As a water treatment agent, ferric chloride, ferrous sulfate and polymerized ferric sulfate are Coagulants of ferric salt series, which have good flocculation effect in wastewater treatment. Ferric chloride generally has two forms: liquid and solid.

Ferric chloride is easy to dissolve in water. After dissolving in water, it will hydrolyze and combine with hydroxyl ion in water to form ferric hydroxide colloid. Ferric hydroxide colloid will combine with suspended solids in water to form precipitation, so it has good water purification effect. Ferric chloride has good decolorization, deodorization, sterilization effect, and is widely used. In daily life, solid ferric chloride is more common. The iron ion formed after hydrolysis has strong oxidizability and can replace heavy metal ions in water, such as copper and iron, so it is widely used in metal industry. The cost of ferric chloride with the same concentration is about 40% less than that of polyaluminum chloride, and it can be used as a substitute in some places. Compared with other flocculants, liquid ferric chloride saves a lot of dissolving equipment and avoids the incomplete dissolving problem. The flocculation effect is better. Because ferric chloride does not contain some ions harmful to human body, its treated water quality will be better.