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Investigation of Sorption Reaction of Re(VII) onto HDPy- and HDTMA-modified Bentonite

HDPy 및 HDTMA로 개질된 벤토나이트에 대한 Re(VII)의 흡착반응 분석

  • Jun-Myung Choi (Korea Hydro & Nuclear Power Co., Ltd.) ;
  • Junhyuk Ha (School of Mechanical Engineering, Pusan National University) ;
  • Ranyeong Choi (School of Mechanical Engineering, Pusan National University) ;
  • Jun-Yeop Lee (School of Mechanical Engineering, Pusan National University)
  • 최준명 (한국수력원자력(주)) ;
  • 하준혁 (부산대학교 기계공학부) ;
  • 최란영 (부산대학교 기계공학부) ;
  • 이준엽 (부산대학교 기계공학부)
  • Received : 2024.07.05
  • Accepted : 2024.09.11
  • Published : 2024.09.30

Abstract

Technetium-99 (99Tc) is recognized as a critical concern in the disposal of spent nuclear fuel due to its long half-life and remarkable stability, existing predominantly as TcO4- in the natural environment. The anionic form of technetium is highly soluble and mobile, posing significant environmental risks from the viewpoint of nuclear waste management. Thus, developing efficient and cost-effective sorbents for aqueous Tc(VII) is essential for mitigating relevant contamination. In the present work, the adsorption characteristics of Re(VII), a chemical analog of Tc(VII), were investigated using the clay mineral bentonite, modified with two different organic cations: hexadecylpyridinium (HDPy) and hexadecyltrimethylammonium (HDTMA). Sorption experiments were conducted at a liquid-to-solid ratio of 1 g/L with Re(VII) solutions prepared at concentrations from 10-4 mol/L to 10-6 mol/L. The sorption ratio and distribution coefficients were determined with samples collected at reaction times of 10, 50, 100, and 500 minutes after 0.45 ㎛ syringe filtration. In parallel, the modified bentonite samples were further analyzed using the X-ray diffraction (XRD) method to understand the adsorption mechanism of Re(VII) onto the target minerals. According to the quantification analysis results, a rapid equilibrium reaction of aqueous Re(VII) for all modified bentonite samples was identified. Moreover, near-complete adsorption of Re(VII) was observed when the bentonite was modified at 200-400% of its cation exchange capacity (CEC) for both organic cations. For cases of lower modification, the HDTMA-modified bentonite showed relatively higher adsorption efficiency compared with the one modified with HDPy. This result was inferred to be due to the difference in inter-layer spacing based on the characteristics of the organic cations. It is expected that the results obtained through this study will serve as a preliminary case for the synthesis of adsorbents for the retardation of highly mobile anionic radionuclides, such as I and Tc, in the natural environment.

Keywords

Acknowledgement

이 과제는 부산대학교 기본연구지원사업(2년)에 의하여 연구되었음.

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