Neutralization of Ferrous Iron-containing Acid Wastes.
U S Pat 3 617 562 1971 Nov; :
Fe2+-containing waste waters, from pickling operations or mine drainage, are effectively cleaned up of heavy metals, giving an effluent with a ph >6, by neutralizing with a limestone slurry and then air stripping to remove co2 from the neutralized solution. Prior to the neutralization the fe2+ to fe3+ ratio in the waste water is adjusted to that in fe3o4 by a catalytic oxidation. A mixed valence sludge of higher density is precipitated and the better settling characteristics of the precipitate requires lesser amounts of limestone neutralizer; use of a slight excess of limestone (2-10 pct) is recommended for best results.
U.S. Pat. 3,617,562; Nov. 2, 1971; Chem. Abstr. 76:27,827F