Biosorption of fluoride from aqueous solution by white—rot fungus Pleurotus eryngii ATCC 90888

• Potential of Pleurotus eryngii is described first time in literature for fluoride removal from water.
• Maximum fluoride removal capacity of fluoride on P. eryngii was 66.6 mg g−1.
• Fluoride removal to levels below the 1.5 ppm drinking water limit was achieved.
• P. eryngii is an environmentally safe biosorbent with no disposal problem.

In present study the biosorption characteristics of fluoride anions from aqueous solution using white rot fungus (Pleurotus eryngii) were investigated as a function of pH, initial fluoride concentration, biosorbent dose, temperature, and contact time. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were applied to describe the biosorption isotherm of fluoride ions by P. eryngii biomass. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The monolayer biosorption capacity of P. eryngii biomass for fluoride ions was found to be 66.6 mg g−1. Thermodynamic parameters such as ΔH°, ΔS° and ΔG° indicate that the removal of fluoride ions by fungal biomass was endothermic and spontaneous in nature. Experimental data were also analyzed in terms of kinetic characteristics and it was found that biosorption process of fluoride ion followed well pseudo-second order model, where intra-particle diffusion was not the only rate-controlling step. The surface and sorption characteristics were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and Fourier transform infrared (FTIR) spectrometry. In order to check the practical utility of the studied biosorbent, batch studies were carried out with fluoride contaminated water samples collected from a fluoride-endemic area. Eventually, this fungal biomass recommended to be used as a suitable, environment friendly and low cost biosorbent for removal of fluoride ion concentration to standard permissible limit.

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