Green Synthesis of Iron Nano-Impregnated Adsorbent for Fast Removal of Fluoride from Water

Iron nano-impregnated adsorbent was synthesized, characterized and applied for fluoride subtraction from the water. Maximum fluoride removal (90%) was at 4.0 mg/L concentration, 25.0 min. contact time, 7.0 pH, 2.5 g/L dose and 293 K temperature. Iron nanocomposite adsorbent was selective for fluoride removal. The experimental data obeyed Langmuir, Freundlich and Temldn models. The values Delta G degrees were -1.89, -0.86 and -0.74 kJ/mol at 293, 298 and 303 K temperatures. Delta H degrees value was -7.61 kJ/mol; indicating exothermic adsorption. Delta S degrees value was -2.30 x 10(-2) kJ/mol K; a signal of entropy decrease during adsorption. The adsorption process was in the order of 293 > 298 > 303 K. Kinetic modeling confirmed pseudo-first-order and liquid film diffusion mechanisms. The mechanism of adsorption is also determined. (C) 2015 Elsevier B.V. All rights reserved.