FOULING OF CERAMIC MEMBRANE BY MILK-PROTEINS DURING MICROFILTRATION

Fouling of a ceramic membrane with nominal pore size of 0.2 mu m was m easured under static conditions (adsorption and interaction of milk co nstituents with membrane surface), and dynamic conditions (concentrati on polarisation and interaction of milk constituents with membrane int erior). Static fouling (Fs) by milk proteins showed a 0.26 mL/L declin e in water flux compared to the initial water flux. Fouling by casein micelles' adsorption was evident by scanning electron microscopy of th e membrane surface. Skim milk microfiltration under dynamic conditions during batch circulation decreased subsequent water flux by Fd=0.74 m L/L, compared to the initial water flux. Active sites of the membrane were silanized using glycidoxypropyltrimethoxysilane or 3-aminopropylt riethoxysilane. Static and dynamic fouling by skim milk after silaniza tion caused similar water flux declines by both silanization treatment s, not markedly improving the flux. Soaking the fouled membrane in ure a, 6 mol/L (pH 8.5) for 72 h, or in 50 g/L mercaptoethanol in urea, 6 mol/L for 24 h, or in 50 g/L guanidine chloride in urea, 6 mol/L for 2 4 h, or batch circulation using urea, 6 mol/L did not restore the orig inal water flux completely. The data suggest that proteins are not sol ely responsible for static and dynamic fouling and/or interaction of m ilk components with ceramic membrane surfaces.