Electrochemical characterization of binder effect in natural magnetite electrodes for fluoride removal of well water

This work presents the study of the behavior of magnetite in fluoride electroadsorption. A concern in the fluoride electroadsorption is related to the type of binder, fluoride concentration, pH, and coexisting ions. A graphite/Nafion/magnetite electrode increases the specific capacitance of the surface favoring the surface complexation of anions due to the increase in the effective adsorption surface in this system. There is a tendency to increase the specific capacitance when the concentration and pH increase. The anionic affinity of the system is directly related to the nature of the ions and the hydrated ionic radius, in ions with the same charge, a lower hydrated radius results in a greater possibility of surface complexation. Excess OH− groups increase the accumulation of charge in the double layer, making the surface complexation of the anionic species towards the surface difficult. The selectivity trend is: CO32− > SO42− > F− > Cl− > NO3−. [Display omitted] •Natural magnetite presents good electrochemical properties for fluoride removal.•Nafion binder favors the effective surface area of magnetite for fluoride adsorption.•At 0.3 V, anion adsorption is favored by the anodic polarization of the electrode.•When pH increases, the excess of OH− hinders the complexation of anionic species.•The selectivity trend is given as: CO32− > SO42− > F− > Cl− > NO3−.