Removal of environmental level of 239+240Pu and 241Am from groundwater by using humic coated colloidal suspension of goethite (α-FeO(OH))

Abstract

In case of natural catastrophic nuclear accident scenario like Daiichi Nuclear Power Plant (NPP) Fukushima, Japan (11 March 2011) and industrial nuclear accidents like Chernobyl, USSR (March 1986), thousands of curies of activity goes in the public domain and contaminate the drinking water system in the area around the accidental zone. In view of this there is a need to evolve methodology for decontamination of the drinking water without compromising the drinking water quality. During this work humic coated colloidal suspension of geothite(α-FeO(OH)) followed by ultrafiltration were used to decontaminate the water having 239+240Pu and 241Am in the concentration range of 10–100 Bq L−1. Polydispersive colloids of goethite were generated by controlled oxidation of FeSO4 in the presence of NaOH. Size characterization, morphology and elemental profiling of goethite suspension and their aggregation with increase in the concentration of humic acid was studied by using dynamic light scattering and scanning electron microscope hyphenated with energy dispersive spectrometry. Experimental results clearly indicate preferential association of Pu and Am with goethite suspension dominated with 30 nm colloids. The impact of humus material on selectivity of Pu and Am by goethite was studied in the concentration range of 10–100 μg mL−1 of humic acid. This selectivity is further enhanced linearly with the increase in concentration humic acid from 10 to 60 μg mL−1 and thereafter it remains constant. Goethite suspension having a coating of 60 μg mL−1 of humic acid was successfully utilized to decontaminate the water. Goethite suspension was separated from the groundwater using Ultra filtration cell with membrane having 500 NMWL (nominal molecular weight limit).