Green synthesis of iron nano-impregnated adsorbent for fast removal of fluoride from water

Abstract

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 Temkin models. The values ΔG° were - 1.89, - 0.86 and - 0.74 kJ/mol at 293, 298 and 303 K temperatures. ΔH° value was - 7.61 kJ/mol; indicating exothermic adsorption. ΔS° 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 determine