Method for the removal of chromium compounds from aqueous solutions
US5211853A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 31, 1992 |
| Grant date | May 18, 1993 |
| Priority date | — |
| Expiry date | Jul 31, 2012 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S210/913
- WIPO fieldEnvironmental technology
- WIPO sectorChemistry
Abstract
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, and bichromate ions produced by the electrolysis of brine. In the process, hydroxylamine, hydroxylamine sulfate, hydroxylamine 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.degree. C. to about 100.degree. 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, …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.