Batch sorption studies on the removal of fluoride ions from water using eco-friendly conducting polymer/bio-polymer composites

Batch sorption system using eco-friendly conducting polymer/bio-polymer composites viz. polyaniline/chitosan (PANi/Ch) and polypyrrole/chitosan (PPy/Ch) as adsorbents were investigated to ensnare fluoride ions from aqueous solutions. The system variables studied include initial concentration of the sorbate, agitation time, adsorbent dose, pH, co-ions and temperature. The experimental data fitted well to the Langmuir and Freundlich isotherms. The amounts of fluoride ions adsorbed per unit mass of the adsorbents were found to be 5.9 mg/g for PANi/Ch and 6.7 for PPy/Ch, at 50 °C from 10 mg/L fluoride solution. Thermodynamic parameters indicated that the removal of fluoride ions is an endothermic process. FT-IR, X-ray, SEM and EDAX patterns of the polymer composites before and after exposure to fluoride ions suggested that the defluoridation occurs via dopant-exchange mechanism on the N-atoms present in these constituent polymers.

Research Highlights
► Removal of fluoride occurs through ion-exchange mechanism.
► Polypyrrole composite exhibited higher fluoride removal capacity.
► Removal of fluoride ions is an endothermic process.
► Adsorbents exhibit commendable fluoride removal capacity in a wide range of pH.