Abstract: A method and a device for the regeneration of an electroless metal deposition bath containing hypophosphite ions by electrodialysis is described. The method according to the invention and the device differ from the prior art in that the bath solution is led simultaneously through diluate compartments in a second electrodialysis unit having cathodes and anodes, which compartments are separated from concentrate compartments in the second electrodialysis unit on the cathode side by monoselective anion-exchange membranes and on the anode side by anion-exchange membranes, the diluate compartments and the concentrate compartments in the second electrodialysis unit being disposed alternately to one another.

Abstract: The filling of a filter for removing contaminants from air and other fluid is constituted by hanging freely-moving foil strips coated with active carbon and provided with a microorganism culture for biodegradation of the contaminants. Excess culture and detritus from the biodegradation fall out of the filling as the fluid passes downwardly therethrough.