Used primarily in water treatment as a coagulant to remove suspended particles and impurities. It helps clarify drinking water and treat wastewater by forming flocs that trap dirt, bacteria, and other contaminants. Also applied in paper manufacturing to improve ink and filler retention during the production process. In soil treatment, it can lower pH in alkaline soils, making them more suitable for certain plants. Additionally, it serves as a mordant in textile dyeing to fix colors on fabrics.