U(VI) capture from water-based systems by decorated nanohybrid of Zn-BTC MOF with GQDs-rGO and alginate hydrogel

Abstract

In this work, zinc-based MOF utilizing trimesic acid (Zn-BTC) was combined with carbon-based materials, viz. graphene quantum dots (GQDs) and reduced graphene oxide (rGO) and all were crosslinked with alginate hydrogel to finally generate Zn-BTC@GQDs-rGO@Alg hydrogel as a novel nanohybrid composite with various incorporated oxygen functionalities. The well-formed beads of Zn-BTC@GQDs-rGO@Alg hydrogel composite were employed to favor adsorptive capture and uptake of U(VI) from water due to the strong binding affinity of U(VI) ions to the loaded oxygen functional groups in the assembled composite. Multiple active functionalities, crystalline structure and average particle size (19.43 nm) were characterized. The EDX analysis referred to C: 47.89%, O: 44.77%, Zn: 0.43%, Ca: 2.82%, Cl: 1.74%, and Na: 2.23%. U(VI) adsorptive uptake was based on endothermic and spontaneous. Linear-nonlinear kinetic expressions confirmed high fitted to pseudo-second order kinetics with R2 0.99 and 0.94 for linear and nonlinear, respectively, while, the good agreement between the computed qe = 36.76 mg/g and qexp = 39.01 mg/g referred to the best fitting process by this model. The adsorptive uptake isotherms of U(VI) denoted mostly to good fitting with Langmuir adsorption isotherm in both linear and nonlinear representations. Zn-BTC@GQDs-rGO@Alg hydrogel as a novel nanohybrid composite was successfully implemented in removal of U(VI) from seawater, tap water and wastewater providing uptake percentages 93.52%, 90.51% and 92.68%, respectively. The evaluated composite was recycled 5 times and exhibited excellent effectiveness and high stability in U(VI) uptake with higher uptake capability when compared to other adsorbents.