Methods for Reducing Fluoride Ion Concentrations in Industrial Wastewater: Mechanisms, Performance, Limitations, and Implementation Perspectives

Industrial wastewater containing fluoride ions (F−) is characterized by substantial variability in composition, pH, salinity, and F− concentration, which makes it difficult to apply a single universal treatment technology. The aim of this article is to critically compare methods for reducing fluoride ion concentrations in industrial wastewater, with particular emphasis on chemical precipitation, coagulation/flocculation, electrocoagulation, adsorption, ion exchange, and membrane processes. The analysis focuses on process efficiency, initial and final fluoride concentration ranges, the effects of pH and coexisting ions, material regeneration, the generation of secondary waste, and the applicability of individual technologies to real industrial wastewater. The review indicates that precipitation using calcium-based compounds remains the primary method for reducing high fluoride concentrations, whereas adsorption, ion exchange, and membrane techniques are mainly employed as polishing steps. The key limitations of the current state of knowledge include the predominance of studies conducted using model solutions, limited data on real industrial wastewater, and insufficient assessment of treatment costs, sorbent regeneration, and the management of sludge and concentrates.