Water Treatment Chemicals Ferric Chloride

1. Traits

Ferric chloride is an ionic compound, also known as ferric chloride. The chemical formula is FeCl3, and the relative molecular mass is 162.21. Anhydrous ferric chloride has a hexagonal dark flake structure with metallic luster. Red in projected light, green in refracted light, sometimes light brown to dark in color (see Figure 4-5). The density is 2.898 g/cm3, the melting point is 304°C, and the boiling point is 323°C. Soluble in water, ethanol, glycerin, ether, acetone, hardly soluble in benzene. Ferric chloride has strong hygroscopicity and can absorb moisture in the air and deliquesce. Its aqueous solution is acidic and highly corrosive. Its hydrate is ferric chloride hexahydrate (FeCl?·6H2O), orange crystal, easy to absorb water, and has a pungent HCl odor. The liquid product is reddish brown.

2. Mechanism of action

Ferric salts act as trivalent aluminum salts and also form hydrated mononuclear complexes. The density and strength of the alum flowers formed by the iron salt are relatively high, and the water purification effect is remarkable. The hydrolyzed product of iron salt can be used as a coagulant. It is a positively charged hydrated mononuclear ion and polynuclear ion complex, which will adsorb negatively charged colloidal ions.

3. Purpose

The largest application field of ferric chloride is the water treatment sector, and its dilute solution is used as a flocculant and precipitant in water treatment to treat domestic water, industrial water, municipal sewage, and industrial wastewater. The water purification effect of ferric chloride is less affected by the water temperature and pH, the price is cheap, and it has a better treatment effect on some raw water (such as hard water). Its treatment effect on domestic sewage and industrial wastewater is also very good, because it can not only precipitate heavy metals and sulfur compounds in sewage or wastewater, but also form Fe(OH)?alum flowers that are difficult to degrade in water. Impurities such as polymers are adsorbed and removed, and the phosphorus content in the treated water is also greatly reduced.

4. How to use

Liquid products are directly metered and added. The solid product is first formulated into a 10% to 20% solution in the dissolution tank and then metered and added. The amount used to treat industrial wastewater can be determined through experiments. The solid product is highly hygroscopic, and it is best to make a solution at one time after unpacking. The effective dosage concentration of the product is generally 10-50 mg/L. When the alkalinity of the water is low or the dosage is large, an appropriate amount of lime should be added to the water to increase the alkalinity.

5. Precautions

Ferric chloride is highly corrosive, and the dosing equipment needs to be treated with anticorrosion, and the operators should be equipped with labor protection facilities. Ferric chloride should be stored in a cool, dry and ventilated warehouse, and should be protected from rain, collision and pollution by toxic substances. It is not suitable to be stacked in the open air.