Poster (EARTH)

[PE1-060] Synthesis of layered double hydroxide/different carbon material composites for simultaneous adsorption of ⁷⁹SeO₄^2- and ⁹⁰Sr²⁺

○Yuta Kamura¹, Paulmanickam Koilraj¹, Tsuyoshi Hirajima¹, Keiko Sasaki¹ (1. KYUSHU UNIVERSITY)

Keywords:Layered double hydroxide, Carbon-dot, Graphene oxide, Nanocomposites, Radioactive waste

After the Fukushima Daiichi Nuclear Power Plant accident, a variety of radionuclides has been treated by Advanced Liquid Processing System including different adsorbents. This work aims to synthesize layered double hydroxide (LDH)/different carbon materials composites for simultaneous adsorption of radioactive anion and cation, where ⁷⁹SeO₄^2- and ⁹⁰Sr²⁺ have been selected as targets for removal. As carbon materials, carbon-dot and graphene oxide (GO) were synthesized to modify LDH, in which the presence of carboxylic groups was confirmed by FTIR. TEM observation revealed the sizes of C-dot and LDH particles are 3-5 nm and around 100 nm, respectively, while the size of GO has been reported 1-2 mm. Simultaneous adsorption of SeO₄^2- and Sr²⁺ was achieved in both composites using surrogates, though ion-exchange of SeO₄^2- with NO₃^- in LDH and complexation of Sr²⁺ with carboxyl group in carbon materials. Comparable adsorption capacities of SeO₄^2- was observed on both composites. However, Sr²⁺ adsorption capacities were much larger in LDH/GO than LDH/C-dot in any cases of different carbon contents. In addition, Sr²⁺ adsorption capacities in mmol/g-GO were much larger in LDH/GO composites than pure GO. Zeta potential of LDH/GO was +31.0 mV closer to LDH, while that of LDH-C-dot was -16.4 mV closer to C-dot. These observation suggests there is a clear contrast between two composites. That is, the composite of LDH/GO consists of coverage of larger sheets of GO with smaller sheets of LDH, while the composite of LDH/C-dot consists of coverage of larger sheets of LDH with nano-sized C-dot. Accordingly it is promising to customize the ratio of LDH/GO in the composite considering the different radioactive waste water compositions to treat in various stages.