3 is extracted hexavalent chromium from the chromium-containing waste water sludge method

摘要

PURPOSE: A method for extracting chrome from sludge is provided, which is characterized in that chrome ion in wastewater is restored by adding iron sulfate or iron chloride, and neutralized by calcium hydrate. CONSTITUTION: Iron sulfate or iron chloride is added to the wastewater so that chrome ions are restored, and neutralized by calcium hydrate. Then, sodium hydrate is added to maintain the pH of the sludge at 13 or more. Water is added to the neutralized sludge to form Na2Cr2O7. Treated sludge is filtered, and Na2Cr2O7 is separated from the sludge. Chrome hydrate does not react with iron hydrate or calcium sulfate in strong alkali condition, so after filtration, iron hydrate or calcium sulfate remains in the sludge, and only Na2Cr2O7 can be extracted, which can be reused for a source of a paint or pigment.