Membrane fouling in ultrafiltration of cork processing wastewaters (Reprinted from Advances in Environmental Research, vol 3, pg 539-549, 2000)

摘要

This work addresses the evaluation of membrane fouling in the ultrafiltration of cork processing wastewaters, which are rich in phenolic/tannic colloidal matter. The performance of a commercial membrane, TS60 (Ropur), and four cellulose acetate membranes covering a wide range of molecular weight cut-offs (MWCOs of 4-98 kDa) was investigated under varied operating conditions (hydrodynamics and transmembrane pressure). The film theory was used to correlate the mass transfer coefficient, k, with the resistance introduced by concentration polarization and the rejection coefficient, f', with the fouled membrane resistance. The results show that for the membrane with the lower MWCO, TS60, very high rejections (similar to 100%) of organic matter and very low fluxes were obtained while the cellulose acetate membranes yielded rejections from 50% to 90% and much higher fluxes. Among the CA membranes, the decrease in rejection of organic matter was not accompanied by a significant gain in the permeate fluxes due to greater fouling of the higher MWCO membranes. The ATR-FTIR spectra of used and non-used CA membranes were compared. The shift of the nu(OH) band to higher wavenumbers observed in the spectra of used membranes may be ascribed to the presence of fouling material in the pores of the membranes. For the TS60 membrane, mass transfer was found to be controlled by concentration polarization and for the CA membranes both concentration polarization and membrane surface adsorption acted as resistances to mass transfer. [References: 16]