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Special Articles

Characterization of Granular Montmorillonite–Polysulfone Adsorbent and Its Feasibility as a Passive Flux Meter for the Measurement of Groundwater Uranium Flux

지하수 우라늄 플럭스 측정을 위한 몬모릴로나이트–폴리설폰 입상 흡착제의 특성 규명과 플럭스미터 적용성 평가

Subeen Kim1†
,
Jimin Mun2†
,
Minjune Yang34*
김 수빈1†
,
문 지민2†
,
양 민준34*
1PhD Student, Major of Earth and Environmental Sciences, Division of Earth Environmental System Sciences, Pukyong National University
2Undergraduate Student, Major of Environmental Geosciences, Division of Earth Environmental System Sciences, Pukyong National University
3Associate Professor, Major of Environmental Geosciences, Division of Earth Environmental System Sciences, Pukyong National University
4President, Wible Co., Ltd.
1국립부경대학교 지구환경시스템과학부 지구환경과학전공 박사과정
2국립부경대학교 지구환경시스템과학부 환경지질과학전공 학부과정
3국립부경대학교 지구환경시스템과학부 환경지질과학전공 부교수
4㈜와이블 대표이사
*Corresponding Author
†These authors equally contributed to this study as first author.
31 December 2025. pp. 525-539
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Abstract

Quantifying uranium (U) mass flux in groundwater is critical for risk assessment and long-term monitoring around nuclear facilities, yet conventional passive flux meters (PFMs) are often limited by the poor structural stability and regenerability of commonly used sorbents. In this study, we developed a granular montmorillonite–polysulfone composite sorbent (MPS) and evaluated its feasibility as a PFM packing material for time-integrated measurement of groundwater U flux. Spherical MPS beads were synthesized by immobilizing powdered montmorillonite in a polysulfone matrix, and an optimal composition of 4 wt% montmorillonite was selected considering both adsorption performance and bead integrity. Batch adsorption experiments indicated that U adsorption was best described by the Langmuir isotherm, yielding a maximum monolayer capacity of 278.9 µg/g. Kinetic data were well fitted by both pseudo-first-order and pseudo-second-order models (R2 > 0.97), suggesting coupled physical and chemical interactions. Regenerability was confirmed through three consecutive adsorption–desorption cycles using 0.3 M HNO3, with both adsorption and desorption efficiencies maintained above 90%. Under continuous-flow fixed-bed column conditions (influent U = 1.2 mg/L; Darcy velocity = 0.4 m/day), a stable pre-breakthrough region was observed up to 3 pore volumes (C/C0 ≤ 0.1), from which a conservative working capacity of 0.014 mg/g was derived. Using the column-based working capacity and measured bulk density, field-scale simulations for a 10-cm-diameter well with a 20-cm-long PFM (160 g of MPS; total working capacity = 2.24 mg) predicted allowable deployment times of approximately 1–25 days for U concentrations of 0.1–0.5 mg/L and Darcy velocities of 0.05–0.2 m/day. Overall, MPS demonstrates strong potential as a robust and regenerable sorbent for PFMs, enabling reliable, time-averaged monitoring of groundwater U mass flux.

Keywords
uranium
groundwater
passive flux meter
montmorillonite
polysulfone
adsorption

지하수 내 우라늄(U) 질량 플럭스를 정량화하는 것은 원전 및 방사성폐기물 처분시설의 환경위해성을 평가하는 데 핵심 요소이지만, 기존 수동형 플럭스미터(passive flux meter, PFM)에 사용되는 입상 활성탄과 이온교환수지는 구조적 안정성과 재생성 한계로 인해 적용성이 제한된다. 본 연구에서는 점토 광물인 몬모릴로나이트를 흡착상으로, 폴리설폰을 구조 매트릭스로 이용한 입상 복합 흡착제(montmorillonite–polysulfone sorbents, MPS)를 제조하고 지하수 우라늄 플럭스 측정을 위한 PFM 내부 충진재로서의 가능성을 평가하였다. 분말 몬모릴로나이트를 폴리설폰 용액에 분산시켜 구형 비드로 성형한 후, 배치 실험과 기계적 안정성을 바탕으로 최적 조성은 몬모릴로나이트 4 wt%로 선정하였다. 등온 흡착 실험 결과, MPS의 우라늄 흡착은 Langmuir 모델에 잘 부합하였으며 최대 단일층 흡착용량은 278.9 µg/g으로 산정되었다. 동역학 실험에서 pseudo first-order 및 pseudo second-order 모델 모두 R2 > 0.97을 보여 물리·화학적 흡착이 복합적으로 작용함을 시사하였다. 0.3 M HNO3를 이용한 3회 반복 흡·탈착 실험결과, 흡착 및 탈착 효율이 모두 90% 이상 유지되어 MPS의 우수한 재사용성을 확인하였다. Darcy 유속 0.4 m/day, 초기 농도 1.2 mg/L 조건에서 수행한 고정상 컬럼 실험 결과, 약 3 PV까지 C/C0 ≤ 0.1을 유지하는 파과 이전 구간이 확인되었으며, 이 구간을 기준으로 MPS의 보수적인 작동 흡착용량은 0.014 mg/g (160 g 충진 시 총 2.24 mg)으로 산정되었다. 이를 내경 10 cm 지하수 관정 내 PFM (높이 20 cm)에 적용하여 현장 규모 모사를 수행한 결과, 우라늄 농도 0.1–0.5 mg/L, Darcy 유속 0.05–0.2 m/day 범위에서 PFM의 허용 설치 기간은 약 1–25일로 평가되었다. 종합적으로 MPS는 구조적 안정성과 반복 재생성을 동시에 확보한 우라늄 전용 흡착제로서, 지하수 우라늄 플럭스 측정을 위한 PFM 설계와 운전 지침 수립에 활용 가능한 잠재력을 갖는 것으로 판단된다.

키워드
우라늄
지하수
플럭스미터
몬모릴로나이트
폴리설폰
흡착
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Information
  • Publisher :Korean Society of Engineering Geology
  • Publisher(Ko) :대한지질공학회
  • Journal Title :The Journal of Engineering Geology
  • Journal Title(Ko) :지질공학
  • Volume : 35
  • No :4
  • Pages :525-539
  • Received Date : 2025-11-27
  • Revised Date : 2025-12-23
  • Accepted Date : 2025-12-24
  • DOI :https://doi.org/10.9720/kseg.2025.4.525
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