Kinetics and Mechanism of Fluoride Removal Using Laterite

The suitability of laterite soil particle as a potential adsorbent is assessed for the removal of fluoride following batch mode of operation. The efficiency of the operation is determined by initial fluoride concentration, shaking time, shaking speed, dose and particle size of the adsorbent, pH of the solution, and temperature. The process attains equilibrium at 195 min, removing 78.2% fluoride from 10 mg dm -3 fluoride solution using fine particle size at 303 K. Thermodynamic parameters revealed that the process is spontaneous and exothermic in nature. The isotherm can be conformed to either Langmuir or Freundlich model in different temperature regions. The process follows Lagergren pseudo-first-order rate, and surface diffusion is identified as the predominating mechanism.