Defluoridation of water using Stevia-based adsorbent

Abstract

Fluoride contamination in groundwater negatively impacts human health, prompting global research on de-fluoridation techniques. The current study explores the de-fluoridation potential of activated carbon from Stevia plant leaves, a method based on active carbons from plant matter, which is expected to gain more attention. Surface morphological and physiochemical studies were carried out to characterize the Stevia-based activated carbon (SAC) using FT-IR, XRD, and SEM techniques. The impact of many factors, including adsorbent dose, and agitation time, pH, electrolytes, on fluoride removal was investigated. Using Freundlich (F-I), Langmuir (L-I), Temkin (T-I), and Dubinin-Radushkevich (D-R-I) isotherms, the adsorption process was examined. With SAC at pH levels of 2 to 7.4, the percentage removal of [F̅] rose from 75.4 to 93.2, and with pH increases of 7 to 11, it declined to 89.5 to 83.8%. The adsorption isotherms of F-I, L-I, T-I, and D-R-I have correlation coefficient values of 0.974, 0.989, 0.955, and 0.947, respectively. For the SAC, The D-R-I mean free energy (E) and the T-I heat of sorption (B) are 10.03 and 4.165 J mol−1, respectively. The adsorption kinetic behavior of [F̅] onto the SAC composite could be explained by the pseudo-second-order kinetic model with a good correlation coefficient when compared to the pseudo-first-order kinetic model. It was demonstrated that SAC is a useful adsorbent for de-fluoridating water. The physisorption nature of the process is supported by the B and E; both having values less than 50 kJ mol−1. The groundwater system would be effectively de-fluoridated by the method.