The difference between polyferric sulfate and ferric sulfate

Polymeric ferric sulfate (PFS) is a high-molecular-weight coagulant widely used in wastewatertreatment. It is synthesized mainly from ferrous sulfate and sulfuric acid, and demonstrates superiorperformance in removing phosphorus, sulfur, SS, COD, and in bleaching applications compared tomany conventional coagulants.

Although both polymeric ferric sulfate and ordinary ferric sulfate are inorganic compoundscontaining trivalent iron ions, they differ significantly in structure and properties:

Molecular Structure

Polymeric ferric sulfate is a macromolecular polymer, whereas ferric sulfate is alow-molecular-weight inorganjic salt.Upon hydrolysis, PFS forms long-chain colloidal species withstrong adsorption and net-trapping capabilities, enhancing its coagulation efficiency. In contrast,ferric sulfate hydrolyzes to simpler, less effective species with weaker colloid-adsorption capacity,which is why it is seldom used as a primary coagulant in sewage treatment.Applications

Ferric sulfate is primarily employed as an analytical reagent, catalyst, or mordant in industries suchas medicine and fertilizer production. Its lower cost makes it suitable for certainnon-water-treatment roles. However, it tends to release more free trivalent iron ions, which can becorrosive.

Polymeric ferric sulfate, on the other hand, is specifically designed as a high-performance coagulantfor physicochemical treatment processes in wastewater. Its polymeric structure provides betterflocculation, wider pH adaptability, and less corrosiveness compared to the conventional ferricsulfate.