Thermodynamic properties of scorodite and parascorodite (FeAsO4 center dot 2H(2)O), kankite (FeAsO4 center dot 3.5H(2)O), and FeAsO4

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216224%3A14310%2F12%3A00107089" target="_blank" >RIV/00216224:14310/12:00107089 - isvavai.cz</a>

Alternative codes found

RIV/67985831:_____/12:00377319 RIV/00216208:11310/12:10126479

Result on the web

<a href="https://www.sciencedirect.com/science/article/pii/S0304386X12000291" target="_blank" >https://www.sciencedirect.com/science/article/pii/S0304386X12000291</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.hydromet.2012.02.002" target="_blank" >10.1016/j.hydromet.2012.02.002</a>

Result language

angličtina

Original language name

Thermodynamic properties of scorodite and parascorodite (FeAsO4 center dot 2H(2)O), kankite (FeAsO4 center dot 3.5H(2)O), and FeAsO4

Original language description

Iron arsenates, either well or poorly crystalline, are the usual phases of choice for arsenic immobilization in waste forms of variable origin. Among these phases. scorodite (FeAsO4 center dot 2H(2)O) is used very often because of its favorable properties. The thermodynamic properties of this phase, necessary for the prediction of its dissolution or precipitation, have been usually constrained by solubility experiments. Here, we measured the thermodynamic properties of scorodite, its polymorph parascorodite, the mineral kafikite (FeAsO4 center dot 35H(2)O), and the anhydrous FeAsO4 by a combination of calorimetric techniques, thus avoiding the inherent uncertainties of the solubility experiments. The enthalpies of formation from elements at standard temperature and pressure for scorodite, parascorodite, kankite, and FeAsO4 are -1508.9 +/- 2.9, -1506.6 +/- 2.9, -1940.2 +/- 2.8, and -899.0 +/- 3.0 kJ.mol(-1), respectively. The measured standard entropies for scorodite and kafikite are 188.0 +/- 2.1 and 247.6 +/- 2.8J.mol(-1). K-1, respectively; entropies of FeAsO4 and parascorodite were estimated. The resulting Gibbs free energies of formation for scorodite, parascorodite, karikite, and FeAsO4 are -1284.8 +/- 2.9, -1282.5, -1629.6 +/- 2.9. and -786.7 kJ.mol(-1), respectively. The solubility product for scorodite of -25.83 +/- 0.52 is in an excellent agreement with a previously selected best value of -25.83 +/- 0.07 from Langmuir et al. (2006). As expected, scorodite is stable under a wide range of conditions applicable to terrestrial surface environments. The anhydrous FeAsO4, parascorodite, and kankite are either metastable or stable under restricted conditions which are unlikely for the terrestrial surface environments. Using the thermodynamic data for scorodite and for a suite of ferric oxides, we can predict the aqueous As concentrations in systems in which scorodite dissolves and ferric oxides precipitate. These models show that the As concentration can vary widely as function of the nature, chemical composition, and crystallinity of these ferric oxides.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

20501 - Materials engineering

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2012

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Hydrometallurgy

ISSN

0304-386X

e-ISSN

1879-1158

Volume of the periodical

117

Issue of the periodical within the volume

APR

Country of publishing house

NL - THE KINGDOM OF THE NETHERLANDS

Number of pages

10

Pages from-to

47-56

UT code for WoS article

000303486500007

EID of the result in the Scopus database

2-s2.0-84859426036