Superparamagnetic graphene oxide-magnetite nanoparticle composites for uptake of actinide ions from mildly acidic feeds.

Super paramagnetic graphene oxide (GO) - Fe3O4 nanoparticle composites were prepared and characterized by conventional techniques such as XRD, SEM, EDX, FT-IR, Raman, XPS, DLS and zeta potential, etc. TEM studies have confirmed nanoparticle nature of the composites. The GO-magnetic nanoparticle composites can be dispersed in mildly acidic aqueous solutions and get concentrated in a small volume under application of an external magnetic field. The composites were evaluated for the uptake of actinide ions such as Am3+, UO22+, Th4+ and Pu4+ from mildly acidic aqueous solutions. Am3+ sorption sharply increased with pH as the Kd values increased from about 10 at pH 1 to 105 at pH 3 beyond which a plateau in the Kd values was seen. Eu3+ displayed nearly comparable uptake behaviour to that of Am3+ while the uptake of other metal ions followed the trend: Pu(IV)>Th(IV)>>UO22+. The adsorption behaviour of Am3+ onto the graphene oxide - Fe3O4 nanoparticle composites fitted very well to the Langmuir as well as Temkin isotherm models. The desorption rate (using 1M HNO3) was fast and reusability study results were highly encouraging. The very high uptake values suggest possible application of the magnetic nanoparticles in radioactive waste remediation in natural ground water.