화학공학소재연구정보센터
Journal of Membrane Science, Vol.255, No.1-2, 49-56, 2005
Effect of membrane pore size and solution chemistry on the ultrafiltration of humic substances solutions
Membrane fouling by humic substances is a major problem in ultrafiltration (UF) for drinking water production. This work addresses the effect of membrane pore size on the UF of model humic substances solutions with different chemical characteristics, namely pH and ionic strength. UF experiments are performed with cellulose acetate membranes covering a wide range of membrane pore sizes-20, 54, 62, 86 and 106 A-in laboratory flat-cell units of 13.2 x 10(-2) m(2) of membrane surface area and at transmembrane pressures varying from I to 4 bar. For the tighter membranes, there is a linear variation of fluxes in all the range of pressures and for all the humic substances solutions. The more permeable membranes display a non-linear variation of the fluxes as a function of pressure for all the humic substances solutions. In these membranes, with severe fouling characteristics, the permeation fluxes are lower when the ionic strength of the humic substance solutions increases. The membranes with pore sizes of 20, 54 and 62 A have rejection coefficients close to 100% for all the humic substances solutions. In contrast, the membranes with pore sizes of 86 and 106 A have lower rejections coefficients and they decrease when the ionic strength increases. The very different permeation patterns are correlated to the membrane pore size and to the solution ionic strength through the control of the mass transfer mechanisms, the humic macromolecules configuration and the membrane/humic macromolecules electrostatic interactions. The effect of ionic strength on humic acid deposition is enhanced in the more permeable membranes due to the higher contribution of convection to the permeation fluxes. © 2005 Elsevier B.V. All rights reserved.