Flow anodic oxidation: Towards high-efficiency removal of aqueous contaminants by adsorbed hydroxyl radicals at 1.5 V vs SHE

Xie, Jiangzhou; Ma, Jinxing; Zhao, Shixin; Waite, T. David

doi:10.1016/j.watres.2021.117259

Cited by 43 publications

(29 citation statements)

References 69 publications

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“…At present, plate-in-tank reactors are the most commonly used reactor type in lab-scale experiments, though suspension or flow electrode systems are emerging as an attractive alternative electrochemical cell architecture, with advantages of relatively low energy consumption, effective electron transfer, and the feasibility of continuous long-term operation. − Although some progress has been achieved in the development and use of flow anodic oxidation processes, , to the best of our knowledge, there has been no investigation of the reduction process using flow cathodes. Here, we investigate electrochemical reduction of nitrate in a flow cathode system in which flowable low-cost copper-modified carbon particles (Cu@AC) act as mobile cathodes, and Ir-Ta meshes serve as the current collectors in the anode and cathode chambers.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Reduction of Nitrate with Simultaneous Ammonia Recovery Using a Flow Cathode Reactor

Sun

Garg

Xie

et al. 2022

Environ. Sci. Technol.

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The presence of excessive concentrations of nitrate in industrial wastewaters, agricultural runoff, and some groundwaters constitutes a serious issue for both environmental and human health. As a result, there is considerable interest in the possibility of converting nitrate to the valuable product ammonia by electrochemical means. In this work, we demonstrate the efficacy of a novel flow cathode system coupled with ammonia stripping for effective nitrate removal and ammonia generation and recovery. A copper-loaded activated carbon slurry (Cu@AC), made by a simple, low-cost wet impregnation method, is used as the flow cathode in this novel electrochemical reactor. Use of a 3 wt % Cu@AC suspension at an applied current density of 20 mA cm −2 resulted in almost complete nitrate removal, with 97% of the nitrate reduced to ammonia and 70% of the ammonia recovered in the acid-receiving chamber. A mathematical kinetic model was developed that satisfactorily describes the kinetics and mechanism of the overall nitrate electroreduction process. Minimal loss of Cu to solution and maintenance of nitrate removal performance over extended use of Cu@AC flow electrode augers well for long-term use of this technology. Overall, this study sheds light on an efficient, low-cost water treatment technology for simultaneous nitrate removal and ammonia generation and recovery.

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Section: Introductionmentioning

confidence: 99%

Electrochemical Reduction of Nitrate with Simultaneous Ammonia Recovery Using a Flow Cathode Reactor

Sun

Garg

Xie

et al. 2022

Environ. Sci. Technol.

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“…The signals of singlet oxygen ( 1 O 2 ) were also observed in electrolysis ( E ), E/PDS, and E/PDS/CNT systems (Figure S4b). Alcohols such as tert -butyl alcohol (TBA) and methanol (MeOH) are used as quenchers for radicals in the bulk solution or on the catalyst surface. − Despite this, KI is an effective scavenger of SBRs, , KI would react with persulfate ions as a reducing agent, and thus cannot be directly used in persulfate systems . As shown in Figure S5, radical quenchers, that is, methanol (MeOH) and TBA, as well as the singlet oxygen scavenger (TEMP) had a trivial impact on DCP degradation in either E/PDS/CNT or PDS/CNT systems, implying that radicals and singlet oxygen were not the primary ROS for DCP degradation.…”

Section: Resultsmentioning

confidence: 99%

Electro-Induced Carbon Nanotube Discrete Electrodes for Sustainable Persulfate Activation

Ren

Zhang

Cheng

et al. 2022

Environ. Sci. Technol.

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In electrochemical advanced oxidation processes (EAOPs), the rate-limiting step is the mass transfer of pollutants to the electrodes due to the limited active surface areas. To this end, we established a three-dimensional (3D) EAOP system by coupling conventional graphite electrodes with dispersed carbon nanotubes (CNTs). The electrodes (particularly the anode) induced electric field spontaneously polarized CNTs into dispersed reactive particle electrodes (CNT-PEs) in the solution, which remarkably promoted electrochemical activation of peroxydisulfate (PDS) to generate surface CNT–PDS* complexes and surface-bound radicals (SBRs). Based on the excited potential (E CNT‑PEs) at different positions in the 3D electric field, CNT-PEs were activated into three states. (i) E CNT‑PEs < E organic, CNT-PEs are chemically inert toward DCP oxidation; (ii) E organic < E CNT‑PEs < E water, CNT-PEs will oxidize DCP via an electron-transfer process (ETP); (iii) E CNT‑PEs > E water, both CNT–PDS* complexes and the anode will oxidize water to produce SBRs. Thus, DCP could be oxidized by CNT–PDS* complexes via ETP to form polychlorophenols on the CNT surface, causing rapid deactivation of the micro-electrodes. In contrast, SBRs attack DCP directly into chloride ions and hydroxylated products, maintaining the surface cleanliness and activity of CNT-PEs for long-term operations.

