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Galena Oxidation in Oxygen-Bearing Acidic Solutions
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2019-11-04 , DOI: 10.1021/acsearthspacechem.9b00190
Paul Chiriţă 1
Affiliation  

The oxidation of galena (PbS) by oxygen-bearing acidic solutions was investigated over the pH range of 2–3.5 at two different oxygen concentrations (7.0 × 10–5 and 2.2 × 10–4 M) and a temperature of 25 °C using a potentiodynamic polarization technique, electrochemical impedance spectroscopy (EIS), aqueous batch experiments, and Fourier transforms infrared spectroscopy. EIS results indicate that the aqueous oxidation of galena is controlled by a surface reaction. At 25 °C and [O2] = 2.2 × 10–4 M, the reaction order with respect to the proton concentration is virtually zero (nH = −0.02 ± 0.08), indicating that hydrogen is not involved in the rate-determining step of the reaction. At pH 2 and 25 °C, the reaction order with respect to the oxygen concentration is 0.96 ± 0.06, showing that oxygen is an important component of the activated complex. The experimental results can be reasonably explained by the mixed potential theory. The aqueous oxidation rates evaluated by electrochemical measurements are not affected by the non-oxidative dissolution or the solid phases precipitated on the mineral surface and offer reliable information for the understanding of lead and sulfur mobility in the environment.

中文翻译:

含氧酸性溶液中的方铅矿氧化

在两种不同的氧气浓度(7.0×10 –5和2.2×10 –4 M)和温度为25°C的情况下,在2–3.5的pH范围内,研究了含氧酸性溶液对方铅矿(PbS)的氧化电位动力学极化技术,电化学阻抗谱(EIS),水性间歇实验和傅里叶变换红外光谱。EIS结果表明方铅矿的水氧化受表面反应控制。在25°C且[O 2 ] = 2.2×10 –4 M时,相对于质子浓度的反应阶数实际上为零(n H= -0.02±0.08),表明氢不参与反应的速率确定步骤。在pH 2和25°C下,相对于氧浓度的反应顺序为0.96±0.06,这表明氧是活化配合物的重要成分。实验结果可以用混合势理论合理地解释。通过电化学测量评估的水氧化速率不受非氧化溶解或沉淀在矿物表面上的固相的影响,并为理解环境中的铅和硫迁移率提供了可靠的信息。
更新日期:2019-11-04
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