Effect of BSA and sodium alginate adsorption on decline of filtrate flux through polyethylene microfiltration membranes

Abstract

To demonstrate the impact of the interaction between fouling substances and membrane materials on the decline of filtrate flux quantitatively, we developed a novel experimental system consisting of (1) closed-loop cross-flow filtration tests to demonstrate the relationship between the concentration of fouling substances in the feed solution and the steady-state flux, which is a traditional evaluation approach, and (2) pure water flux tests with membranes that are immersed in solutions of the same fouling substances prior to the tests to demonstrate the effect of their adsorption on the membrane performance. Bovine serum albumin and sodium alginate were used as model substances for proteins and polysaccharides, respectively, and polyethylene microfiltration membranes were used. Interestingly, the fluxes in both experiments were comparable to each other when the concentration of the fouling substances and the initial flux were equal. Because the only factor to increase the filtration resistance in the second experiments was adsorption, which was not affected by the filtration conditions, the results directly proved that the adsorption of these substances on the membrane surfaces and pore walls was dominant in the reduction of filtrate fluxes, even though the extent of the reduction was not severer in the case of sodium alginate.