The mechanisms of reduction of hexavalent chromium by green rust sodium sulphate: Formation of Cr-goethite

Skovbjerg, L.L.; Stipp, S. L. S.; Utsunomiya, Satoshi; Ewing, Rodney C.

doi:10.1016/j.gca.2006.02.017

Cited by 120 publications

(117 citation statements)

References 21 publications

(46 reference statements)

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“…Fe(II)-Fe(III) hydroxysalt green rust (GR) compounds belong to the layered double hydroxide (LDH) family and obey the general chemical formula [Fe(II) (1−x) Fe(III) x OH) 2 ] x+ [(x/n)A n− mH 2 O] x− where A n− is an intercalated anion, e.g. Cl − , SO 4 2− , CO 3 2− , and x is the Fe(III) molar fraction [Fe(III)]/[Fe (total) ] of the positively charged hydroxide sheets.…”

Section: Introductionmentioning

confidence: 99%

“…The redox flexibility of GR facilitates a key role in the corrosion of iron-based materials, environmental science and technology. It has then been extensively studied as a reductant pool for inorganic oxyanions such as nitrates [1] and toxic metal species including chromate [2] and selenate. [3] Therefore, GR coated sand may serve as promising material in reactive filtration processes for the purification of waste/polluted water.…”

Section: Introductionmentioning

confidence: 99%

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XPS study of Fe(II)Fe(III) (oxy)hydroxycarbonate green rust compounds

Mullet

Khare

Ruby

2008

Surface & Interface Analysis

174

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

XPS study of Fe(II)Fe(III) (oxy)hydroxycarbonate green rust compounds

Mullet

Khare

Ruby

2008

Surface & Interface Analysis

174

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“…In the presence of sufficient amounts of chromate, the oxidation of ferrous phases may also involve the reduction of chromate, and the potential at the cathode remains low even in the presence of hypochlorite. It has been shown that chromium (III) species formed on the surface by subsequent oxidation of the ferrous iron inhibits the further oxidation of ferrous oxide [45]. This observation might explain the formation of green rust and the high amount of chromium found in the EDX analysis.…”

Section: Surface Characterisationmentioning

confidence: 99%

“…5b. Green rust products form by gentle oxidation of ferrous phases and are characterised by a crystal structure consisting of stacked brucite-like layers of Fe(OH) 6 octahedrons carrying positive charges and interlayers of anions and water molecules that restore the electroneutrality of the whole structure [41][42][43][44][45][46][47].…”

Section: Surface Characterisationmentioning

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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“…For instance, Cr 6+ may transform into Cr 3+ , Se 6+ into Se 4+ or As 5+ into As 3+ [1][2][3][4][5][6][7]. One most outstanding example is that of nitrates which can be reduced into nitrogen that escapes without harming the environment in the atmosphere.…”

Section: Introductionmentioning

confidence: 99%