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

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 K_d values increased from about 10 at pH 1 to 10⁵ at pH 3 beyond which a plateau in the K_d 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.