Thermodynamic properties of FeAsO4 center dot 0.75H(2)O - a more favorable disposable product of low As solubility

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11310%2F16%3A10331696" target="_blank" >RIV/00216208:11310/16:10331696 - isvavai.cz</a>

Result on the web

<a href="http://dx.doi.org/10.1016/j.hydromet.2016.05.019" target="_blank" >http://dx.doi.org/10.1016/j.hydromet.2016.05.019</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.hydromet.2016.05.019" target="_blank" >10.1016/j.hydromet.2016.05.019</a>

Result language

angličtina

Original language name

Thermodynamic properties of FeAsO4 center dot 0.75H(2)O - a more favorable disposable product of low As solubility

Original language description

In this work, we determined the full set of thermodynamic properties for the ferric orthoarsenate, FeAsO4 center dot 0.75H(2)O. This phase could be expected in metallurgical waste forms from pressure oxidation of arsenopyrite-rich ores and its solubility is therefore of interest for the understanding of arsenic mobility in such waste forms. Using a combination of solubility experiments at low pH (<2) and relaxation calorimetry, we have determined log K-sp of -26.54 +/- 0.35 for the reaction FeAsO4 center dot 0.75H(2)O = Fe3+ + AsO43- + 0.75H(2)O and S-0 for the ferric orthoarsenate of 154.2 +/- 0.5 J mol(-1) K-1, respectively. These data give Delta(f)G(0) (FeAsO4 center dot 0.75H(2)O) = -993.15 +/- 2.57 kJ mol(-1) and Delta H-f(0) (FeAsO4 center dot 0.75H(2)O) = -114038 +/- 2.59 kJ mol(-1). The calculated enthalpy was checked by thermodynamic considerations of the system FeAsO4-H2O and found in a good agreement with the expected value. Heat capacity at temperatures higher than the ambient ones was fit by a Berman-Brown polynomial C-p = k(0) + k(1)T(-0.5) + k(2)T(-2) + k(3)T(-3) with the coefficients k(0) = 1.774 x 10(2), k(1)= 6.531 x 10(2), k(2) = -1.265 x 10(7), and k(3) = 1.754 x 10(9) (fit valid between 280 and 465 K). Ferric orthoarsenate is less soluble than scorodite (FeAsO4 center dot 0.75H(2)O) and could be thus an interesting alternative for the disposal of arsenical waste. Its use will be certainly hampered by the high temperature required for its synthesis (>200 degrees C). One could, however, attempt to tweak the pressure oxidation technology such that the formation of ferric orthoarsenate would be enhanced, hence producing a waste form with relatively low arsenic solubility.

Czech name

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Czech description

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Type

J_x - Unclassified - Peer-reviewed scientific article (Jimp, Jsc and Jost)

CEP classification

DD - Geochemistry

OECD FORD branch

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Project

<a href="/en/project/GC13-01706J" target="_blank" >GC13-01706J: Arsenic speciation in mining wastes ? case studies in systems dominated by ferric sulfo-arsenates</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2016

Confidentiality

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

Name of the periodical

Hydrometallurgy

ISSN

0304-386X

e-ISSN

—

Volume of the periodical

164

Issue of the periodical within the volume

SEPTEMBER

Country of publishing house

NL - THE KINGDOM OF THE NETHERLANDS

Number of pages

5

Pages from-to

136-140

UT code for WoS article

000381949900019

EID of the result in the Scopus database

2-s2.0-84976363273