Fluoride adsorption properties of three modified forms of activated alumina in drinking water

The study describes the removal of fluoride from drinking water using activated alumina (AA). AA was modified with H₂SO₄, FeCl₃ and a combination of the two to enhance fluoride adsorption. The AA adsorbents were characterized using Brunauer–Emmett–Teller surface area analysis and X-ray fluorescence. The maximum adsorption capacity of H₂SO₄- and FeCl₃-modified AA adsorbents was 4.98 mg/g, which is 3.4 times higher compared with that of normal AA. The results showed that the surface area of AA increased when modified with H₂SO₄. AA modified with FeCl₃ enhanced fluoride adsorption ability through ion-exchange between chlorine ions and fluoride ions. The fluoride adsorption properties of AA modified with both H₂SO₄ and FeCl₃ were consistent with the Langmuir model. The fluoride adsorption kinetics of the adsorbents were well described by the pseudo-second-order kinetic model.