Tannic-membrane interactions on ultrafiltration of cork processing wastewaters

Cork processing wastewaters are very complex mixtures of vegetal extracts a nd have, among other natural compounds. a very high content or phenolic/tan nic colloidal matter, that is responsible for severe problems of membrane f ouling and drastic Flux decline. In the present work the identification and quantification of phenolic/tannic compounds, responsible for membrane foul ing, is carried out through the use of reverse phase high pressure liquid c hromatography (HPLC). The compounds studied were gallic acid, protocatechui c acid, vanillic acid, syringic acid, ferulic acid and ellagic acid. The ve ry different characteristics of these compounds in terms of hydrophilicity/ hydrophobicity were correlated to their rejection coefficients for two cell ulose acetate ultrafiltration membranes of 6000- and 98000-Da molecular wei ght cut-off (MWCO). The ultrafiltration transmembrane pressures ranged from 0.5 to 4 bar and the feed flowrate from 100 to 200 1/h. The more hydrophob ic component (the ellagic acid) is almost totally retained and that indepen dently of the membrane MWCO, transmembrane pressure, and feed flowrate lead ing to the conclusion of formation of an adsorption layer responsible for m embrane fouling. (C) 2001 Elsevier Science B.V. All rights reserved.