Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT) (방사성폐기물학회지)

Korean Radioactive Waste Society (한국방사성폐기물학회)
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Study on the Species Distributions of Dissolved U(VI) and Adsorbed U(VI) on Silica Surface

용존 6가 우라늄 및 실리카 표면 흡착 6가 우라늄 화학종 분포 연구

  • Received : 2019.10.28
  • Accepted : 2020.03.06
  • Published : 2020.03.30
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Abstract

Dissolved hexavalent uranium can exist in the form of several different chemical species. Furthermore, species distributions depend on the pH value of the aqueous solution. Representatively, UO22+, UO2OH+, (UO2)2(OH)22+, and (UO2)3(OH)5+ species coexist in solutions at acidic and circumneutral pH values. When amorphous silica particles are suspended in an aqueous solution, the dissolved chemical species are easily adsorbed onto silica surfaces. In this study, it was examined whether the species distribution of the adsorbed U(VI) on a silica surface followed that of the dissolved U(VI) in an aqueous solution. Time-resolved luminescence spectra of three different dissolved species (UO22+, UO2OH+, and (UO2)3(OH)5+) and two different adsorbed species (≡SiO2UO2, ≡SiO2(UO2)OH-, or ≡SiO2(UO2)3(OH)5-) were measured in the pH range 3.5-7.5. The spectral shapes of these chemical species were compared by changing the pH value; consequently, it was confirmed that the species distribution of the adsorbed U(VI) species was different from that of the dissolved U(VI) species.

용존 6가 우라늄은 다양한 화학종으로 존재하며, 화학종의 분포는 수용액의 pH에 의존한다. 산성 및 중성 근처의 pH 환경에서는 대표적으로 UO22+, UO2OH+, (UO2)2(OH)22+, (UO2)3(OH)5+ 화학종이 공존한다. 수용액 속에 비결정성 실리카가 콜로이드 성질의 부유입자 상태로 존재할 때 용존 화학종은 실리카 표면에 쉽게 흡착된다. 이 연구에서는 표면 흡착 화학종의 분포가 용존 화학종의 분포를 따르는지 조사하였다. 시료의 pH 값이 3.5-7.5인 조건에서 3종의 용존 화학종(UO22+, UO2OH+, (UO2)3(OH)5+)과 2종의 표면 흡착 화학종(≡SiO2UO2, ≡SiO2(UO2)OH- 또는 ≡SiO2(UO2)3(OH)5-)의 시간 분해 발광(luminescence) 스펙트럼을 측정하였다. pH 변화에 따른 각 화학종의 스펙트럼 변화 양상을 비교한 결과로 표면 흡착 U(VI) 화학종의 분포는 용존 U(VI) 화학종의 분포와 다르다는 것을 확인하였다.

Keywords

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