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“…Electrically charged or electrochemically reactive membranes (ERMs) integrate electrochemical advanced oxidation and/or electrochemical reduction reactions into membrane filtration to enhance pollutant degradation, rejection, or transformation (e.g., nitrification). , Electrochemical membrane filtration has demonstrated promising concurrent rejection and degradation of diverse contaminants for water purification and wastewater treatment . For example, effective removal of persistent organic pollutants (e.g., polycyclic aromatic hydrocarbons and polychlorinated biphenyls), dyes, pharmaceutical residuals, and personal care products, and perfluorochemicals as well as microbial species were reported. − In a typical configuration, the constituents of influent serve as the electrolyte, and ERMs act in the dual function of separation unit and electrode.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Aging and Halogen Oxides Formation on Multiwalled Carbon Nanotubes and Fe₃O₄@g-C₃N₄ Coated Conductive Membranes

Gao

Potts

et al. 2022

Ind. Eng. Chem. Res.

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Electrochemical membrane filtration is widely reported to enhance water contaminants’ degradation or rejection via anodic oxidation or cathodic repulsion. Despite their advances, electrochemical membranes or electrocatalysts often suffer from corrosion or passivation, especially under strong electrode potentials or reactions. Moreover, the formation of toxic byproducts, such as chlorinated organic compounds and oxyhalides (e.g., ClO4 –) is another major concern. This study investigated the membrane aging processes of two types of conductive membranes, multiwalled carbon nanotubes (MWCNTs) and ferrite/graphitic carbon nitride hybrids (Fe3O4@g-C3N4) coated on ceramic membranes. Under high current densities (∼20 mA·cm–2) with anodic potentials (∼10 V), MWCNTs and Fe3O4@g-C3N4 catalysts underwent evident oxidation as indicated by an increase of the intensity ratio of the Raman spectral bands (I D/I G) and charge transfer resistance (R ct) of two electrochemical membranes. Under variations of electrode potentials, chloride or bromide were shown to be oxidized to bromate (BrO3 –) and chlorate (ClO3 –) at levels of 1–10 mmol·L–1. The formation of BrO3 – and ClO3 – was dependent on the solution pH, current densities (1–20 mA·cm–2), and initial concentrations of Br or Cl ions. To warrant a safe and rational design and operation of electrochemically reactive membrane processes, membrane aging and toxic byproduct’s formation deserve careful characterization under relevant water filtration environments.

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Flow anodic oxidation: Towards high-efficiency removal of aqueous contaminants by adsorbed hydroxyl radicals at 1.5 V vs SHE

Cited by 43 publications

References 69 publications

Electrochemical Reduction of Nitrate with Simultaneous Ammonia Recovery Using a Flow Cathode Reactor

Electrochemical Reduction of Nitrate with Simultaneous Ammonia Recovery Using a Flow Cathode Reactor

Electro-Induced Carbon Nanotube Discrete Electrodes for Sustainable Persulfate Activation

Electrochemical Aging and Halogen Oxides Formation on Multiwalled Carbon Nanotubes and Fe₃O₄@g-C₃N₄ Coated Conductive Membranes

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Flow anodic oxidation: Towards high-efficiency removal of aqueous contaminants by adsorbed hydroxyl radicals at 1.5 V vs SHE

Cited by 43 publications

References 69 publications

Electrochemical Reduction of Nitrate with Simultaneous Ammonia Recovery Using a Flow Cathode Reactor

Electrochemical Reduction of Nitrate with Simultaneous Ammonia Recovery Using a Flow Cathode Reactor

Electro-Induced Carbon Nanotube Discrete Electrodes for Sustainable Persulfate Activation

Electrochemical Aging and Halogen Oxides Formation on Multiwalled Carbon Nanotubes and Fe3O4@g-C3N4 Coated Conductive Membranes

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Product

Resources

About

Electrochemical Aging and Halogen Oxides Formation on Multiwalled Carbon Nanotubes and Fe₃O₄@g-C₃N₄ Coated Conductive Membranes