Abstract The dissolution of biotite, a trioctahedral mica, was investigated for a temperature range of 25–70 °C and a pH range of 1–3 in the presence of HNO3 (nitric acid) and H2C2O4 (oxalic acid) solutions. Single millimetric, cleaved flakes of biotite were reacted in batch and flow-through experiments to obtain kinetic information and elucidate the mechanisms that control the overall dissolution reaction under these conditions. The reacting basal surface was explored using in-situ laser confocal microscopy (LCM-DIM) and ex-situ scanning and phase shifting interferometry (VSI-PSI), while the release of tetrahedral (Al and Si), octahedral (Mg and Fe) and exchange (K) cations in solution was monitored over time. This experimental approach allowed us to calculate far-from-equilibrium dissolution rates associated with changes in topography of the (001) surface (horizontal retreat (Rstep) and vertical retreat (Rvertical)), etch pit formation and growth (Rpit) and the release of Si in solution, i.e., bulk dissolution (Rbulk,Si). In HNO3 solutions, a proton promoted reaction mechanism (PPRM), through proton adsorption on the biotite surface, was dominant. The variation of Rstep, Rvertical and Rbulk,Si accounting for the dissolution of (hk0) surfaces at different temperature and pH was used to calculate the apparent activation energy (Ea) and the proton reaction order (nH+). The respective values decreased from 63 kJ mol−1 at pH 1 to 31 kJ mol−1 at pH 3 and increased from 0.46 at 25 °C to 0.77 at 70 °C. This variability was related to the variation of proton consumption with temperature. In H2C2O4 solutions, formation and growth of etch pits on the (001) surface occurred, yielding an increase in surface roughening. Rpit accounted for the rate of etch pit development which was observed to increase, as temperature increased. Based on Rpit, relatively high Ea values (121 kJ mol−1 and 162 kJ mol−1) were associated with an early evolution of the basal etch pits, whereas lower values (36 kJ mol−1 and 56 kJ mol−1) were calculated using Rbulk,Si. The present study contributes to the interpretation of the mechanisms involved in the biotite dissolution process at highly acidic pH, in the presence of inorganic and organic acid, and low temperature (T ≤ 80 °C). Furthermore, our results highlight the importance of combining surface and bulk analyses to assess the balance between the different reactions involving proton consumption during the dissolution and its dependency on temperature, pH and organic acids concentration.

中文翻译：

---

在低温和酸性 pH 条件下，黑云母在硝酸和草酸中的反应性来自表面和本体溶解测量

摘要 在 HNO3（硝酸）和 H2C2O4（草酸）溶液存在下，研究了黑云母（一种三八面体云母）在 25-70°C 的温度范围和 1-3 的 pH 值范围内的溶解。单毫米的黑云母裂解片在分批和流通实验中反应，以获得动力学信息并阐明在这些条件下控制整体溶解反应的机制。使用原位激光共聚焦显微镜 (LCM-DIM) 和非原位扫描和相移干涉仪 (VSI-PSI) 探索反应基底表面，同时释放四面体（Al 和 Si）、八面体（Mg 和 Fe）随着时间的推移监测溶液中的交换 (K) 阳离子。这种实验方法使我们能够计算与 (001) 表面形貌变化（水平后退 (Rstep) 和垂直后退 (Rvertical)）、蚀刻坑的形成和增长 (Rpit) 以及释放相关的远离平衡的溶解速率。 Si 在溶液中的溶解，即本体溶解 (Rbulk,Si)。在 HNO3 溶液中，质子促进反应机制 (PPRM)，通过质子吸附在黑云母表面，占主导地位。Rstep, Rvertical 和 Rbulk,Si 的变化考虑了 (hk0) 表面在不同温度和 pH 值下的溶解，用于计算表观活化能 (Ea) 和质子反应级数 (nH+)。各自的值从 pH 1 时的 63 kJ mol-1 降低到 pH 3 时的 31 kJ mol-1，并从 25 °C 时的 0.46 增加到 70 °C 时的 0.77。这种可变性与质子消耗随温度的变化有关。在 H2C2O4 溶液中，(001) 表面蚀刻坑的形成和生长发生，导致表面粗糙化增加。Rpit 说明了蚀刻坑发展的速度，观察到随着温度的增加而增加。基于 Rpit，相对较高的 Ea 值（121 kJ mol-1 和 162 kJ mol-1）与基底蚀刻坑的早期演化有关，而较低的值（36 kJ mol-1 和 56 kJ mol-1）与使用 Rbulk,Si 计算。本研究有助于解释在高酸性 pH 值、无机和有机酸存在以及低温 (T ≤ 80 °C) 下黑云母溶解过程所涉及的机制。此外，