C - Chemistry – Metallurgy – 02 – F
Patent
C - Chemistry, Metallurgy
02
F
C02F 1/52 (2006.01) C02F 1/62 (2006.01) C02F 1/70 (2006.01) C02F 9/00 (2006.01)
Patent
CA 2079632
A process for precipitating and removing chromium compounds in which chromium is in the hexavalent state from aqueous liquids, particularly, alkaline earth metal or alkali metal chlorate-rich solutions containing chloride, chlorate, andbichromate produced by the electrolysis of brine. In the process,hydroxylamine, hydroxylamine sulfate, hyroxylamine formate or hydroxylamine hydrochloride is used as a reducing agent to react and co-precipitate at a neutral or acid pH with hexavalent chromium ions present in the aqueous liquid, the reaction and precipitation taking place, generally, at a pH of about 4.0 to about 6.5 and, a temperature of about 50°C to about 100°C. Precipitated oxides and hydroxides of divalent and trivalent chromium can be removed, for instance, by filtration. Reaction time to achieve a level of about 10 parts per million or less of chromium ions in the filtrate varies from less than about 5 hours to less than about 1 hour depending upon selection of reaction temperature and reaction pH. For instance to achieve a level of 2 parts per million or less chromium ion after removal of the precipitate formed during the reaction at a pH of 5.0 - 5.5, a reaction time of 10 minutes at a temperature of 90° - 95° C is required. A reaction time of 30 minutes at a temperature of 70° C or 120 minutes at a temperature of 60° C provides a similar level of chromium ion removal.
Jackson John Robert
Pitzer Charles L.
Gowling Lafleur Henderson Llp
Huron Tech Corp.
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