Exploration of the Cs Trapping Phenomenon by Combining Graphene Oxide with α-K6P2W18O62 as Nanocomposite

Abstract

A graphene oxide-based α-K₆P₂W₁₈O₆₂ (Dawson-type polyoxometalate) nanocomposite was formed by using two types of graphene oxide (GO) samples with different C/O compositions. Herein, based on the interaction of GO, polyoxometalates (POMs), and their nanocomposites with the Cs cation, quantitative data have been provided to explicate the morphology and Cs adsorption character. The morphology of the GO-POM nanocomposites was characterized by using TEM and SEM imaging. These results show that the POM particle successfully interacted above the surface of GO. The imaging also captured many small black spots on the surface of the nanocomposite after Cs adsorption. Furthermore, ICP-AES, the PXRD pattern, IR spectra, and Raman spectra all emphasized that the Cs adsorption occurred. The adsorption occurred by an aggregation process. Furthermore, the difference in the C/O ratio in each GO sample indicated that the ratio has significantly influenced the character of the GO-POM nanocomposite for the Cs adsorption. It was shown that the oxidized zone (sp²/sp³ hybrid carbon) of each nanocomposite sample was enlarged by forming the nanocomposite compared to the corresponding original GO sample. The Cs adsorption performance was also influenced after forming a composite. The present study also exhibited the fact that the sharp and intense diffractions in the PXRD were significantly reduced after the Cs adsorption. The result highlights that the interlayer distance was changed after Cs adsorption in all nanocomposite samples. This has a good correlation with the Raman spectra in which the second-order peaks changed after Cs adsorption.

Keywords: Dawson-type polyoxometalate; cesium; graphene oxide; nanocomposite; sp2/sp3 carbon domain.

Figure 1

TEM imaging of (a) GO_c70, (b) GO_c72, and (c) GO_c39 and SEM imaging of (d) GO_c39, (e) GO_c40, and SAED pattern from the location (A1,B1,C1) marked in pictures (a–c), respectively.

Figure 2

SEM measurement: (a) [GO₇₀POM]₄₁, its EDS map (b) Tungsten element, (c) Oxygen element, (d) Carbon K-α X-ray element; TEM image: (e) [GO₇₀POM]₄₁, (f) GOc₇₀, showing the formation of (a) layer after forming the composite [GO₇₀POM]₄₁ (E1) compared with the original GO_C70 (F1) in the same-scale image (200 nm).

Figure 3

TEM image: (a) [GO₄₀POM]₄₁ after Cs adsorption, small black spots are identified (scale: 50 nm), (b) Elemental analysis of (a), (c) GO_c70 after Cs adsorption, many small Cs clusters are seen (scale: 50 nm), (d) Elemental analysis of (c).

Figure 4

PXRD patterns of GO_c70, GO_c72, and their GO-POM nanocomposite before and after Cs adsorption.

Figure 5

Raman spectra before and after Cs adsorption for (a) GO_c72 (b) [GO₇₀POM]₁₈.

Figure 6

The increment of Cs adsorption capacity (%) calculated by using the ratio before and after forming a composite in each GO sample.

Figure 7

TEM image of [GO₇₀POM]₁₈/Cs: (a) Aggregation after Cs adsorption, (b) Elemental analysis of (a).

Figure 8

IR spectra for (a) [GO₇₀POM]₁₈, (b) [GO₇₀POM]₁₈ after Cs adsorption, (c) [GO₇₀POM]₄₁, (d) [GO₇₀POM]₄₁ after Cs adsorption, (e) [GO₄₀POM]₁₈, (f) [GO₄₀POM]₁₈ after Cs adsorption, (g) [GO₄₀POM]₄₁, and (h) [GO₄₀POM]₁₈ after Cs adsorption.