FLUORIDE REMOVAL BY CITRUS LIMETTA PULP AND CITRUS SINENSIS PEEL USING BATCH PROCESS: KINETICS AND EQUILIBRIUM STUDIES

Abstract

In the present study removal of fluoride from synthetic water using citrus limetta (mosambi) fruit pulp powder and citrus Sinensis (Malta fruit) peel powder has been carried out through batch adsorption process. The effect of various parameters like pH, agitation time and initial fluoride concentration was studied. In case of both the materials maximum removal of fluoride is observed at pH 7. Test was also done at pH 5 and 9. In case of mosambi pulp equilibrium time has been found around 45 minutes whereas in case of Malta peel powder it was found to be around 60 minutes. At this point graph becomes almost parallel to x-axis which shows that there is no further effect of time on removal of fluoride. Initial fluoride concentration graph was found to be almost linear. It is plotted between initial concentration of fluoride and adsorption capacities at equilibrium “qe” (mg/g). To understand the phenomenon of adsorption kinetic models and equilibrium models has been applied and there constants and various parameters were also calculated. Various models applied were Langmuir, Freundlich, temkin (equilibrium models) and pseudo-first order, pseudo-second order, intra particle diffusion, Elovich model (kinetic models). In case of mosambi pulp powder Langmuir adsorption isotherm has maximum value of R^2 i.e. 0.7991 hence this model fitted well among all equilibrium models and among kinetic models the adsorption kinetics is well presented by the pseudo-first order rate equation which has maximum R^2 value i.e. 1. In case of Malta fruit peel powder temkin adsorption isotherm has maximum value of R^2 i.e. 0.9869 hence this model fitted well among all equilibrium models and among kinetic models fluoride adsorption is well explained by Elovich model which has maximum R^2 value i.e. 0.9890. There are many industries which use fluoride in production and industrial applications, such as semiconductors, fertilizers, and electrolysis of alumina; hence they contribute to fluoride pollution. Concentration of fluoride determines whether it will be harmful or beneficial in the drinking water. It has been proved that fluoride concentrations between 0.5–1.5 mg/L are beneficial especially for newborns because they prevent dental caries and tooth decay, whereas concentrations more than 1.5 mg/L cause mottling of teeth in mild cases but fluorosis (dental or skeletal) and several vi neurological disorders in severe cases. Therefore various methods and materials need to be find out which shall be economical and highly efficient in Deflouridation process. Cost is one of the important factor hence more number of low cost adsorbents should be developed.