Statistical optimization and characterization of fluoride biosorption using dead microbial biomass

Abstract

Excessive fluoride consumption (> 2.0 mg/L) results in fluorosis, teeth staining, or bone weakening. It is critical to concentrate on the defluoridation of water. Adsorption has been a conventional method of fluoride removal in aqueous solution. Biosorbents are cost-effective, easily obtainable, and ecologically sustainable sources of adsorbents. In this study, aqueous fluoride solution is treated with dead bacterial biomass. Effects of process conditions like initial fluoride concentration, biomass dosage, pH, temperature, and contact time have been studied. Central Composite Design (CCD) with 30 experiments is performed. The centre point experimental conditions have been repeated 6 times. The optimum fluoride biosorption of 76.89% is observed after 8 h of biosorption with 3.25 mg L^-1 initial fluoride concentration, 775 mg L^-1 of biomass dosage, at temperature 55 ℃ and pH 4.5. R² value of the experimental design is found to be 0.92. Biosorption kinetic studies revealed that fluoride biosorption followed a pseudo-second-order kinetics and adsorption isotherm is best described by Freundlich isotherm. The biosorption efficiency of immobilised biosorbent is also studied using column approach. Biosorbent is characterised using SEM, FTIR and EDX techniques. The desorption and recyclability studies suggest that dead bacterial biomass could serve as a potential biosorbent for fluoride biosorption.