Electrodialytic Recovery of Sulfuric Acid and Iron Content from Spent Pickling Liquor
Historically, attempts to apply electrodialysis to the recovery of sulfuric acid from spent pickling liquor go back to the early fiftys, at a time when the first reasonably stable, synthetic ion exchange membranes became available. Thus H. C. Bramer and J. Coull of the Mellon Institute and C. Horner and G. IV. Bodamer of Rohm Haas disclosed within the same year (1955) in Industrial Engineering Chemistry (Vol. 47) two independent investigations of the feasibility of such recovery; the latter pair of researchers were awarded a patent for their particular approach (U.S. Patent 2,810,686(1957) While some differences in flow pattern through these early cells were indicated, each functioned on the electrodialytic displacement of sulfate ion into an anode chamber across an anion permselective membrane, until the concentration of free acid had diminished to a level which permits the cathodic reduction of FeII to elemental iron and the growth of spongy or dense or dendritic deposits of the metal on the cathode. Both featured dependence on the electrolytic decomposition of water at the anode to supply hydronium ion to complement the incoming sulfate ions, so that in effect the acid is reconstituted in the anode leg of the system.
KeywordsFerrous Sulfate Anode Chamber Feed Line Cation Exchange Membrane Anion Exchange Membrane
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