Centrifugal casting of ceramic membrane tubes and the coating with chitosan

In this paper, the centrifugal casting of ceramic membrane tubes is present ed using different powder particle sizes and powder mixtures. The inner sur face of the tubes has a very regular pore structure and is also very smooth . The strength of the tubes increases with increasing sintering temperature and decreasing particle size up to stress values of 1500 MPa. For the stro ngest materials, the pores sizes and porosities are in the order of 50 mn a nd 30%, respectively. The water permeability varies between 5 and 50 1/m(2) .h.bar, The inner surface of the tubes was coated with a highly porous chit osan biopolymer layer of 30-50 mum thickness, The chitosan layer is prepare d by a phase-inversion method using water with low and high pH values as a solvent/non-solvent system. Silica, which dissolves at high pH values, is u sed as porogen and creates the pores. This biopolymer can adsorb heavy meta ls like copper. With this membrane system, Cu2+ (50 ppm. as CuSO4) can be r emoved almost completely with a membrane capacity of 0.1 g Cu2+/g chitosan. (C) 2001 Elsevier Science B.V. All rights reserved.