What is the best precipitation PH of ferrous sulphate in water treatment?

Ferrous sulfate can be used as a reducing agent, decolorant agent, and it has a very good effect in remove auxiliary chemical phosphorus in wastewater. Ferrous sulfate has a strong reductive, but it needs in the alkaline environment to make full use of its oxidation and flocculation. What is the best precipitation PH of ferrous sulphate in water treatment?

 

1. When the solution pH> 7, the flocculation effect is obvious. The iron Fe2 + will oxidized to ferric iron Fe3 + after decomposed in water, and then occur the flocculation reaction. Fe3 + 4Fe (oH) 2 + 2H2O + O2--4Fe (OH)3. The ferric ions can react with various organic pollutants and dissolved phosphates in the wastewater to form alum precipitates, and destroy the chromogenic groups in the wastewater to achieve the effect of flocculation and decolorization.

 

2. In the PH range of 7-8, ferrous sulfate can be used to remove COD. Ferrous sulphate has ability of neutralization and destabilization for suspension of colloidal granular in waste water. And it reacted with water, created viscose of ferric hydroxide colloid which has a strong adsorption. When the COD is insoluble in water, it will go through electric and then flocculation, precipitate to form sludge together with the ferric hydroxide. The removal rate of this solution is up to 88%.

 

3. When the solution PH > 9, ferrous sulfate can be used as a bleaching agent. When the PH value reaches 8 or more, after hydrolyzed, ferrous sulphate is oxidized to form a multinuclear complex, making the dyestuffs of the colored suspended matter in the waste water are flocculation into the precipitate when it through the net. The decolorization rate of this solution can reach 92%. The PH value need to use alkali agents (such as lime) to change into alkali. Lime can not only adjust the PH value, but also play a role in flocculation and phosphorus removal.

 

It should be noted that: In the process of flocculation, with the increasing amount of ferrous sulphate, the solution alkalinity reduces, the lower flocculation effect will occur. Therefore, we often add with the alkali water treatment agent to keep the water in alkaline PH. Such as ferrous sulfate + lime for dyeing wastewater treatment or decolorization.