Solid polymeric ferric sulfate has good coagulation and sedimentation effect and decolorization effect in various wastewater. After the hydrolysis of PFS, the polymer can neutralize and bridge with the particles in water by potential, and then adsorb and catch by net. It can react with the chromogenic groups in wastewater to form complex precipitation, so as to achieve the purpose of removing chromaticity (decolorization effect of PFS). But sometimes, after using PFS for coagulation, the wastewater turns red, and there is no color phenomenon at the final outlet.
Causes of wastewater reddening caused by polyferric sulfate
When the wastewater turns red after adding polyferric sulfate, the first problem is the quality of polyferric sulfate itself. If the quality of poly iron itself is unstable, it will cause too much or too little instability. It may cause the wastewater to turn yellow, red or even black, so in this case, the quality of PFS should be detected first.
The second reason is that polyferric sulfate contains ferric ion, which is red. When it dissolves, it will appear red when there are more ferric ions in water. This is why liquid polyferric sulfate is reddish brown. When it is mixed with pollutants in water, its alum will also be red in the process of flocculation and sedimentation. There is a material phenomenon here, that is, the refraction of light. This refraction of light will produce a visual reaction of the human body, thinking that water is red.
In the coagulation process of PFS, when the alum in water is filtered or precipitated, the water entering the back end will not produce color, because the liquid PFS is reddish brown. The premise is that the dosage of PFS is reasonable, otherwise it will cause the waste of chemicals and the increase of water color. The reason is that ferrous sulfate contains Fe2 + and polyferric sulfate contains Fe3 +. Excessive Fe3 + will make the wastewater red.