The phosphorus removal principle of polymeric ferric sulfate

Polyferric sulfate (PFS), as an efficient phosphorus removal agent, has been widely used in the field of wastewater treatment. The phosphorus removal mechanism is mainly based on its chemical reaction with phosphate ions, which forms insoluble iron phosphorus compounds, effectively removing phosphates from water and preventing eutrophication of the water.

1、 Principle of phosphorus removal

The core principle of polymeric ferric sulfate phosphorus removal is to use its chemical properties to react with phosphate ions. When polymeric ferric sulfate is added to water containing phosphate, the dissolved trivalent iron ions quickly combine with phosphate ions to form insoluble iron phosphate precipitates. These sediments will then settle to the bottom of the water, effectively removing phosphate ions from the water through precipitation separation.

2、 Reaction process

Dissolution and hydrolysis: After the polymeric ferric sulfate is dissolved in water, the iron salt undergoes hydrolysis and polymerization reactions upon water absorption, resulting in the formation of a multi nuclear hydroxy complex with a relatively long linear structure.

Reaction and precipitation: These iron containing hydroxy complexes react with phosphate ions to form insoluble iron phosphate precipitates. At the same time, these complexes can effectively reduce or eliminate the zeta potential of colloids in water. Through electric neutralization, adsorption bridging, and the sweeping effect of flocs, colloids can condense, further promoting the precipitation of phosphates.

Precipitation separation: The condensed iron phosphate precipitate will be removed from the water body through precipitation separation, thereby achieving the effect of phosphorus removal.

3、 Influencing factors

The phosphorus removal efficiency of polymeric ferric sulfate is influenced by various factors, including:

Dosage: The size of the dosage directly affects the phosphorus removal effect. Insufficient dosage may lead to incomplete phosphorus removal, while excessive dosage may increase treatment costs. Therefore, the optimal dosage needs to be determined based on the content and type of phosphorus in the raw water, as well as the size of the designed effluent phosphorus content.

PH value: pH value has a significant impact on the phosphorus removal efficiency of polymeric ferric sulfate. Under neutral or slightly acidic conditions, the phosphorus removal effect of polymeric ferric sulfate is usually better. Therefore, it is necessary to adjust the pH value of the water body before treatment.

Water temperature: Water temperature can also affect the phosphorus removal efficiency of polymeric ferric sulfate. Generally speaking, the higher the water temperature, the faster the chemical reaction rate, and the better the phosphorus removal effect. However, excessively high water temperature may also cause instability of sediment, affecting phosphorus removal efficiency.

Stirring and mixing: Adequate stirring and mixing can ensure that polymeric ferric sulfate fully contacts and reacts with phosphates in the water, thereby improving phosphorus removal efficiency.

4、 Application scope

Polymeric ferric sulfate can be used as a phosphorus removal agent for the purification treatment of urban drinking water and industrial circulating water, as well as for the purification treatment of industrial wastewater and urban domestic sewage in industries such as chemical, petroleum, mining, papermaking, printing and dyeing, brewing, steel, coal gasification, painting, leather, pharmaceuticals, food, electroplating, etc.

In summary, polymeric ferric sulfate forms insoluble iron phosphorus compounds through its chemical reaction with phosphate ions, achieving effective removal of phosphates from water. In practical applications, it is necessary to determine the dosage and treatment method of polymeric ferric sulfate reasonably based on factors such as the chemical properties, pH value, water temperature, and treatment requirements of the water body, in order to ensure the best phosphorus removal effect.