Removal of fluoride by aluminum impregnated coconut fiber from synthetic fluoride solution and natural

Abstract

Aluminum impregnated coconut fiber ash (AICFA) was used for removal of fluoride from synthetic fluoride solution. The AICFA showed high specific area and strong affinity toward fluoride. Synthesized AICFA was characterized by pHZPC, FTIR, SEM and XRD studies. Adsorption kinetics indicated that the adsorption equilibrium was reached within 60 min and the adsorption process followed the pseudo-second-order kinetic model better. The Langmuir isotherm model could fit the experimental data well. Thermodynamic parameters such as Gibbs free energy (ΔG∘), enthalpy (ΔH∘) and entropy (ΔS∘) change of sorption were also evaluated which indicated that the adsorption process was spontaneous, feasible and exothermic in nature. Furthermore, the coexisting anions had significant effect on fluoride adsorption. Moreover, desorption study with AICFA showed that nearly 98% of fluoride could be leached out at pH 12. Further, the reusable properties of the material supported the possibility of its use commercially.

Keywords

• Coconut fiber
• Fluoride
• Adsorption
• Desorption
• Co-ions
• Thermodynamic parameters