The influence of Mg2+ on the adsorption of fluoride by hydrous oxides in seawater

Abstract

Experiments demonstrate that F- adsorption in seawater is predominantly reversible and dependent on formation of MgF+ in solution and adsorption of free F- and co-adsorption of Mg2+ and F- at particle surfaces. At pH values where little free F- adsorbs without Mg2+ present (generally pH ≥ ZPC), F- adsorption by FeOOH, δMnO2, and SiO2.nH2O is greatly enhanced by the presence of Mg2+. The enhancement of F- adsorption correlates with the adsorption of Mg2+. At lower pH, where Mg2+ adsorption is minimal, F- adsorption is reduced in the presence of Mg2+ compared to Mg2+-free solutions. -from Authors