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

Kód výsledku v 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>

Nalezeny alternativní kódy

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

Výsledek na webu

<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>

Jazyk výsledku

angličtina

Název v původním jazyce

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

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

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

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

20501 - Materials engineering

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2012

Kód důvěrnosti údajů

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

Název periodika

Hydrometallurgy

ISSN

0304-386X

e-ISSN

1879-1158

Svazek periodika

117

Číslo periodika v rámci svazku

APR

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

10

Strana od-do

47-56

Kód UT WoS článku

000303486500007

EID výsledku v databázi Scopus

2-s2.0-84859426036