Process and plant for reprocessing or concentration of used surfactant-containing iron phosphatising baths

摘要

A process and a plant (40) are specified for reprocessing or concentration of used surfactant-containing iron phosphatising baths, the used bath liquid being preclarified and then subjected to an ultrafiltration which is set so that the surfactants are predominantly retained as the retentate. Surfactants and if appropriate other additives can then be again supplied to the retentate via the lines (69, 70) in order to obtain an iron phosphatising bath (72) which can be used again. Preferably, a three-phase decanter (50) is used for the preclarification which permits a particularly effective separation of oil and sludge. The plant can also advantageously be made to be mobile in order to permit reprocessing of the used iron phosphatising baths with low capital costs for a relatively large number of smaller pretreatment plants (Fig. 2). <IMAGE>