Comparison of treatment effects of ferrous sulfate and sodium bisulfite
The process of electroplating production needs to be galvanized, and in the process of galvanized purification, basically the electroplating plant will use chromate, so the electroplating wastewater will produce a large number of chromium-containing wastewater due to chromium plating. The chromium in wastewater containing chromium contains hexavalent chromium, which is toxic and difficult to remove. Hexavalent chromium is usually converted to trivalent chromium and removed. For the removal of chrome-containing electroplating wastewater, chemical coagulation and precipitation are often used to remove it. Commonly used are ferrous sulfate and lime reduction precipitation method and sodium bisulfite and alkali reduction precipitation method.
1. ferrous sulfate and lime reduction precipitation method
Ferrous sulfate is a strong acid coagulant with strong oxidation-reducing properties. Ferrous sulfate can be directly reduced with hexavalent chromium after hydrolysis in wastewater, converting it into a part of trivalent chromium coagulation and precipitation, and then adding lime to adjust the pH value to about 8~9, so that it can help the coagulation reaction to generate chromium hydroxide precipitation, the removal effect of chromate can reach about 94%.
Ferrous sulfate plus lime coagulant reduction chromate precipitation has good effect on chromium removal and low cost. Secondly, there is no need to adjust the pH value before the addition of ferrous sulfate, and only need to add lime to adjust the pH value. However, due to the large amount of ferrous sulfate dosing also caused a large increase in iron mud, increasing the cost of sludge treatment.
2,.sodium bisulfite and alkali reduction precipitation method
Sodium bisulfite and alkali reduction precipitation chromate, the pH of the wastewater is adjusted to ≤2.0. Then sodium bisulfite is added to reduce chromate to trivalent chromium, and the waste water enters the comprehensive pool after the reduction is completed, the waste water is pumped to the regulating pool for adjustment, and the pH value is adjusted to about 10 by adding alkali nodes, and then the waste water is discharged to the sedimentation tank to precipitate chromate, and the removal rate can reach about 95%.
The method of sodium bisulfite and alkali reduction precipitation chromate is good for chromium removal, and its cost is relatively higher than ferrous sulfate, and the treatment reaction time is relatively longer, and the pH value needs to be adjusted with acid before treatment. However, compared with ferrous sulfate treatment, it basically does not produce too much sludge, greatly reducing the cost of sludge treatment, and the treated sludge can usually be reused.
Post time: Mar-07-2024
