Fluoride Ion Leaching Kinetics for Alkaline Soils of Indian Origin

Aims: The present research study describes leaching kinetics of F- by loading NaF on undisturbed vertical soil column of the soil collected from Sambhar region of Rajasthan, India.
Place of Study: Government College Kota, University of Kota, Kota, Rajasthan, India.
Methodology: Alkaline soil (pH=8.2) had been collected from Sambhar region of Rajasthan, India and was dried in open air in sunlight. Dried soil was sieved for uniform particle size. The leaching kinetics of NaF has been studied by determining the fluoride concentrations in the leachate with time. Fluoride was estimated using Fluoride Ion Selective Electrode with TISAB.
Results: Linear relationship is established between the concentrations of leachable fluoride [F-]i and initial rate of leaching (LRobs). [F-]i and LRobs are found to decrease with increase in Na+ and Ca2+ levels of extractant, while an increase has been observed with increase in temperature and OH- ions. While viewing the affect of OH- ions, the effect of its accompanying cation was also investigated which indicated that maximum [F-]i are resulted with addition of NH4OH in percolating water and minimum with addition of KOH. Total leachable F-was found to be unaffected by incubation time.
Conclusion: On the basis of the results, it is concluded that in alkaline soils, fluoride leaching will increase with increase in added NaF salts. An increase in Ca2+ levels of extractant has decreased [F-]i and LRobs. An increase in Na+ level of extractant, some of the unleachable fluoride converts into leachable form as [F-]extra. The result of the study is of great significance for developing various mathematical models for salt transport processes in alkaline soil preferable in Sambhar region of Rajasthan and elsewhere in the world.