Study of the fouling of inorganic membranes by acidified milks using scanning electron microscopy and electrophoresis. I. Membrane with pore diameter 0·2 μm

Abstract

SummaryThe fouling of an inorganic microfiltration membrane with an average pore diameter of 0·2 μm obtained in static conditions with milk, acidified milk and acid coagulum was examined using scanning electron microscopy. The structure and porosity of external fouling related to the pH of the milk accounts for the performance and efficiency obtained in microfiltration. Electrophoretic analysis of permeate, characterized by lack of casein, shows that the deposit plays a fundamental role in mass transfer through filter layers. Variations in the physicochemical properties of casein as a function of pH at 50 °C were used to account for the development of the structure of fouling, which comprised three main states: (i) dense deposit of juxtaposed micelles, (ii) loose network formed by chains made up of bonded protein aggregate, (iii) irregular protein aggregate leading to high-porosity deposits. The presence of a protein film strongly adsorbed on the membrane layer of alumina particles is demonstrated.