Used as a coagulant in water and wastewater treatment to remove suspended solids, phosphates, and heavy metals. It helps clarify water by forming flocs that settle easily. Commonly applied in sewage treatment plants and industrial water treatment systems. Acts as an etchant in the production of printed circuit boards (PCBs), where it dissolves copper from copper-clad laminates to create precise circuit patterns. Employed in the chemical synthesis industry as a catalyst or reagent, especially in organic reactions such as Friedel-Crafts reactions and chlorination processes. Utilized in the leather tanning industry to treat hides and improve dye absorption. Also used in pigment production and as a disinfectant in some municipal sanitation applications.