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Devastating effect of fluoride in drinking water on human health is a great concern and defluoridation is essential to make groundwater suitable for drinking. The aim of this study is to evaluate the dissolved fluoride removal efficiency of a novel and low-cost carbon/carbon nanotube (CNT) composite under batch conditions. CNTs are coated on the coconut-shell charcoal surface at 450 C by using plasma-enhanced chemical vapor deposition. Thereafter, processed charcoal samples are ball milled and used for the fluoride removal from aqueous medium. The amount of fluoride removal is found to be %65% of the initial concentration of 4.4 mg L À1 in 3 h contact time at the adsorbent dose of 10 g L À1 . The linear forms of three isotherm models (Langmuir, Freundlich, and Temkin) and two kinetic models (pseudofirst order and pseudo-second order) are applied to the adsorption data to determine the best fit for equilibrium expression. Isotherm data fit the Langmuir model while the adsorption kinetics is represented by the pseudosecond-order kinetic model. The fluoride adsorption process onto prepared carbon/CNT composite occurred spontaneously (ΔG ¼ À1.656 kJ mol À1 ) in an endothermic nature (ΔH ¼ 11.07 kJ mol À1 ) with increased randomness (ΔS ¼ 41.69 J mol À1 K À1 ). To validate the performance further, the asprepared adsorbent is successfully used to treat groundwater samples with excess fluoride concentration collected from Nalgonda district, Telangana, India.

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In this work, we first electrospun cellulose acetate into nanofibers followed by deacetylation using NaOH in ethanol solution. Deacetylation of cellulose acetate fiber mat regenerated cellulose to yield cellulose nanofibers as confirmed by Raman spectroscopy. Further, as-obtained cellulose nanofibers were pyrolyzed at 900 °C in the inert atmosphere to yield cellulose acetate derived electrospun carbon nanofibers. Morphological changes during deacetylation and carbonization were examined by SEM imaging. Almost 55% shrinkage was observed during pyrolysis to finally obtain carbon nanofibers with average diameter 474.1 nm. This cellulose acetate derived free standing carbon nanofiber mat was then assembled as an anode in half-cell configuration without using any binder and then tested for its electrochemical performance using cyclic voltammetry and charge/discharge experiments. At 37.2 mA/g current density (0.1 C rate), specific capacity value after 100 cycles was stabilized at 290 mAh/g.