Removal of Fluoride Ion from Water Using locally Produced Adsorbent

Abstract

This Research investigated the adsorption capacity of locally prepared adsorbents from Egg shells for the removal of fluoride ion in well water. It evaluated the performance of these adsorbents calcinated at 3000C and modified with 1.0M HNO3 (trioxonitrate (v)) acid. Batch adsorber was used to allow for interaction between adsorbent (grounded Egg shells) with water containing fluoride ion. The batch experiment was performed with particle size of 2.12 contact time (60, 120, 180, 240, 300min), mass dosage (5g, 10g, 15g, 20g) and temperature (250C, 300C, 400C, 500C). The modified adsorbent was characterized to determine the physiochemical properties of grounded Egg shells (GE). Also the chemical composition of the modified adsorbent was analyzed to determine the percentage of calcium element required for the uptake of the fluoride ions in water for calcium as 39.68% for grounded Egg shells (GE). Percentage adsorption increased with increase in contact time, mass dosage and temperature for the adsorbent. The adsorption capacity was also determined which also increased with increase in contact time, temperature but decreased with increase in mass dosage at constant time of 60minutes. The pseudo first-order, pseudo second order and intraparticle diffusion kinetic models were fitted into the experimental results. The results obtained indicated that the pseudo first order and intraparticle diffusion models for the grounded Egg shells (GE) reasonably described the adsorption process very well whereas the pseudo second order model was not suitable for a calcinations temperature of 3000C and particle size of 2.12m. The adsorption isotherms were obtained from equilibrium experiment Performed at temperature of 25, 35, 45 and 550C. The result showed that Langmuir and Freundlich isotherm fitted perfectly the experimental data. However, the negative values of Gibb’s free energy indicated that adsorption was favourable and the positive enthalpy change H0 revealed that adsorption process was endothermic while the positive value of the entropy change signified increased randomness with adsorption.