Synthesis and characterization of multi-carboxyl-functionalized nanocellulose/nanobentonite composite for the adsorption of uranium(VI) from aqueous solutions: Kinetic and equilibrium profiles

The present study reveals a new method of preparation of an adsorbent, poly(itaconicacid)-poly(methacrylicacid)-grafted-nanocellulose/nanobentonite composite (P(IA/MAA)-g-NC/NB), using cellulose extracted from cotton for the effective removal of Uranium(VI), [U(VI)] from aqueous solutions. The adsorbent was synthesized by graft copolymerization reaction of methacrylic acid (MAA) and itaconic acid (IA) on nanocellulose/nanobentonite (NC/NB) composite using ethyleneglycol dimethacrylate (EGDMA) as cross-linker and potassium peroxydisulfate (KPS) as initiator. The adsorbent was characterized using FTIR, XRD, SEM-EDS, TG and potentiometric titrations. The carboxylic groups from two monomers increase the effective adsorptive removal of U(VI). The ability of adsorbent was studied and optimized. The optimum pH was found to be 5.5. The adsorbent dose is found to be 2.0 g/L for the removal of U(VI) from 100 mg/L. The kinetic data followed the pseudo-second-order model. The equilibrium attained at 120 min and Sips isotherm model fit well. The adsorbed U(VI) is desorbed using 0.1 N HCl. The adsorption-desorption studies conducted over 6 cycles illustrate the feasibility and repeated use of the adsorbent for the extraction of U(VI) from aqueous solutions. The practical efficacy and effectiveness of the adsorbent was tested using simulated nuclear industry wastewater and it was observed that 0.45 g/L adsorbent is sufficient for the complete removal of U(VI). (C) 2015 Elsevier B.V. All rights reserved.