The role of sodium metabisulfite in the treatment of chromium-containing wastewater

Use sodium metabisulfite to treat chromium-containing wastewater, reduce hexavalent chromium to trivalent chromium, and then precipitate. This agent has a reducing effect under acidic conditions, but does not have the effect of removing heavy metals. Because flake sodium sulfide also has reducing properties, it can effectively remove heavy metal ions. When used under alkaline conditions, it can form sulfide precipitation with heavy metal ions in wastewater to achieve the purpose of removal. When using sodium sulfide and sodium metabisulfite to treat hexavalent chromium-containing wastewater, sodium metabisulfite can be added first. After sufficient reduction reaction, the alkali is adjusted and polyaluminum chloride or polymeric ferric sulfate flocculant is added. Finally, sodium sulfide is added to remove unfinished precipitation. of heavy metal.

1. Pretreatment of sedimentation tank

Through natural sedimentation or centrifugal sedimentation, the metal residue in the electroplating wastewater is precipitated to facilitate the next step of treatment.

2. Comprehensive wastewater reaction tank

The main chromium element in the wastewater is precipitated by adding chemicals (such as adding heavy metal capture agents).

3. Settlement of inclined plate settlement plate

Metal ions mostly exist in the form of flocs in the solution. Therefore, the solution needs to be settled through an inclined plate settling plate.

4. Filter filtration treatment

After the inclined plate settling treatment, there is still a small amount of flocculent precipitate mixed in the solution. At this time, the solution needs to be transported to a valveless filter for filtration.