Deflouridation of water using physico-chemically treated sand as a low-cost adsorbent: An equilibrium study

In this study, heat and chemically treated sand was applied as an adsorbent for the removal of fluoride ions from aqueous solutions. The influence of different parameters such as calcination time, dosage, initial fluoride concentration and pH were evaluated. Results indicated that activated sand can be used for defluoridation of water. This can be achieved by coating sand with 10% Fe2O3, a calcination time of 3 h and pH around 6. The adsorption also increased with initial fluoride concentration and adsorbent dose.  This study also showed that up to 90% of fluoride was adsorbed with 12 g of adsorbent in 50 ml of 10 mg/L fluoride solution. The sorption data were best described by the Freundlich isotherm. The maximum adsorption capacity was found to be 10.3 mg/g. According to these findings, physico-chemically modified sand has potential application as an adsorbent for fluoride ions removal.   Key words: Sand, adsorption, fluorine, defluoridation, Freundlich isotherm, Langmuir isotherm