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2025 Vol.30, Issue 6 Preview Page
Immobilization of Hexavalent Chromium Through Reductive Zones Generated by Fe-bearing Clay Mineral Acting as an Electron Mediator

철 함유 점토광물의 전자 매개를 이용한 환원구역 생성과 이를 통한 6가 크롬의 고정화

Changyu Moon1
,
Sang Hyun Kim2
,
Jaeshik Chung2
,
Kyoungphile Nam1*
문찬규 1
,
김상현 2
,
정재식 2
,
남경필 1*
1Department of Civil and Environmental Engineering, Seoul National University, Seoul 08826, South Korea
2Water Cycle Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, South Korea
1서울대학교 건설환경공학부, 한국과학기술연구원 물자원순환연구단
2서울대학교 건설환경공학부, 한국과학기술연구원 물자원순환연구단
*Corresponding Author
31 December 2025. pp. 63-72
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Abstract

This study evaluated the potential of montmorillonite as a reactive medium for Cr(VI) remediation through dithionite-mediated reduction of structural Fe(III) to Fe(II). Batch experiments revealed that dithionite treatment generated up to 19.1 mg/g Fe(II), representing 83% of total structural iron (23 mg/g). The reduction behavior was governed by redox potential equilibrium rather than reductant concentration. The generated Fe(II) effectively reduced Cr(VI) following a 3:1 stoichiometry, with all Fe(II) quantitatively consumed for Cr(VI) removal. Solid-phase analysis using SEM-EDS and XPS confirmed that reduced Cr(III) was immobilized as Cr(OH)3 on clay surfaces, with no aqueous total chromium detected. In the column experiments, a 2 PV pulse injection of 50 mM dithionite lowered the ORP to -200 mV and generated structural Fe(II) within the medium. Following dithionite flushing, continuous injection of Cr(VI) solution exhibited delayed breakthrough up to 10 PV, indicating that the structural Fe(II) within the solid matrix served as an electron donor for Cr(VI) reduction. Sectional analysis and EPMA mapping confirmed immobilized Cr associated with montmorillonite particles. Dithionite reinjection successfully regenerated the reductive zone and restored the Cr(VI) removal capacity, thereby extending the operational lifetime of the reactive medium.

Keywords
Hexavalent chromium
Fe-bearing montmorillonite
Structural Fe(II)
In situ reductive zone
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Information
  • Publisher :The Korean Society of Soil and Groundwater Environment
  • Publisher(Ko) :한국지하수토양환경학회
  • Journal Title :Journal of Soil and Groundwater Environment
  • Journal Title(Ko) :지하수토양환경
  • Volume : 30
  • No :6
  • Pages :63-72
  • Received Date : 2025-10-10
  • Revised Date : 2025-10-21
  • Accepted Date : 2025-11-09
  • DOI :https://doi.org/10.7857/JSGE.2025.30.6.063
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