Elucidation of the sorptive uptake of fluoride by Ca2+-treated and untreated algal biomass of Nostoc sp (BTA394): Isotherm, kinetics, thermodynamics and safe disposal

The present study explores the sorption mechanism of fluoride from aqueous solution on to live biomass of Nostoc sp. (BTA394). Adsorptive efficiency of the algal biomass both as Ca2+-treated and without Ca2+-treatment were studied in varying fluoride concentration. The influence of several parameters like initial fluoride concentration (5-20 mg/L), time (0-14h), temperature (283.15-303.15 K) and calcium concentration (50-200 ppm) were considered. The effect of pH (1-11) was taken into account only for the untreated biomass. Instrumental analysis of the algal biomass was studied for better understanding of the adsorption mechanism. The removal process was found to follow Langmuir isotherm model (R-2 =0.9962 and 0.9945) with maximum adsorptive uptake of 4.72 mg/g and 3.49 mg/g by Ca2+-treated and Ca2+-untreated algal biomass respectively. The sorption process obeyed pseudo second order kinetic model. Thermodynamic study revealed the process to be endothermic, spontaneous and feasible in nature. The spent algal biomass was further modified which could be used as an ingredient in road construction or brick making thereby preventing the problems associated with waste disposal. Therefore, Ca2+-treated live algal biomass of Nostoc sp. (BTA394) could be a promising biosorbent for fluoride removal from aqueous solution. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.