| 摘要 |
PURPOSE:The title reducing agent, capable of reducing hexavalent chromium in waste liquor into trivalent chromium Cr (III) and precipitating and separating Cr (III), obtained by freezing and thawing a finely divided slurry of ferrous hydroxide (F) to settle granular F, and by concentrating the slurry. CONSTITUTION:A ferrous salt, e.g. ferrous sulfate, is neutralized with an equivalent amount of an alkali hydroxide to form green precipitates of ferrous hydroxide. The resulting slurry is frozen in an airtight state to form ice crystals from the water in the slurry. The frozen slurry is then thawed at room temperature and washed with water to give a ferrous hydroxide slurry, which is added to a hexavalent chromium waste liquor to reduce the chromium to the trivalent chromium Cr (III). The treated liquor is led to a magnetic separation tank to separate and remove most of the chromium and iron ions, as a sludge. The remaining liquor is returned to the reducing tank and reused continuously. |
