Process for treating waste pickling baths containing metallic salts and acids

• Main Authors: KAUNE, ALBERT, POETZSCHKE, MANFRED, BRUECKEN, VOLKER, WALLIS, ERNST
• Format: Patent
• Language: English
• Published: 30.11.1995
• Edition: 6
• Subjects: APPARATUS THEREFOR; CHEMICAL SURFACE TREATMENT; CHEMISTRY; CLEANING OR DEGREASING OF METALLIC MATERIAL BY CHEMICALMETHODS OTHER THAN ELECTROLYSIS; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; METALLURGY; PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY ORREFINING OF METALS; TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE

A spent liquor used for surface treatment of rolled steel products and contg. HF, HNO3, and salts of Fe, Co, Ni etc is worked up and recycled. In this method a cyclic scheme of acid dialysis, membrane electrolysis and evapn. takes place. In the acid dialysis a vol. of spent liquor per unit ion exchange membrane surface area of 0.5-10 1/hr./m2 is used, whilst in the membrane electrolysis a cathode potential of -400 to -1000mVh is employed which corresponds to a cell voltage of 2.8 to 5.0V. In the electrolysis, the catholyte used is the free acid of the depleted spent liquor, the anolyte is up to 1% HF/HNO3 and the freely selected cathode potential is kept at a constant level above a reference electrode by a rectifier.