Review of sources and comprehensive treatment technologies for fluoride-containing wastewater from typical industries

Fluorine is a highly reactive and widely distributed element. Although fluorine is a trace element necessary for the human body, exposure to substances with high fluorine content can be harmful to both flora, fauna, and human health, leading to issues such as dental fluorosis, skeletal fluorosis, neurologic disorder, and disruption of ecosystem balance. The sources of fluorine emissions in key industrial sectors, their environmental impacts, as well as the technologies and methods for fluoride removal in fluoride-containing wastewater are explored successively in this paper. An analysis of the characteristics and challenges in treating fluoride-containing wastewater is provided insight into advancing ecological environmental protection and safeguarding human health. The characteristics of fluorine pollution and its ecological impacts, summarizing the sources, production characteristics, and environmental effects of fluoride-containing wastewater are briefly introduced in traditional industries such as phosphate fertilizer production, hydrofluoric acid manufacturing, steel smelting, and aluminum electrolysis. The generation processes and characteristics of fluoride-containing products are also discussed in new industries, such as photovoltaics, lithium batteries, graphite purification, and semiconductors during precision processing or advanced manufacturing. To address these issues, five common fluoride removal technologies: chemical precipitation, coagulation precipitation, adsorption, fluidized bed crystallization and ion exchange/membrane separation are reviewed in terms of their development status, fluoride removal efficiency, and application characteristics. Chemical precipitation is widely used in industrial applications for high-concentration fluoride wastewater, but a large amount of sludge is generated, which can cause secondary pollution. It requires coagulants and is often combined with coagulation precipitation to achieve satisfactory results. Adsorption is highly effective and widely applied for treating low-concentration wastewater, but attention must be given to the selection of adsorbents and the impact of coexisting ions. New technologies such as fluidized bed crystallization and membrane separation can be offered more efficient fluoride removal but are costly and often more suited for low-concentration wastewater. Challenges will be remained in the adaptability and safety of fluoride removal processes, the broad applicability and efficiency of fluoride removal reagents, and the regeneration and economic viability of these methods. Selecting appropriate treatment methods and reagents based on the characteristics of fluoride-containing wastewater will enhance fluoride control technologies and promote environmental sustainability.