Removal of hexavalent chromium from waste material

Details Removal of hexavalent chromium from waste material Removal of hexavalent chromium from waste material

1991-07-15

1993-04-06

Hruskoci, Peter

Liquid purification or separation

Processes

Making an insoluble substance or accreting suspended...

210724, 210727, 210913, 423 55, C02F 162

Patent

active

052000885

ABSTRACT:
A method of removing Cr.sup.+6 from a solution is provided. In removing the Cr.sup.+6, an effective amount of an alkali metal dithionite is added to the solution to reduce substantially all of the Cr.sup.+6 to Cr.sup.+3. A soluble material is provided in the solution which will form a precipitate. Further, the soluble material is selected such that it will coprecipitate and tie up any dissolved or colloidal Cr.sup.+3 formed as a result of the reduction of the Cr.sup.+6. In one embodiment, the solution is alkaline and preferably, the pH of the solution is reduced sufficiently such that the soluble material will quickly precipitate and form the coprecipitate material with the Cr.sup.+3. Thereafter, the solution is filtered to remove the coprecipitated material from the solution and thereby form a supernatant solution suitable for waste discharge which has substantially lowered chromium values. The precipitate has the Cr.sup.+3 tied up in an insoluble non-leachable form.

REFERENCES:
patent: 3928195 (1975-12-01), Hoeltgen et al.
patent: 3981965 (1976-09-01), Gancy et al.
patent: 4259297 (1981-03-01), Kaczur et al.
patent: 4260491 (1981-04-01), Cassidy et al.
patent: 4671882 (1987-06-01), Douglas et al.
patent: 4704259 (1987-11-01), Lipsztajn
"Chromium (III) Hydrolysis Constants and Solubility of Chromium (III) Hydroxide" by Rai, et al., Inorganic Chemistry, vol. 26, 1987, pp. 345-349.

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