Removal of fluoride ions from aqueous solution using modified attapulgite as adsorbent

Adsorption of fluoride ions from water using modified attapulgite with magnesium and aluminum salts was conducted by batch experiments. The effects of temperatures and mass ratios of attapulgite, magnesium and aluminum salts were investigated. Linear and non-linear methods were applied for fitting the adsorption data with Langmuir, Freundlich, and Redlich-Peterson isotherms. Modified attapulgite with a mass ratio attapulgite:MgCl2·6H2O:AlCl3·2H2O = 2:1:2 had higher fluoride adsorption capacity. In addition, the fluoride adsorption using the modified attapulgite included an anion exchange process.