Defluoridation of water by activated carbon prepared from banana (Musa paradisiaca) peel and coffee (Coffea arabica) husk

The defluoridation of ground water is regarded as one of the key areas of attention among the universal water community. The present investigation deals with fluoride removal from aqueous solution by thermally activated biosorbents prepared from banana (Musa paradisiaca) peel and coffee (Coffea arabica) husk. Fluoride ion selective electrode was used for the determination and monitoring of fluoride ion concentration. Batch experiments were conducted to establish the optimal conditions like pH, dose of the adsorbent, and contact time. The optimum pH was found to be 2 for both the adsorbents, and the optimum dose was found to be 24 g/ 250 mL at 13 h contact time for banana peel and 18 g/250 mL at 3 h contact time for coffee husk. The concentrations determined in real water samples of flour factory, poultry, and Lake Hawassa sites were 12.54, 11.02, and 6.72 mg/L, respectively. The prepared biosorbents were applied on these water samples under optimized conditions and found to be effective with removal efficiency ranging from 80 to 84 %. In terms of time and adsorbent dose required, coffee husk was observed to be much better than banana peel. The adsorption process obeyed Langmuir adsorption model. From the kinetic perspective, the fluoride adsorption followed the pseudo second-order reaction kinetics.