Taguchi experimental design for adsorptive removal of fluoride from water using novel Ficus Glomerata Bark-developed biosorbent

Abstract

Designs of Experiments are usually applied to reduce the number of experiments, time and cost of research. The present research focuses on the application of Taguchi method for optimization of defluoridation of water using Ficus glomerata bark-developed biosorbent. The optimized conditions were found to be pH 7, initial concentration 5 mg L−1, time of contact 120 min, dose of adsorbent 10 g L−1 and temperature 30 °C. The percentage contribution by ANOVA indicates the following order: pH 60.88% > initial concentration of adsorbate 25.73% > adsorbent dose 6.78% > temperature 3.37% > contact time 3.22%. Percentage fluoride removal in the validation experiment performed at optimum conditions was found to be greater than that obtained in all the test runs of Taguchi statistical design method, hence supporting the accuracy of process parameter optimization for fluoride removal under the given set of experimental conditions. Equilibrium study points out the present sorption process is utmost fitted with Langmuir isotherm model with constants ‘a’ and ‘b’ estimated as 2.262 mg g−1 and 0.638 L mg−1. The kinetic study indicates adsorption kinetics best fits pseudo-second-order kinetics. The thermodynamic analyses suggest the spontaneous and endothermic nature (ΔH = 15.394 kJ mol−1) of fluoride adsorption. Advanced studies, viz. BET, FESEM-EDX, and FTIR, are done to know the characteristics of the biosorbent developed from Ficus glomerata adsorbent. Groundwater sample test utilizing the adsorbent revealed the percentage removal efficiency obtained is about 90% and the fluoride content in treated water is fine within drinking water specifications.