Figure 3. Assessment of the MagCE performance in radioactive cesium elimination from fly ash slurry under various conditions.

Ferrocyanide-type-dependent (a) degree of removal of radioactive cesium and (b) each of the SEM images (See also Fig. S16, Supplementary Information). MagCE (40 mg) composed of each type of insoluble ferrocyanide salt and acicular iron was mixed for 24 h. As ferrocyanide salts, we used iron-, cobalt-, cupper-, nickel- and zinc-ferrocyanide. (c), The appearance of four types of fly ash (See Table S1, Supplementary Information) obtained from the different refuse incineration plants and fly-ash-type-dependent removal of radioactive cesium. MagCE (40 or 400 mg) composed of nickel ferrocyanide and acicular iron was mixed. (d), Degrees of the magnetic-material-type-dependent and magnetic-separation-time-dependent removal of the radioactive cesium, which are increased by the magnetization of MagCE before its addition to the fly ash slurry. MagCE (40 mg), composed of nickel ferrocyanide, and each type of magnetic nanoparticle was mixed. As magnetic materials, we used acicular iron, spherical iron and spherical iron oxide. (e), SEM images of spherical iron oxide nanoparticle- and spherical iron nanoparticle-based MagCE (See also Fig. S17, Supplementary Information). (a), (d), Fly ash obtained from city D was used. (a), (c), (d), MagCE, which was prepared when the floating ball-height of rotameter was 45 mm, which then was mixed with fly ash slurry (fly ash: 40 g; DW: 400 mL). After the removal of MagCE using a bar type magnetic separator (See Fig. S8, Supplementary Information), the radioactivity of the slurry was measured using an Na-I scintillator. Data are expressed as the mean ± SD, All samples for the assay were prepared in triplicate.