Patent ID: 6379559
Filing Date: 2002-04-30
Classification: C02F,C25D,Y02W

Abstract:
A method of rendering sludge which sediments in a chromium plating impurity recovery electrolysis tank harmless, said method comprising:separating metal ions contained in chromium plating effluent or a mixed solution of chromium plating solution, chromium plating effluent and chromic acid wash water in an impurity recovery electrolysis tank in the form of a sludge which is extracted, washing said sludge with water until the amount of hexavalent chromium eluted from the sludge does not exceed 0.2 g/l, separating the wash water containing chromic acid and the sludge, drying said sludge which sedimented in the water washing, adding natural organic rice husks to said sludge, and reduction calcinating said sludge containing the natural organic substance under a reducing calcination temperature of between 900 and 1000Â° C., thereby rendering said sludge harmless with reproducibility.