Collect. Czech. Chem. Commun. 1997, 62, 1413-1422

Determination of Limiting Flux and Threshold Pressure in Stirred Ultrafiltration of Colloidal Suspensions

Goran T. Vladisavljevic and Vladeta Lj. Pavasovic

Institute of Food Technology and Biochemistry, Faculty of Agriculture, Belgrade University, P.O.Box 127, 11081 Belgrade-Zemun, Yugoslavia


The stationary permeate flux during ultrafiltration of colloidal suspensions reaches a limiting value, Jl, at high pressure differences. According to the gel polarization model employed here, the existence of this limiting flux is a consequence of gelation of the solution at the membrane-solution interface. The limiting permeate flux, Jl, can easily be determined from experimental data by plotting ∆p/Js against ∆p. Furthermore, the membrane resistance at zero pressure difference, Rm0, and the pressure difference necessary to reach 95 per cent of the limiting flux, i.e. the threshold pressure, ∆pt, may be calculated, too. The agreement between the model and experimental data is satisfactory. The laboratory-made silica sol consisting of uniform spherical particles with a surface average diameter of 18 nm was selected as a working fluid throughout this study.

Keywords: Ultrafiltration; Limiting flux; Membrane resistance; Silica sol; Threshold pressure.