PHOSPHOLIPID COATINGS FOR THE PREVENTION OF MEMBRANE FOULING

The aim of the present work was the development of phosphorylcholine-b ased treatments for biofiltration membranes and the demonstration that such treatments prevent or inhibit protein fouling. Microfiltration m embranes of cellulose triacetate, polyether sulphone and polyvinyliden e fluoride were etched with oxygen in a plasma chamber to generate sur face hydroxyl groups and were then treated with the monomer 2-methacry loyloxyethyl phosphorylcholine. These membranes were evaluated with wa ter, buffer, bovine serum albumin (BSA), yeast fermentation broth, bee r and orange juice. The treatment of cellulose triacetate membranes re duced both the initial flux and the extent of water fouling. In terms of the integrated flux, these factors tended to cancel each other out. For protein, the membranes gave similar or higher fluxes but worse fo uling. The cellular feed (yeast) reacted more favourably to the coatin g than the BSA. The polyether sulphone was scarcely affected by the co ating; fouling remaining high with most 'real' feeds. There was lower initial flux but less flux decline with water and beer. Washing with w ater and cleaning with Tergazyme did not restore the initial flux. Pol yvinylidene fluoride membranes gave the most positive results. In most cases, the coating both increased initial flux and decreased the rate of fouling. The coating was particularly effective for BSA and for be er and orange juice, where fouling is probably caused by a polysacchar ide rather than by a protein. Electron microscopy showed, nonetheless, that fouling by proteins was accompanied by protein adsorption primar ily on the upper surface of the membrane and that coated membranes sho wed less deposition and in different places than did untreated membran es.