Defluoridation of drinking water using coalesced and un-coalesced mica

Abstract

This is a sorption study that focused on the use of mica clay mineral grouped into mica untreated, activated mica at 800 °C, mica impregnated separately with iron and aluminium for defluoridation of water. In this study, characterization of adsorbent was done by using XRF and XRD and quantification of fluoride by using fluoride ion selective electrode. Characterization of adsorbent showed the presence of SiO2, CaO, P2O5, Fe2O3 and Al2O3 in the adsorbent. XRD exhibited higher composition of illite, calcite, quartz and albite. Batch experiments were conducted by using a homogeneous mixture of water having 16 mg/L of fluoride. The removal efficiencies of mica alone, activated mica at 800 °C, mica impregnated with iron and mica impregnated with aluminium were found to be 76.02%, 90.21%, 94.40% and 96.88%, respectively. Activated mica and coalesced mica are better adsorbents than mica alone. The optimized pHs were 7.3, 4.4, 7.5, doses of 10, 9 and 8 g, contact time of 40, 35 and 30 min for activated mica, mica impregnated with iron and mica impregnated with aluminium, respectively. The adsorption process obeyed Freundlich model for mica impregnated with aluminium indicating monolayer mechanism, whereas activated mica and mica impregnated with iron agreed with both Freundlich and Langmuir models indicating both monolayer homogeneous and heterogeneous surface conditions. From the kinetic perspective, the fluoride adsorptive reaction followed the pseudo-second-order model. Therefore, activated and modified mica are alternative adsorbents for defluoridation of water.