Graphene oxide encapsulated polyvinyl alcohol/sodium alginate hydrogel microspheres for Cu (II) and U (VI) removal.

In this work, a novel sodium alginate (SA)/polyvinyl alcohol (PVA)/graphene oxide (GO) hydrogel microspheres were prepared by a simple method. Sodium alginate was physically crosslinked by Ca2+; GO was encapsulated into the composite to strengthen the hydrogels; PVA played a significant role in well dispersing of GO in SA. The SA/PVA/GO (SPG) hydrogels were employed as an efficient adsorbent for removal of Cu (II) and U (VI) from aqueous solution. Batch experiments with the subject of the pH, initial metal ion concentration, competing ions and contact time were investigated. Structure characterization was successfully conducted by FTIR, SEM, EDX, BET and XPS. Furthermore, the sorption kinetics of Cu2+ and UO22+ followed pseudo-second order model and exhibited 3-stage intraparticle diffusion model. Equilibrium data were best described by Langmuir model and the obtained maximum adsorption capacities of SPG hydrogel microspheres for Cu2+ and UO22+ were 247.16 and 403.78 mg/g, respectively. The difference in adsorption capacity can be confirmed by the percentage of elements in EDX spectra and the intension of peak of elements in XPS spectra. The SPG sorbent exhibited excellent reusability after 5 adsorption-desorption cycles. All results suggested that the prepared adsorbents could be considered as effective and promising materials for removal of Cu (II) and U (VI) in wastewater.

Preparation of a novel polyacrylic acid and chitosan interpenetrating network hydrogel for removal of U(vi) from aqueous solutions.

A clean and simple method has been developed for preparation of interpenetrating polymer networks using polyacrylic acid (PAA) and chitosan (CS) for extraction of uranium from polluted water. The peak of Fourier transform infrared spectroscopy (FTIR) occurred at 928 cm-1 indicating combination of uranium and PAA/CS. The energy dispersive X-ray (EDX) and the scanning electron microscope (SEM) studies illustrated the formation of a crosslinking structure and excellent binding ability of uranium on PAA/CS. The maximum adsorption capacity was 289.6 mg g-1 calculated using the equation of the Langmuir model. The adsorption capacity reached a plateau at pH 4 and the sorption process fits the pseudo-second-order model well. The PAA/CS composite has stability of reuse, with the adsorbent capacity decreasing slowly with increasing usage frequency. The experimental results confirm that the PAA/CS hydrogel could be a novel alternative for highly efficient removal of uranium from wastewater.