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

Abstract

This study evaluated the potential of montmorillonite as a reactive medium for Cr(VI) remediation through dithionitemediatedreduction of structural Fe(III) to Fe(II). Batch experiments revealed that dithionite treatment generated up to 19.1 mg/gFe(II), representing 83% of total structural iron (23 mg/g). The reduction behavior was governed by redox potentialequilibrium 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 thatreduced Cr(III) was immobilized as Cr(OH)3 on clay surfaces, with no aqueous total chromium detected. In the columnexperiments, 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 breakthroughup 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. Dithionitereinjection successfully regenerated the reductive zone and restored the Cr(VI) removal capacity, thereby extending theoperational lifetime of the reactive medium.