Polyferric sulfate is a kind of inorganic polymer coagulant with superior performance. It is a light yellow amorphous powder solid, easily soluble in water, and its 10% (mass) aqueous solution is reddish brown transparent solution with hygroscopicity. Polyferric sulfate is widely used in the purification of drinking water, industrial water, various industrial wastewater, urban sewage, sludge dewatering and so on. Do you know the preparation methods of polyferric sulfate?

There are three methods to prepare PFS flocculant

First, raw materials are ferrous sulfate, sulfuric acid and catalyst. Different catalysts can form different manufacturing processes. The process method is to concentrate the sulfuric acid washing solution, adjust the ratio of acid and ferrous, add a certain amount of sodium nitrite in a closed pressure vessel, and then inject oxygen. Under constant temperature and constant ferrous stirring, polymerized ferric sulfate can be obtained by reaction.

Second, raw materials are FeSO4 and waste H2SO4, which are by-products of titanium dioxide plant. The production process is to determine the content of iron in FeSO4 · H2O, dehydrate it by hot air, cool air when it contains 1-2 crystals, and make it into oxidized material in the presence of oxidant. At this time, the waste sulfuric acid and curing agent are solidified, and the polyferric product has been formed after curing. The production process control is soi24 -: Fe2 + (mo1) = 1.30:1.45

Third, the raw materials are concentrated sulfuric acid and ferrous sulfate; the preparation process is that concentrated sulfuric acid is directly added to ferrous sulfate, and then appropriate amount of catalyst MnO2 (or 30% dilute acid is added to ferrous sulfate, and then catalyst NaNO2) is added, and then air is introduced for oxidation, hydrolysis and polymerization to prepare polyferric sulfate.

Characteristics of polyferric sulfate: polyferric sulfate can be divided into solid and liquid. The liquid is reddish brown viscous liquid; the solid is red or light yellow granular material which is easily soluble in water. The main characteristic of PFS is that a large number of [FE4 (H2O) 6], [Fe2 (H2O) 6], [Fe (OH) 2] and other polynuclear complexes are produced after the hydrolysis of PFS. Through adsorption, bridging and cross-linking, the colloidal particles in water can be condensed together. At the same time, a series of physical and chemical changes have taken place, which make them have strong electric neutralization ability, thus reducing the potential of micelles, breaking the stability of micelles, and promoting the rapid coagulation and precipitation of micelles; due to the low alkalization degree of PFS (10% - 13%), PFS is more cohesive than polyaluminum chloride; the generated flocs are large, and the settlement is fast. In addition, the relative density is small, the application effect in air flotation is better; the pH value is applicable to the range of light (4-11), except for Mn, it has good removal effect on other heavy metals; it has good removal effect on SS, COD, BOD, chroma and odor; it has better effect on precipitation with a certain amount of coagulant aid polyallylamide; it has demulsification function, so it has a certain effect on the removal of emulsified oil; the preparation process is simple and convenient It has the advantages of simple production, low price of raw materials, easy availability, low corrosiveness, less dosage of chemicals and less sludge generation than other chemicals.