Review of fluorine removal methods from aqueous solutions

Abstract

Introduction. The high-quality water conditioning problem does not disappear from the agenda of chemists, biologists, and ecologists. Fluoride content is an important water quality indicator, as fluoride can have both positive and negative effects on the human body. The purpose of this work is a critical review of methods for removing fluorine compounds from natural surface and underground waters, and from wastewater. An analysis of 77 modern scientific articles was performed, the advantages and disadvantages of such methods as precipitation and co-precipitation, methods using semipermeable membranes, dialysis and electrocoagulation, ion exchange and sorption methods were determined.
 Results and discussion. It was determined that the precipitation and co-precipitation methods use of chemical reagents, so they are quite expensive, and the sediments formed in the defluoridation process are subject to disposal. Membrane methods do not require the chemicals addition, are highly efficient and easy to control, but at the same time, defluoridation removes other ions that are present in water and are important indicators of the drinking water quality. A significant disadvantage of membrane methods is that a major amount of brine is formed during the treatment process, which also creates a disposal problem. Dialysis and electrocoagulation methods have the advantages and disadvantages of electrochemical methods: they provide high quality water, but this is accompanied by increased electricity consumption, the use of limited service life electrodes. Along with the high degree of water defluoridation, ion exchange methods are characterized by high cost, as well as significant water consumption for such technological processes as loosening, regeneration and washing of ion-exchange resins. An additional problem is the flushing and rinsing wastewater disposal. Sorptive fluoride removal is the most promising and widely used method. The main advantages include the method simplicity, non-deficiency and availability of sorbents. Effective sorbents are natural minerals, foremost, clinoptilolite, nepheline, low-quality phosphorites and apatites, glauconite, basalt tuffs, which are abundant in the subsoil of Ukraine. Unlike other methods, the spent materials are easily disposed of, or can be used as additives in the production of silicate materials, for example, bricks.
 Conclusions. Promising fluoride removal methods are sorption methods using natural mineral and modified sorbents.