Eco-friendly design of functionalized graphene oxide incorporated alginate beads for selective fluoride retention

Abstract

To defeat the troubles of fluorosis, in this present investigation aimed to fabricate sulfonated graphene oxide (SGO) encapsulated with alginate (Alg) biopolymer which gives easily separable SGO@Alg beads and is employed for efficient fluoride adsorption studies. The influence of initial fluoride ion concentration, SGO@Alg beads dosage, contact time, challenger's anions, temperature and adsorbate pH for the fluoride removal was optimized under batch method. The developed SGO@Alg beads possess highest defluoridation capacity (DC) of 4640 mgF− kg−1 within 30 min than parent materials (SGO) and graphene oxide (GO). The highest DC was attained at pH 6 under batch scale. The developed SGO@Alg beads have selective fluoride adsorption capacity while the co-anion bicarbonate acts as powerful adversary anions during adsorption. Thermal stability, functional groups interactions, surface micro-graphs and binding energy of SGO@Alg beads was studied by TGA, Raman, SEM, mapping, FTIR and XPS analysis. The equilibrium data of fluoride adsorption onto SGO@Alg beads were evaluated by adsorption kinetics, thermodynamic parameters and isotherms in detail. The isotherm of fluoride adsorption was filled by Langmuir model. The rate of the adsorption reaction was fitted by pseudo-second-order and intraparticle diffusion kinetic models. The endothermic, feasibility and spontaneous was verified by thermodynamic studies. The electrostatic interaction makes fast fluoride adsorption process on SGO@Alg beads surface. The repeatable use of SGO@Alg composite beads upto six removal cycles make it as the suitable for pilot scale water treatment studies. In addition, the aptness of SGO@Alg beads was tested with a field sample and field results exhibit that SGO@Alg beads were potentially reduced fluoride concentration below the tolerable level.