Potential use of CeO2, TiO2 and Fe3O4 nanoparticles for the removal of cadmium from water

Inorganic nanoparticles (NPs) of cerium oxide (CeO2), iron oxide (Fe3O4) and titanium oxide (TiO2) were studied for the removal of dissolved cadmium from water at concentrations ranging from 25 to 350 mg/L. Adsorption was the predominant mechanism for sequestration, and particularly efficient cadmium removal was demonstrated for Fe3O4 NPs. Experimental data were fitted to three different adsorption isotherms: Langmuir, Freundlich and Temkin. The best fit was obtained for the Freundlich isotherm (R-2>0.96 for all NPs). Adsorption was shown to follow pseudo second-order kinetics (R-2 >= 0.91 for all NPs). All three NPs showed some removal of cadmium in aqueous solution, but after 72 h of process, Fe3O4 NPs showed a higher capacity of cadmium adsorption (101.1 mg Cd/g NP) than CeO2 NPs (49.1 mg Cd/g NP) or TiO2 NPs (12.2 mg Cd/g NP). These results demonstrate the potential use of this NPs to remove dissolved cadmium at high concentrations.