Fluoride adsorption onto granular ferric hydroxide: effects of ionic strength, pH, surface loading, and major co-existing anions.
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(-).
Tang
Yulin
Y
College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
Guan
Xiaohong
X
Wang
Jianmin
J
Gao
Naiyun
N
McPhail
Martin R
MR
Chusuei
Charles C
CC
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
D000838:Anions; D005290:Ferric Compounds; D007477:Ions; D014874:Water Pollutants, Chemical; C021024:ferric hydroxide; D005459:Fluorides