مهناز احمدیان

Shortage of fluoride in water sources leads to numerous health problems. Also excess fluoride concentration is a more serious threat for health of community. Thus investigating of various physical, chemical, and biological processes for excess fluoride reduction from water supplies is considerable. This study aimed to reduce fluoride ion concentration from aqueous solutions by adsorption process by iron-coated pumice.
Firstly, the pumice pieces were grinded and sized. After several preparation stages pumice particles were covered by 0.5 N iron nitrates (III) solution. Then the effect of parameters including pH (2-10), reaction time (5-120 min), initial fluoride concentration (3– 20 mg/L), and the adsorbent dose (0.1-1.5 g/L) on removal efficiency of fluoride were investigated in a batch system. Finally adsorption isotherms and kinetics models were determined.
The results showed that the removal of fluoride increased by increasing of reaction time and adsorbent dose, and reduced by increasing of initial fluoride concentration. The Iron coated pumice exhibited the best performance for fluoride removal (84.3%) at fluoride concentration 3 mg/L, adsorbent dose 0.5 g/L, pH= 6, and contact time 30 min. The adsorption equilibrium data fitted well with the Langmuir model (R2= 0.9989), and kinetic adsorption study showed that pseudo-second order kinetic is more favorable.
According to results, the iron-coated pumice is an efficient, low cost and available adsorbent that can be considered for eliminating of fluoride ions from aqueous solutions.