title: Fluoride adsorption onto granular ferric hydroxide: effects of ionic strength, pH, surface loading, and major co-existing anions.
abstract: Fluoride adsorption onto granular ferric hydroxide (GFH) was investigated using batch methods, under various ionic strength, pH, surface loading, and major co-existing anion conditions. Adsorption of fluoride on GFH included an initial fast adsorption phase followed by a slow adsorption phase. Within the pH range of 2-11, fluoride adsorption equilibrium was not affected by ionic strength, but was significantly affected by pH. Maximum adsorption was achieved in the pH range of 3-6.5. Under the same pH condition, fluoride adsorption followed the Freundlich isotherm, indicating that the GFH surface was heterogeneous. X-ray photoelectron spectroscopy (XPS) and attenuated total reflection-infrared (ATR-IR) spectroscopy data showed evidence for fluoride sorption on the GFH surface via inner-sphere complexation accompanying increased hydrogen bonding and surface hydroxylation. Major anions, including phosphate, bicarbonate, sulfate, and chloride, reduced fluoride adsorption in the following order: H(2)PO(4)(-)>HCO(3)(-)>SO(4)(2-)>Cl(-).
authors.affiliation: College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
authors.forename: Yulin
authors.initials: Y
authors.lastname: Tang
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Guan
authors.forename: Jianmin
authors.initials: J
authors.lastname: Wang
authors.forename: Naiyun
authors.initials: N
authors.lastname: Gao
authors.forename: Martin R
authors.initials: MR
authors.lastname: McPhail
authors.forename: Charles C
authors.initials: CC
authors.lastname: Chusuei
mesh_terms: D000327:Adsorption; D000838:Anions; D005290:Ferric Compounds / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D013055:Spectrophotometry, Infrared / Q000379:methods; D013499:Surface Properties; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*; D014881:Water Supply
chemical_list: D000838:Anions; D005290:Ferric Compounds; D007477:Ions; D014874:Water Pollutants, Chemical; C021024:ferric hydroxide; D005459:Fluorides