☆ 4.7 Article

Establishment of sulfate radical advanced oxidation process based on Fe2+/O2/dithionite for organic contaminants degradation

CHEMICAL ENGINEERING JOURNAL (2021)

Journal

CHEMICAL ENGINEERING JOURNAL

Volume 410, Issue -, Pages -

Publisher

ELSEVIER SCIENCE SA

DOI: 10.1016/j.cej.2020.128204

Keywords

Ferrous iron; Dithionite; Dissolved oxygen; Sulfate radical; Generation approach; Degradation pathway

Funding

Shenzhen Scientific Research Foundation for High-level Talent [KQJSCX20180328165658476]
Shenzhen Scientific Fundamental Research Foundation [JCYJ20180306171843211, JCYJ20200109113006046, JCYJ20180306172051662, KCXFZ202002011006362]
Major Science and Technology Program for Water Pollution Control and Treatment in China [2017ZX07401001006]

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Abstract

The study introduced DTN as a novel sulfate radical generation source and successfully degraded ATZ in the Fe2+/O-2/DTN system, investigating the degradation pathways of ATZ and generation mechanism of dominant reactive species.

The sulfate radical advanced oxidation process is considered as one of the most effective technologies for refractory organic pollutant removal. However, the current sulfate radical generation source is very limited, and so far only peroxydisulfate, peroxymonosulfate and sulfite were reported as the generation sources. In this study, dithionite (DTN) was introduced as sulfate radical generation source for the first time. It was combined with Fe2+ and O-2 to form a simple and effective oxidation system: Fe2+/O-2/DTN. The established system was used to degrade atrazine (ATZ). The degradation pathways of ATZ and generation mechanism of dominant reactive species in Fe2+/O-2/DTN system were investigated. The results showed that ATZ and the total organic carbon (TOC) have been significantly reduced in 20 min with the initial solution pH varying from 5.0 to 7.0 in Fe2+/O-2/ DTN system. Moreover, the possible degradation pathway of ATZ has been proposed involving dealkylation, dechlorination, carbonylation and hydroxylation. Primary radical identification through quenching experiments, ESR spectra and density functional theory (DFT) revealed the existence of sulfate radical (SO4 center dot-) and hydroxyl radical (center dot OH) in the system. It is suspected that FeSO3+ is the possible precursor of SO3 center dot and SO4 center dot-. Therefore, the generation of FeSO3+ and the possible formation pathways of SO3 center dot and SO4 center dot have been predicted based on the results of alternating reaction atmosphere test. The study indicates that Fe2+/O-2/DTN system could generate SO4 center dot and has great potential for the remediation of organic micro-pollution water bodies and contaminated soil.

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Anoxic photochemical weathering of pyrite on Archean continents

Jihua Hao, Winnie Liu, Jennifer L. Goff, Jeffrey A. Steadman, Ross R. Large, Paul G. Falkowski, Nathan Yee

Summary: The article discusses a photochemical mechanism of pyrite weathering that could have provided substantial amounts of sulfate to the oceans during the late Archean period. Experiments showed that pyrite grains exposed to UV light in anoxic ferrous iron solutions produced high concentrations of sulfate. Additional experiments with shale demonstrated that photochemically derived ferric iron could oxidize and dissolve sedimentary pyrite during chemical weathering. The results suggest that before the rise of atmospheric oxygen, oxidative pyrite weathering on Archean continents was controlled by sunlight exposure.

SCIENCE ADVANCES (2022)