Efficient fluoride removal from aqueous solution by sorption using natural adsorbent - Eugenia Jambolana : Equilibrium isotherm analysis and influence of anions

Abstract

Commercial industries which employ metallurgical extraction, cement manufacturing and fuel cells expulse heavy volumes of fluoride-containing wastewater into the natural environment posing grave threats to public health. In the current study, a locally available plant known as Jamun (Eugenia Jambolana), was used as an adsorbent for fluoride removal from aqueous solutions. Physico-chemical experiments were conducted to reveal the size and surface distribution of natural fluoride adsorption on the adsorbent surface using SEM, XRD, and FT- IR. Effects of different parameters such as solution pH, adsorbent dosage (m), co-ions contact time (t), fluoride concentration, and flow rates were investigated. Additionally, the adsorption efficiency of competing ions like Cl^-, ${\mathrm{NO}}_3^{-}$ , ${\mathrm{SO}}_4^{2-}$ , ${\mathrm{PO}}_4^{3-}$ , Ca²⁺, and Mg²⁺ and their physiological effects were studied under different solution concentrations ranging from 20 – 200 mg / L at pH 6.90±0.10 for 1 hour. Results showed that the adsorption equilibrium and kinetic data were matched with the isotherm Langmuir model (R² = 0.98) and Freundlich model (R² = 0.97). Also, we could conclude that the adsorption process of fluoride using the natural adsorbent resu bivalve shells was an endothermic reaction and resulted in a spontaneous adsorption process. Adsorption kinetic models revealed a swift adsorption rate with minimum and maximum fluoride concentrations as 100 mg / L and 500 mg / L with contact time (t) = 60 minutes at adsorbent dosage (m) = 1 g / L.