title: [Adsorption of fluoride ions on a Ca-deficient hydroxyapatite].
abstract: A Ca-deficient hydroxyapatite (d-HAp) from the by-product of phosphate wastewater treatment has been used to remove fluoride ions. The effects of pH, coexistent calcium and magnesium ions, and chloride ions on the adsorption efficiency were investigated for the system. The results showed that d-HAp adsorbed F- efficiently within a wide pH range (4-7), and the defluoridation capacity of d-HAp remained 85%. There was no significant effect on removal of fluoride ions with addition of up to 200 times as high a concentration of Ca2+, Mg2+ and Cl-, so it suggested that d-HAp was applicable to high fluoride area. The adsorption kinetics can be described by Pseudo-second-order reaction model and the correlation coefficient R2 was 0.999 0. It was also found that the adsorption of F- on d-HAp followed the Langmuir model. The maximal static adsorption capacity was calculated as 26.11 mg x g(-1). It also suggested that ion exchange was the main mechanism during this adsorptive process.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, Key Laboratory of Yangtze River Water Environment, Ministry of Education, Tongji University, Shanghai 200092, China. liling19841217@163.com
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.forename: Zhi-Liang
authors.initials: ZL
authors.lastname: Zhu
authors.forename: Yan-Ling
authors.initials: YL
authors.lastname: Qiu
authors.forename: Hua
authors.initials: H
authors.lastname: Zhang
authors.forename: Jian-Fu
authors.initials: JF
authors.lastname: Zhao
mesh_terms: D000327:Adsorption; D002118:Calcium / Q000032:analysis / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry / Q000302:isolation & purification*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
chemical_list: D014874:Water Pollutants, Chemical; D017886:Durapatite; D005459:Fluorides; D002118:Calcium