Defluoridation of Aqueous Solution by Graphene and Graphene Oxide Nanoparticles: Thermodynamic and Isotherm Studies

Fluoride, a non-essential element, can enter water resources through several natural processes and human activities. The benefits and risks of fluoride depend on the concentration of this anion on drinking waters. In the present study, the performances of graphene and graphene oxide nanoparticles were investigated for the removal of fluoride from aqueous solution. In the present research, effects of pH, contact time, fluoride initial concentration, adsorbents dosage, as well as temperature in performance of graphene and graphene oxide nanoparticles in removal of fluoride from aqueous solution were examined. Also, isotherms and thermodynamics of the adsorption process were evaluated. For both adsorbents, the maximum adsorption capacities observed during the first 15 minutes at pH=3 and an initial fluoride concentration of 10 mg/L. The results also showed that adsorption of fluoride by graphene and graphene oxide fitted well with Freundlich and Langmuir isotherms, respectively. Furthermore, temperature increase resulted in the adsorption capacity decrease, indicating an exothermic adsorption reaction. According to the results of this research, graphene nanoparticles have higher adsorption capacity of fluoride than graphene oxide nanoparticles.