Solubilities of synthetic schwertmannite and ferrihydrite
Solubilities of synthetic schwertmannite and ferrihydrite
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合成施威特曼石和水铁矿的溶解度
DOI：
10.2343/geochemj.36.119
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发表时间：
2002
影响因子：
0.8
通讯作者：
Jinhwan Kim
中科院分区：
文献类型：
--
作者：
Jae;Misun Park;Jinhwan Kim
在实验室中在25°C下合成施威特曼石、2线水铁矿和6线水铁矿以测定它们的溶解度。合成矿物的化学分析和热分析表明，水铁矿的化学式为Fe 2 O3-x（SO 4）x·nH 2 O（0.41 ≤ x ≤ 0.49，1.51 ≤ n ≤ 2.81），水铁矿Fe 2 O3 -0.5y（OH）y·nH 2 O（0 ≤ y ≤ 1.96，0.82 ≤ n ≤ 1.14）。用PHREEQC程序计算了各矿物的活度，计算了各矿物的溶度积（K）。估计的log K值为2.01 ± 0.30的施氏石，8.46 ± 1.40的2线的水铁矿，和10.12 ± 0.74的6线的水铁矿。施氏石的溶解度似乎取决于硫酸盐含量，但需要更多的研究来量化这种关系。水铁矿的溶解度与水含量之间没有明显的相关性。在本研究中预测的施氏铁矿和水铁矿之间的稳定性边界偏向于比自然界中观察到的更高的pH，这也需要进一步研究。
Schwertmannite, 2-line ferrihydrite, and 6-line ferrihydrite were synthesized at 25°C in the laboratory to determine their solubilities. Chemical and thermal analyses of the synthesized minerals show that schwertmannite has the chemical formula Fe2O3-x(SO4)x·nH2O (0.41 ≤ x ≤ 0.49, 1.51 ≤ n ≤ 2.81) and ferrihydrite Fe2O3-0.5y(OH)y·nH2O (0 ≤ y ≤ 1.96, 0.82 ≤ n ≤ 1.14). The solubility products (K) of the minerals were estimated from the activities of the corresponding species calculated with the computer program PHREEQC. The estimated log K values are 2.01 ± 0.30 for schwertmannite, 8.46 ± 1.40 for 2-line ferrihydrite, and 10.12 ± 0.74 for 6-line ferrihydrite. The solubility of schwertmannite seems to vary depending on the sulfate content, but more investigation is needed to quantify the relationship. The solubility of ferrihydrite does not show any significant correlation with the water content. The stability boundary between schwertmannite and ferrihydrite predicted in this study is biased to higher pH than that observed in nature, which also need further investigation.