Immobilization of laccase from Trametes versicolor on a modified PVDF microfiltration membrane: characterization of the grafted support and application in removing a phenylurea pesticide in wastewater

Laccase immobilization onto a hydrophilic PVDF microfiltration membrane and its application for removing a herbicide derivative, N',N'-(dimethyl)-N-(2 -hydroxyphenyl)urea (2-HF), from waste water were studied. 2-HF was transfo rmed via an oxidation reaction catalyzed by laccase mostly into an insolubl e product, which was simultaneously separated by filtration through the mem brane. The microfiltration membrane used to graft laccase was treated with hydrazine to form a hydrazide group on its surface, which further reacts wi th the oxidized carbohydrate groups of the enzyme, leading to a covalent im mobilization of laccase. Contact angle measurements by the sessile drop tec hnique and X-Ray photoelectron spectroscopy followed the successive modific ations of the membrane. Streaming potential measurements as a function of t he pH led to determine the IEP of the grafted membrane at 4.1 +/- 0.5. This value is representative of the IEP of the laccase mixture produced by the white rot fungus Trametes versicolor. 2-HF removal experiments were perform ed in a microfiltration module. The performance of the laccase grafted memb rane was evaluated for different enzyme loading rates. It was shown that la ccase grafted membrane with a 60 cm(2) effective microfiltration area trans formed 200 mi of a 2-HF 0.1 g/l solution within less than 5 min. The main t ransformation product, an insoluble dark purple precipitate, was retained b y the membrane. (C) 2000 Elsevier Science B.V. All rights reserved.