Polyferric sulfate (PFS), also known as basic ferric sulfate or hydroxyl ferric sulfate, can generally be expressed as [Fe2 (OH) n (S04) 3 – N / 2] m . It is an intermediate product of ferric sulfate in the process of hydrolysis flocculation. Liquid Polyferric sulfate itself contains a large number of polymeric cations, such as [Fe3 (0h) 4] 5 +, [fe6 (OH) 12] 6 +, [FE4 (OH) 4] 6 +, and there are [Fe (H20) 6] 3 +, [Fe2 (H20) 3] 3 +, [Fe (H20) 2] 3 + in aqueous solution. As a new inorganic polymer flocculant, polyferric sulfate has the following advantages compared with traditional inorganic salt coagulants:
(1) Flocs (flocs) are formed quickly, the particles are dense, the ratio is large, and the sedimentation speed is fast.
(2) It has good removal effect on COD, BOD, chroma and heavy metals in various wastewater.
(3) Flocs (flocs) have strong binding ability with microorganisms, so they have a good removal effect on microorganisms such as plankton.
(4) In the application process, the raw water temperature and pH value have a wide range of adaptability.
(5) It can reduce the content of nitrite nitrogen and iron in effluent.
Because of its water purification performance, it is favored by the water treatment industry and has been widely used in various industrial wastewater and urban sewage treatment. Compared with traditional aluminum flocculants, PFS has no ionic water phase transfer and residual accumulation in the reaction process, which is more convenient to use, cheaper in price and less in dosage. However, the production of PFS by catalytic oxidation in industry has great pollution due to backward technology, simple equipment and so on. The results show that optimizing the preparation conditions and developing a low-cost production process of polyferric sulfate have a wide application prospect.