Process for treating spent iron-containing chromium plating solution to remove iron values contained therein and regenerate the solution

摘要

Novel and improved process for the treatment of exhausted chromium-plating solutions or electrolytes wherein all chromium values contained in the exhausted chromium-plating electrolyte can be converted to a water-soluble chromium chromate complex compound through treatment with a chromium chromate complex compound-forming reagent and, at the same time, all iron values which are present in the exhausted electrolyte and have a detrimental influence on the chromium-plating operation are converted to ferric hydroxide which precipitates and is easily removable. The thus obtained aqueous chromium chromate complex compound solution can be, in one way, recycled to the chromium-plating system, as a souce of trivalent chromium which is necessary, in a small amount, for preparing a useful chromium-plating electrolyte or solution; or can be, in another way, employed as an anode electrolyte of a diaphragm electrolysis to produce a fresh chromium-plating electrolyte.