Cathodic Reactions on an Iron RDE in the Presence of Y(III)

Nylén, Linda; Gustavsson, John; Cornell, Ann

doi:10.1149/1.2958299

Cited by 15 publications

(15 citation statements)

References 18 publications

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“…However, experiments with Y(NO 3 ) 3 addition may be hard to interpret due to the difficulty in separating nitrate reduction from hydrogen evolution [19]. Therefore we [19] confirmed the activation of the HER from water in nitrate-free 0.5 M chloride solutions. Thus, the Y(III) addition activates hydrogen evolution from water, reaction 5, while hindering hydrogen evolution from protons, reaction 10.…”

Section: Effects Of Electrolyte Additions Of Rare Earth Metal (Rem) Ionssupporting

confidence: 61%

“…In a previous study, we found that addition of yttrium chloride salt to 0.5 M NaCl solutions at 25°C hinders not only oxygen reduction (reaction 8), but also the reduction of hypochlorite, nitrate and protons (reactions 6, 9, 10) on iron cathodes [19]:…”

Section: Effects Of Electrolyte Additions Of Rare Earth Metal (Rem) Ionsmentioning

confidence: 92%

“…The activating effect on HER of Y(III) and inhibition of nitrate reduction, hypochlorite reduction and proton reduction has earlier been investigated at 25°C and 0.5 M Cl [19]. In the present study we approach conditions more relevant for the chlorate process, i.e.…”

Section: Effects Of Electrolyte Additions Of Rare Earth Metal (Rem) Ionsmentioning

confidence: 99%

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Rare earth metal salts as potential alternatives to Cr(VI) in the chlorate process

2010

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Chromate is today added to industrial chlorate electrolyte, where it forms a thin cathode film of chromium hydroxide that hinders unwanted reduction of hypochlorite and chlorate. The aim of this study was to investigate rare earth metal (REM) ions as an environmentally friendly alternative to the toxic chromate addition. Potential sweeps and iR-corrected polarisation curves were recorded using rotating disc electrodes of iron and gold. Addition of Y(III), La(III) or Sm(III) to 5 M NaCl at 70°C suppressed hypochlorite reduction. Activation of hydrogen evolution by REM ion addition to 0.5 M NaCl was more significant at 25°C than at 50 and 70°C. Increasing the chloride concentration to 5 M had a detrimental effect on this activation. The major problem in replacing chromate with REM salts is the poor solubility of REM ions at normal chlorate process conditions, and therefore REM salts are not a realistic alternative to chromate addition.

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Section: Effects Of Electrolyte Additions Of Rare Earth Metal (Rem) Ionssupporting

confidence: 61%

Section: Effects Of Electrolyte Additions Of Rare Earth Metal (Rem) Ionsmentioning

confidence: 92%

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Rare earth metal salts as potential alternatives to Cr(VI) in the chlorate process

2010

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“…Rare earth metal salts presented promising results in bench-scale experiments [24][25][26], but their solubility in a chlorate electrolyte [24] and/or low efficiency in long-term experiments [26] limit their application in real processes. Another option is the use of molybdate in the electrolyte.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Investigation of the Hydrogen Evolution Reaction on Electrodeposited Films of Cr(OH)3 and Cr2O3 in Mild Alkaline Solutions

et al. 2017

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The hydrogen evolution reaction (HER) from water reduction is the main cathodic reaction in the sodium chlorate process. The reaction typically takes place on electrodes covered with a Cr(III) oxide-like film formed in situ by reduction of sodium dichromate in order to avoid reduction of hypochlorite and thereby increase the selectivity for the HER. However, the chemical structure of the Cr(III) oxide-like film is still under debate. In the present work, the kinetics of the HER were studied using titanium electrodes covered with electrodeposited Cr(OH) 3 or Cr 2 O 3 , which were characterized by means of scanning electron microscopy (SEM), energydispersive x-ray spectroscopy (EDX), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. A clear difference in the morphology of the deposited surfaces was obtained, and the structure could be revealed with Raman spectroscopy. The kinetics for the HER were investigated using potentiodynamic and potentiostatic techniques. The results show that the first electron transfer is rate limiting and that the activity decreases in the order Cr 2 O 3 @Ti > bare Ti > Cr(OH) 3 @Ti. The low activity obtained for Cr(OH) 3 @Ti is discussed in terms of the involvement of structural water in the HER and the slow ligand exchange rate for water in Cr(III) complexes, while the high activity obtained for Cr 2 O 3 @Ti is rationalized by a surface area effect in combination with reduction of surface water and water in solution.

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“…The current efficiency has been studied in some publications, but the most common approach is to study the cell or electrode potential and oxygen production [9,10,[12][13][14][15][16][17]. It has also been reported that the time it takes to reach stable conditions in a chlorate cell or at the surface of a chlorate cathode is significantly long [8].…”

Section: Introductionmentioning

confidence: 99%

Current efficiency of individual electrodes in the sodium chlorate process: a pilot plant study

et al. 2017

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Current efficiency in the sodium chlorate process is a key issue in the evaluation of the power consumption. A pilot cell unit for executing the sodium chlorate process was constructed to study the current efficiency of the anode and cathode separately. The effects of sodium dichromate and sodium sulphate concentrations and the electrolyte temperature on the anode and cathode current efficiencies were studied. Corrosion products formed on the mild steel cathodes after their removal from the cell were characterised using X-ray diffraction and infrared spectroscopy. The results show that the cathodic current efficiency increases with increasing dichromate concentrations in the electrolyte until approximately 5 g dm -3 is reached. At this optimum concentration of dichromate, the presence of sulphate ions decreases the cathodic current efficiency. For moderate increases in temperature, the cathodic current efficiency increases, but oxygen evolution is promoted, and the power consumption also increases. Surface characterisation of the electrodes after their exposure to air shows two primary types of behaviour, depending on the process parameters. At low dichromate concentrations, amorphous corrosion layers are formed, while at higher concentrations, reduced forms of iron hydroxides, i.e., ''green rust'', are identified. Although the electrodes were positioned at the open circuit potential for 40 min before their removal from the cell, chromium remains on the cathode surface. This result might explain the corrosion-inhibiting effect of the addition of chromate to the electrolyte. The results from this study can be used to optimise operating procedures in real plants, decrease the energy consumption and minimise the environmental impact of these processes.Electronic supplementary material The online version of this article

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Cathodic Reactions on an Iron RDE in the Presence of Y(III)

Cited by 15 publications

References 18 publications

Rare earth metal salts as potential alternatives to Cr(VI) in the chlorate process

Rare earth metal salts as potential alternatives to Cr(VI) in the chlorate process

Electrochemical Investigation of the Hydrogen Evolution Reaction on Electrodeposited Films of Cr(OH)3 and Cr2O3 in Mild Alkaline Solutions

Current efficiency of individual electrodes in the sodium chlorate process: a pilot plant study

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