| abstract |
Brine is purified prior to electrolysis by dividing it into two streams, removing sulfate from one of the streams by precipitation with calcium chloride to form calcium sulfate, removing the precipitate and re-combining the streams. Alkali hydroxide plus sodium carbonate are added to the re-combined streams to precipitate calcium carbonate which is removed. Any magnesium comes down as the hydroxide. The brine is then pure enough for electrolysis The calcium sulfate first precipitate is reacted with sodium hydroxide and carbon dioxide to form calcium carbonate which is then reacted with hydrochloric acid to form calcium chloride which is recycled to the process for precipitating calcium sulfate. |