Difference between polyferric sulfate and ferrous sulfate

The main differences between ferrous sulfate and polymeric ferric sulfate are reflected in chemical properties, treatment effects, application scenarios and environmental adaptability, as follows:

I. Chemical properties and structure

1.Chemical formula and iron ion valence state

● Ferrous sulfate: the chemical formula is FeSO₄·7H₂O, iron is divalent (Fe²⁺), belongs to low molecular inorganic compounds. It has reducing properties and can react with chromium hexavalent and other pollutants by REDOX reaction.
● Polyferric sulfate: The chemical formula is [Fe₂(OH)ₙ(SO₄)₃-ₙ/₂]ₘ, with iron in the trivalent state (Fe³⁺), it belongs to inorganic polymers. After hydrolysis, it forms multinuclear complexes (such as [Fe₂(OH)₄]²⁺), which remove pollutants through adsorption and electro-neutralization.

2.physical property

● Ferrous sulfate: light green or light yellow crystalline solid, easy to deliquesce, solution is light green; it needs to be in slightly alkaline (pH 8-10) conditions to achieve the best effect.
● Polyferric sulfate: yellowish brown or reddish brown powder/liquid, low solubility, but pH wide range of adaptation (4-11), especially suitable for low temperature, high turbidity water quality.

II. Application fields and processing effects

1.ferrisulfas

● Functional properties:
      ● It has both reducing properties (such as reducing hexavalent chromium to trivalent chromium), coagulation properties and decolorization properties.
     ● The decolorization effect is strong, and the wastewater of reactive dye can be nearly colorless after treatment.
● main application:
     ● Electroplating wastewater (treated with heavy metals such as chromium and copper).
      ● Agriculture (supplement iron), industrial fungicides.

2.Polyferric sulfate

● Functional properties:
      ● The removal rate of COD and BOD was 80% and 93% respectively by adsorption and net capture of multi-nuclear complex.
      ● The decolorization effect is slightly weaker than that of ferrous sulfate (94%-98% vs. nearly colorless), but it is more efficient for COD removal.
● main application:
      ● Water purification, Industrial Wastewater (dyeing, paper making, electroplating, etc.), sludge dewatering.
      ● Low temperature or high turbidity Water Treatment.

Cost and environmental impact

● Ferrous sulfate: low cost, but easy to oxidize and fail. Excessive use will lead to residual iron ions in water, which may cause secondary pollution.
● Polyferric sulfate: the dosage is only 20%-50% of ferrous sulfate, less sludge and easier to dehydrate, no aluminum and chlorine residue, better environmental protection.

Other differences

sum up

Ferrous sulfate is suitable for the treatment of reducing pollutants (such as hexavalent chromium) and low-cost scenarios, while polymeric ferric sulfate is more efficient and environmentally friendly, suitable for complex water purification. The actual choice should be combined with the type of pollutants, treatment requirements and cost budget.