Abstract: The present invention is directed to a process for removing and optionally recovering hexavalent chromium from chromium waste water. The invention involves the use of a treatment mixture comprising the combination of barium carbonate and/or barium hydrate, plus one or more certain specified acetates. The process involves contacting the chrome waste water to be treated with the treatment mixture at an acetic pH not exceeding 6.0, and usually from 4.0 to 6.0, followed by filtration through an acid-resistant filter. The chromium removed by this filter in the form of barium chromate can be regenerated into chromic acid by backwashing the filter into an agitated tank and treating to produce chromic acid and barium sulfate. The thus-generated chromic acid can then be returned to the chrome plating tank for reuse after passing through a filter to remove the barium sulfate.

Abstract: The present invention is directed to a process for removing and optionally recovering hexavalent chromium from chromium waste water. The invention involves the use of a treatment mixture comprising the combination of barium carbonate and/or barium hydrate, plus one or more certain specified acetates. The process involves contacting the chrome waster water to be treated with the treatment mixture at an acetic pH not exceeding 6.0, and usually from 4.0 to 6.0, followed by filtration through an acid-resistant filter. The chromium removed by this filter in the form of barium chromate can be regenerated into chromic acid by backwashing the filter into an agitated tank and treating to produce chromic acid and barium sulfate. The thus-generated chromic acid can then be returned to the chrome plating tank for reuse after passing through a filter to remove the barium sulfate.

Abstract: The present disclosure is directed to a process for removing and recovering chromium from waste water in the form of chromic acid and/or metallic chromate salts by the direct precipitation of chromium using barium carbonate in aqueous solutions acidified with glacial acetic acid at an acidic pH preferably ranging from 4.5 to 4.7 followed by filtering the resultant chromium material with an acid resistant filter media having openings preferably in the 2 to 4 micron size range and acid-resistant within the pH range of 2 to approximately 5. The weight ratio of barium carbonate to chromium material contained in the waste liquid is preferably 2:1 and the preferable weight ratio of the barium carbonate to the acetic acid is preferably 3:1. The barium carbonate and acetic acid are freshly mixed in aqueous media prior to either addition to the chromium waste liquid or addition of the chromium waste liquid to the freshly prepared treating material in aqueous media.