmembrane pressures, and reject flow rates. The tests showed that the NF-45 membrane composed of polypiperazine amide was more susceptible to organic fouling by tannic acid than the NF-70 membrane made of cross-linked aromatic polyamide. These observations were supported by surface-potential measurements that demonstrated higher negative surface charges and greater hydrophilicity for the NF-70 membrane in the presence of tannic acid. The predictive capability of the membrane transport model was evaluated using the results from membrane filtration tests. Model sensitivity studies were conducted to obtain information on effects of various input parameters pertaining to operating conditions and fluid-dynamic regimes.

Ancillary