Defluoridation using adsorption: a review on batch analysis parameters, kinetics, isotherms, activation energy and thermodynamics

Abstract Fluoride is one of the common contaminants present in groundwater and in waterbodies in general. It can create serious health hazards if ingested more (>1.5 mg/L). Scientists understands that removing fluoride from ground water is a difficult task. Several techniques like coagulation, membrane filtration, etc. are available for treatment but because of the high processing costs, such technologies are not always suitable for developing countries. As a result, environmentally friendly and low-cost technology like adsorption is one such method that can be successfully employed for fluoride removal. Fluoride was removed using a variety of low-cost adsorbents such as tamarind seed, tamarind gel, and duck weed etc. by defluoridation using adsorption and can be considered as one of the efficient and practical technique. This review article reports for the successful and efficient use adsorption and various adsorbents for the defluoridation of contaminated water. Observations have been reported for batch studies done by several researchers for effect of various parameter like initial concentration, temperature, contact time, pH, stirring rate on defluoridation from aqueous solution which can be supported from the fact that most of the researches done follows Pseudo second order kinetic model which suggests that the rate of adsorption is substantial and adsorption is an effective tool for the removal of fluoride from contaminated water. Isotherm studies reveal that most of the adsorption follows either Langmuir or Freundlich models. Overall, the research analyses suggests that adsorption technique can be regarded as one of the important techniques for defluoridation of contaminated waters.