Reductive removal of nitrate by carbon dioxide radical with high product selectivity to form N2 in a UV/H2O2/HCOOH system

Chen, Jialin; Liu, Jianyong; Zhou, Jingshu; Chen, Dong

doi:10.1016/j.jwpe.2019.101097

Cited by 13 publications

(1 citation statement)

References 57 publications

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“…Formic acid (HCOOH) is photosensitive and can be photolyzed into formyl radicals (HCO • ), hydroxyl radicals ( • OH), carboxyl radicals ( • COOH), and hydrogen radicals (H • ) under ultraviolet (UV) irradiation, leading to the subsequent formation of CO, CO 2 , and H 2 gas by a series of reactions. − The formed HCO • [E 0 ((H + , CO)/HCO • ) = −1.54 V], • COOH [E 0 (H 2 CO 3 / • COOH) = −1.84 ± 0.22 V], , and H • [E 0 (H + /H • ) = −2.42 V] radicals are strongly reductive, which can reductively remove or degrade a variety of inorganic and organic pollutants. − It seems that the HCO • , • COOH, and H • radicals generated from the UV/HCOOH process can thermodynamically reduce As(V) [E 0 (As(V)/As(III)) = 0.55 V and 0.56 V] , and As(III) [E 0 (As(III)/As(0)) = 0.24 V and 0.248 V]. , Therefore, we deduce that As(V) and As(III) can be reductively removed in the form of As(0) by the homogeneous UV/HCOOH process, and then, As(0) can be easily separated and recovered from wastewater.…”

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confidence: 99%

Reductive Removal and Recovery of As(V) and As(III) from Strongly Acidic Wastewater by a UV/Formic Acid Process

Kong

Zhao

et al. 2022

Environ. Sci. Technol.

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The removal of arsenic (As(V) and As(III)) from strongly acidic wastewater using traditional neutralization or sulfuration precipitation methods produces a large amount of arsenic-containing hazardous wastes, which poses a potential threat to the environment. In this study, an ultraviolet/formic acid (UV/HCOOH) process was proposed to reductively remove and recover arsenic from strongly acidic wastewater in the form of valuable elemental arsenic (As(0)) products to avoid the generation of hazardous wastes. We found that more than 99% of As(V) and As(III) in wastewater was reduced to highly pure solid As(0) (>99.5 wt %) by HCOOH under UV irradiation. As(V) can be efficiently reduced to As(IV) (H2AsO3 or H4AsO4) by hydrogen radicals (H•) generated from the photolysis of HCOOH through dehydroxylation or hydrogenation. Then, As(IV) is reduced to As(III) by H• or through its disproportionation. The reduction of As(V) to H4AsO4 by H• and the disproportionation of H4AsO4 are the main reaction processes. Subsequently, As(III) is reduced to As(0) not only by H• through stepwise dehydroxylation but also through the disproportionation of intermediate arsenic species As(II) and As(I). With additional density functional theory calculations, this study provides a theoretical foundation for the reductive removal of arsenic from acidic wastewater.

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