A facile synthesis of metal ion-imprinted graphene oxide/alginate hybrid biopolymeric beads for enhanced fluoride sorption

The enhanced surface properties of graphene oxide (GO) illustrate its vital role in environmental remediation. However, it is difficult to use it in column studies as it causes a pressure drop during field applications. To overwhelm its drawbacks and to improve its adsorption feature, GO was synthesized in a usable bead form by interspersing GO within an alginate (Alg) polymeric matrix and cross-linked with La(III) ions (GOAlgLa). The synthesized GOAlgLa composite beads not only display good field applications but also demonstrate an extremely enhanced defluoridation capacity (DC) compared with GO and calcium cross-linked alginate beads (AlgCa). The DC of GOAlgLa, AlgCa composite beads and GO was found to be 6617, 618 and 2438 mg F- kg(-1), respectively. To determine the effect of different influencing parameters, such as pH, contact time, competitor co-anions, temperature and initial fluoride concentration, studies were conducted in batch mode. The sorbents were analyzed using various characterization techniques such as FTIR, TEM, SEM, EDAX, and Raman analysis. The characteristics of the sorption process were investigated using Freundlich, Langmuir, and D-R isotherms. The value of the thermodynamic parameters indicates that the fluoride sorption onto GOAlgLa composite beads was endothermic and spontaneous in nature. GOAlgLa composite beads also reveal a good regenerability over repeated adsorption/desorption processes. The applicability of hybrid beads to field water sample indicate its adaptable nature at field conditions.