title: Enhanced fluoride adsorption using Al (III) modified calcium hydroxyapatite.
abstract: Aluminum-modified hydroxyapatite (Al-HAP) was prepared and characterized using XRD and BET analyses. Al-HAP possessed higher defluoridation capacity (DC) of 32.57 mgF(-)/g than unmodified hydroxyapatite (HAP) which showed a DC of 16.38 mgF(-)/g. The effect of Al/Ca atomic ratio in Al-HAP, solution pH and co-existing anions was further studied. The results indicated that the adsorption data could be well described by the Langmuir isotherm model and the adsorption kinetic followed the pseudo-second-order model. The pH changes during the adsorption process suggested that the OH on the surface of Al-HAP was the adsorption sites. The more adsorption sites were formed on Al modified HAP, which possessed abundant surface hydroxyl groups, resulting in higher efficiency of F(-) removal. Thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated in order to understand the nature of adsorption process. The results revealed that the adsorption reaction was a spontaneous and endothermic process.
authors: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.
authors: Yulun
authors: Y
authors: Nie
authors: Chun
authors: C
authors: Hu
authors: Chuipeng
authors: C
authors: Kong
mesh_terms: D000327:Adsorption; D000535:Aluminum / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
chemical_list: D014874:Water Pollutants, Chemical; D017886:Durapatite; D000535:Aluminum; D005459:Fluorides