Widely used as a coagulant in water and wastewater treatment to remove suspended solids, phosphates, and other impurities. It helps clarify water by forming flocs that settle easily. Commonly applied in municipal sewage treatment and industrial effluent processing. Used in etching copper-based materials in printed circuit board (PCB) manufacturing due to its ability to oxidize and dissolve metal layers. Acts as a catalyst in organic synthesis, particularly in chlorination and Friedel-Crafts reactions. Also employed in the production of other iron compounds and pigments. Applied in the oil industry for treating drilling fluids and controlling hydrogen sulfide levels. Additionally used in small-scale applications such as odor control in wastewater systems and as a disinfectant in certain sanitation processes.