Evaluation of the free energy of formation of Fe(II)-Fe(III) hydroxide-sulphate (green rust) and its reduction of nitrite

Hansen, Hans Christian Bruun; Borggaard, Ole K.; Sørensen, Jan

doi:10.1016/0016-7037(94)90131-7

Cited by 228 publications

(222 citation statements)

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“…Production of N 2 gas was adduced to the presence of the deposited metals on nZVI (Hosseini et al, 2011;Liou et al, 2009). N 2 O, a common product of nitrate reduction (Hansen et al, 1994;Fanning, 2000), may have also been produced in our experiments. In our study, the presence of Cd(II) caused gaseous products generation due to the increase in pH, since basic conditions are favorable for N 2 generation (Liou et al, 2009).…”

Section: Effect Of Cd(ii) On Gaseous Products Of Nitrate Reductionmentioning

confidence: 99%

Simultaneous removal of cadmium and nitrate in aqueous media by nanoscale zerovalent iron (nZVI) and Au doped nZVI particles

et al. 2014

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a b s t r a c tNanoscale zerovalent iron (nZVI) has demonstrated high efficacy for treating nitrate or cadmium (Cd) contamination, but its efficiency for simultaneous removal of nitrate and Cd has not been investigated. This study evaluated the reactivity of nZVI to the cocontaminants and by-product formation, employed different catalysts to reduce nitrite yield from nitrate, and examined the transformation of nZVI after reaction. Nitrate reduction resulted in high solution pH, negatively charged surface of nZVI, formation of Fe 3 O 4 (a stable transformation of nZVI), and no release of ionic iron. Increased pH and negative charge contributed to significant increase in Cd(II) removal capacity (from 40 mg/g to 188 mg/g) with nitrate present. In addition, nitrate reduction by nZVI could be catalyzed by Cd(II): while 30% of nitrate was reduced by nZVI within 2 h in the absence of Cd(II), complete nitrate reduction was observed in the presence of 40 mg-Cd/L due to the formation of Cd islands (Cd(0) and CdO) on the nZVI particles. While nitrate was reduced mostly to ammonium when Cd(II) was not present or at Cd(II) concentrations ! 40 mg/L, up to 20% of the initial nitrate was reduced to nitrite at Cd(II) concentrations < 40 mg/L. Among nZVI particles doped with 1 wt. % Cu, Ag, or Au, nZVI deposited with 1 wt. % Au reduced nitrite yield to less than 3% of the initial nitrate, while maintaining a high Cd(II) removal capacity.© 2014 Elsevier Ltd. All rights reserved. Available online at www.sciencedirect.com ScienceDirect journal homepage: www.else vier.com/locate /wa tres w a t e r r e s e a r c h 6 3 ( 2 0 1 4 ) 1 0 2 e1 1 1http://dx

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Section: Effect Of Cd(ii) On Gaseous Products Of Nitrate Reductionmentioning

confidence: 99%

Simultaneous removal of cadmium and nitrate in aqueous media by nanoscale zerovalent iron (nZVI) and Au doped nZVI particles

et al. 2014

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“…However, this is no easy task, due to the great amount of thermodynamic data required including standard free energies, enthalpies and entropies of formation for all the wide range of compositional variations of LDHs. Moreover, very few articles are found in the literature [78][79][80] dealing with all the necessary data to make this work feasible. We have recently proposed 81 and evaluated five different models for the estimation of thermodynamic properties of LDH compounds.…”

Section: Introductionmentioning

confidence: 99%

Review of the synthesis of layered double hydroxides: a thermodynamic approach

Bravo-Suárez¹,

Páez‐Mozo²,

Oyama³

2004

Quím. Nova

118

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Recebido em 29/4/03; aceito em 3/11/03; publicado na web em 27/05/04The synthesis of layered double hydroxides (LDHs) by hydrothermal-LDH reconstruction and coprecipitation methods is reviewed using a thermodynamic approach. A mixture model was used for the estimation of the thermodynamics of formation of LDHs. The synthesis and solubility of LDHs are discussed in terms of standard molar Gibbs free energy change of reaction. Data for numerous divalent and trivalent metals as well as for some monovalent and tetravalent metals that may be part of the LDH structure have been compiled. Good agreement is found between theoretical and experimental data. Diagrams and tables for the prediction of possible new LDH materials are provided.

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“…Green rusts (GRs) represent Fe(II)Fe(III)-hydroxides, which can lbrm in anoxic environments (Taylor, 1980;Hansen et al, 1994) and GR-like compounds have recently been identified in gley soils (Trolard et al, 1997). GRs belong to the pyroaurite-class of layered double metal hydroxides, LDHs (Bernal et al, 1959;Brindley and Bish, 1976).…”

Section: Introductionmentioning

confidence: 99%

Interaction of Synthetic Sulphate “Green Rust” with Phosphate and the Crystallization of Vivianite

Hansen¹

1999

Clays and clay miner.

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Abstract--Because layered Fe(II)Fe(III)-hydroxides (Green rusts, GRs) are anion exchangers, they represent potential orthophosphate sorbents in anoxic soils and sediments. To evaluate this possibility, two types of experiments with synthetic sulphate-interlayered GRs (GRso 4 = Fe2+4Fe3+a(OH)12SO 4 xH20 ) were studied. First, sorption of phosphate in GRso 4 was followed by reacting suspensions of pure GRso ~ synthesized by oxidation of Fe(II) with an excess of Na2HPO4 (pH 9.3). Second the possible incorporation of phosphate in GR during formation by Fe(II)-induced reductive dissolution of phosphate-containing ferrihydrites was examined in systems containing an excess of Fe(lI) (pH 7). With excess phosphate in solution, GRso ~ initially sorbed phosphate in the interlayer producing a basal layer spacing of 1.04 nm, but only --50% of the interlayer sulphate was exchanged with phosphate. This GR slowly transformed to vivianite within months. In the Fe(II)-rich systems, reaction with synthetic ferrihydrites produced GRso 4 similar to that produced by air oxidation. Reaction of Fe(II) with phosphate-containing ferrihydrites initially produced amorphous greenish phosphate containing precipitates which, after 3-4 h, crystallized to GRso 4 and vivianite. In these solutions, stable phosphate-free GRso 4 can form since precipitation of vivianite produced low phosphate activity. Consequently, in both systems GR or amorphous greenish precipitates act as reactive intermediates, but vivianite is the stable end-product limiting phosphate concentration in solution. It is also inferred that Fe(OH) 2 is an unlikely phosphate sorbent in mixed Fe(II)-Fe(III) systems because GR phases are more stable (less soluble) than Fe(OH)2.

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Evaluation of the free energy of formation of Fe(II)-Fe(III) hydroxide-sulphate (green rust) and its reduction of nitrite

Cited by 228 publications

References 53 publications

Simultaneous removal of cadmium and nitrate in aqueous media by nanoscale zerovalent iron (nZVI) and Au doped nZVI particles

Simultaneous removal of cadmium and nitrate in aqueous media by nanoscale zerovalent iron (nZVI) and Au doped nZVI particles

Review of the synthesis of layered double hydroxides: a thermodynamic approach

Interaction of Synthetic Sulphate “Green Rust” with Phosphate and the Crystallization of Vivianite

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