A potential novel approach for in situ chemical oxidation based on the combination of persulfate and dithionite

Highlights: • PS/dithionite system was an effective system for TCE degradation. • The optimal molar ratio of PS/dithionite/TCE was 5/5/1. • Sulfate radical was responsible for TCE degradation in PS/dithionite system. • Two pathways of SO₄• ⁻ generation were proposed in PS/dithionite system. • Oxygen had a significant effect on TCE degradation by PS/dithionite system. -- Abstract: Although persulfate (PS) activation has been commonly applied to remove organic contaminants on the subsurface, it is valuable to further explore PS activation methods. In this study, a novel combined process based on PS coupled with dithionite was investigated using trichloroethene (TCE) as a typical organic contaminant. PS/dithionite was demonstrated to be an effective system for TCE degradation depending on the operating parameters such as the initial PS and dithionite dosages. The optimal molar ratio of PS/dithionite/TCE was 5/5/1. Sulfate radicals (SO₄• ⁻) were the dominant reactive species responsible for TCE degradation in the PS/dithionite system. Two pathways for SO₄• ⁻ generation were proposed in the PS/dithionite system. The generation of SO₄• ⁻ increased in the presence of oxygen but was still effective in an anaerobic environment. This study is the first to report a novel combined process based on PS coupled with dithionite, which is expected to be an efficient and environmentally friendly approach for in situ chemical oxidation (ISCO) remediation of contaminated soil and groundwater, whether in aerobic or anaerobic environments.