Recovery of chromium values from waste streams by the use of alk

Details Recovery of chromium values from waste streams by the use of alk Recovery of chromium values from waste streams by the use of alk

1977-04-18

1978-08-22

Hearn, Brian

Bleaching and dyeing; fluid treatment and chemical modification

Treatment of hides, skins, feathers and animal tissues

Tanning

106 59, 423 36, 423 43, 423106, 423109, 423146, 423 55, 423 57, 423592, 423597, 423150, C14C 306, C01G 3700

Patent

active

041085965

ABSTRACT:
A process and a product formed thereby for the recovery of chromium values from aqueous solutions (e.g., waste liquors) comprises contacting an acidic solution containing sulfate ion and trivalent chromium ion with at least about 4 molar equivalents of MgO or Mg(OH).sub.2 per 3 molar equivalents of trivalent chromium in addition to the amount required to neutralize the free acid to a pH of about 4 to form an amorphous, dense solid, grainy, easily settleable, trivalent chromium-containing precipitate in an alkaline solution according to the equation: 3Cr.sub.2 (SO.sub.4) + 8 MgO .fwdarw.Cr.sub.2 (OH).sub.4 SO.sub.4 .multidot. 4Cr(OH).sub.3 .multidot. 4H.sub.2 O + 8 MgSO.sub.4. The trivalent chromium-containing product can be readily separated from the water and is a useful source of chromium for subsequent processing. The water remaining after separation of the precipitate contains less than 0.5 mg/l chromium.

REFERENCES:
patent: 747255 (1903-12-01), Spence
patent: 2110187 (1938-03-01), Williams
patent: 2766101 (1956-09-01), Carosella et al.
patent: 3438724 (1969-04-01), Hartford et al.
Patterson, "Technology and Economics of Industrial Pollution Abatement", I.I.E.Q. Document No. 76/72 (1976), pp. 69-126.
Udy, M., Chromium VRI., Reinhold Pub. Corp., N.Y., 1956, pp. 175-197, 277-279; 331.
Finholt, "Chemistry of Some Hydrolyzed Cr(III) Polymers", Ph.D. Thesis, U. Cal. 1960.
Harenberg, et al., "Chrome Recovery", in Das Leder, 25 (17), 11/74, pp. 219-222.

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