Voltammetric Characteristics of Hydrous Fe(III) Oxide Embedded into Nafion and Immobilised onto a Screen Printed Carbon Electrode: Binding of Arsenate versus Phosphate

Thulase Sivasothy, Nche George Ndifor-Angwafor , Frank Marken

Research output: Contribution to journalArticle

Abstract

Nafion offers microporous channels of typically 1-4 nm diameter for cation exchange. Recently, it has been shown that these cation exchanger properties can be inverted to allow anion binding by pre-filling the hydrophilic channel structure. Here, pre-filling is performed with hydrous iron oxide and sensitivity towards anionic phosphate and arsenate analytes is investigated. After a period of phosphate/arsenate accumulation, the voltammetric response in aqueous 1 M NaNO3 is obtained based on the Fe(III/II) redox process. The position of the peak at distinct potentials clearly reveals the presence of either phosphate or arsenate, presumably present in the form of FePO4 and FeAsO4. In the presence of mixtures of phosphate and arsenate, a competition of FePO4 versus FeAsO4 nucleation (within the Nafion microporous host) is suggested to result in a switch of phosphate detection at higher concentrations (> ca. 500 M, solubility controlled) towards arsenate detection at lower concentrations (< ca. 500 M, nucleation controlled). This phenomenon is suggested to be linked to the Ostwald step rule.
LanguageEnglish
JournalJournal of Solid State Electrochemistry
Early online date12 Jun 2018
DOIs
StatusE-pub ahead of print - 12 Jun 2018

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arsenates
Oxides
phosphates
Phosphates
Carbon
Electrodes
electrodes
oxides
carbon
Cations
Nucleation
Positive ions
nucleation
cations
exchangers
Ion exchangers
Iron oxides
iron oxides
Anions
low concentrations

Cite this

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title = "Voltammetric Characteristics of Hydrous Fe(III) Oxide Embedded into Nafion and Immobilised onto a Screen Printed Carbon Electrode: Binding of Arsenate versus Phosphate",
abstract = "Nafion offers microporous channels of typically 1-4 nm diameter for cation exchange. Recently, it has been shown that these cation exchanger properties can be inverted to allow anion binding by pre-filling the hydrophilic channel structure. Here, pre-filling is performed with hydrous iron oxide and sensitivity towards anionic phosphate and arsenate analytes is investigated. After a period of phosphate/arsenate accumulation, the voltammetric response in aqueous 1 M NaNO3 is obtained based on the Fe(III/II) redox process. The position of the peak at distinct potentials clearly reveals the presence of either phosphate or arsenate, presumably present in the form of FePO4 and FeAsO4. In the presence of mixtures of phosphate and arsenate, a competition of FePO4 versus FeAsO4 nucleation (within the Nafion microporous host) is suggested to result in a switch of phosphate detection at higher concentrations (> ca. 500 M, solubility controlled) towards arsenate detection at lower concentrations (< ca. 500 M, nucleation controlled). This phenomenon is suggested to be linked to the Ostwald step rule.",
author = "Thulase Sivasothy and Ndifor-Angwafor, {Nche George} and Frank Marken",
year = "2018",
month = "6",
day = "12",
doi = "10.1007/s10008-018-4009-9",
language = "English",
journal = "Journal of Solid State Electrochemistry",
issn = "1432-8488",
publisher = "Springer Verlag",

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TY - JOUR

T1 - Voltammetric Characteristics of Hydrous Fe(III) Oxide Embedded into Nafion and Immobilised onto a Screen Printed Carbon Electrode: Binding of Arsenate versus Phosphate

AU - Sivasothy, Thulase

AU - Ndifor-Angwafor , Nche George

AU - Marken, Frank

PY - 2018/6/12

Y1 - 2018/6/12

N2 - Nafion offers microporous channels of typically 1-4 nm diameter for cation exchange. Recently, it has been shown that these cation exchanger properties can be inverted to allow anion binding by pre-filling the hydrophilic channel structure. Here, pre-filling is performed with hydrous iron oxide and sensitivity towards anionic phosphate and arsenate analytes is investigated. After a period of phosphate/arsenate accumulation, the voltammetric response in aqueous 1 M NaNO3 is obtained based on the Fe(III/II) redox process. The position of the peak at distinct potentials clearly reveals the presence of either phosphate or arsenate, presumably present in the form of FePO4 and FeAsO4. In the presence of mixtures of phosphate and arsenate, a competition of FePO4 versus FeAsO4 nucleation (within the Nafion microporous host) is suggested to result in a switch of phosphate detection at higher concentrations (> ca. 500 M, solubility controlled) towards arsenate detection at lower concentrations (< ca. 500 M, nucleation controlled). This phenomenon is suggested to be linked to the Ostwald step rule.

AB - Nafion offers microporous channels of typically 1-4 nm diameter for cation exchange. Recently, it has been shown that these cation exchanger properties can be inverted to allow anion binding by pre-filling the hydrophilic channel structure. Here, pre-filling is performed with hydrous iron oxide and sensitivity towards anionic phosphate and arsenate analytes is investigated. After a period of phosphate/arsenate accumulation, the voltammetric response in aqueous 1 M NaNO3 is obtained based on the Fe(III/II) redox process. The position of the peak at distinct potentials clearly reveals the presence of either phosphate or arsenate, presumably present in the form of FePO4 and FeAsO4. In the presence of mixtures of phosphate and arsenate, a competition of FePO4 versus FeAsO4 nucleation (within the Nafion microporous host) is suggested to result in a switch of phosphate detection at higher concentrations (> ca. 500 M, solubility controlled) towards arsenate detection at lower concentrations (< ca. 500 M, nucleation controlled). This phenomenon is suggested to be linked to the Ostwald step rule.

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