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首页> 外文期刊>American Journal of Science >EXPERIMENTAL DISSOLUTION OF SANIDINE UNDER HYDROTHERMAL CONDITIONS: MECHANISM AND RATE
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EXPERIMENTAL DISSOLUTION OF SANIDINE UNDER HYDROTHERMAL CONDITIONS: MECHANISM AND RATE

机译:水热条件下桑定碱的实验溶解:机理和速率

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Dissolution rate measurements of sanidine at 100° to 300℃ provide new insight into the rate limiting reactions governing feldspar dissolution behavior close to chemical equilibrium. The experiments were conducted under various conditions, but mainly at neutral pH and at saturation with respect to quartz, these conditions being assumed to be representative of diagenetic and hydrothermal environments. Far from equilibrium, the activity of aqueous silica is found to control the rate at near neutral pH. Our results, when compared to other published studies, suggest a competition between two parallel reactions at the mineral surface: the hydrolysis of the Si and Al network-former oxides. In closed system experiments, the precipitation of secondary minerals such as clays is not observed; we found evidence only for the development of a thick potassium-leached layer at 300℃. The solution composition suggests that a thermodynamic "equilibrium" is essentially attained (constant composition with time) but not with respect to the bulk sanidine, at least at 100℃. By combining solution and surface analyses, we propose that local equilibrium at the reactive sites explains this apparent metastable equilibrium.
机译:在100°至300℃下测定山南定的溶出速率,为控制长石溶解行为接近化学平衡的限速反应提供了新的见解。实验是在各种条件下进行的,但主要在中性pH和相对于石英饱和的条件下进行,这些条件被认为是成岩和热液环境的代表。发现二氧化硅水溶液的活性远未达到平衡,在接近中性pH值时控制了其速率。与其他已发表的研究相比,我们的结果表明,在矿物表面发生的两个平行反应之间存在竞争:Si和Al形成网络的氧化物的水解。在封闭系统实验中,未观察到次生矿物质如粘土的沉淀。我们发现证据仅表明在300℃时钾浸出层较厚。溶液组成表明,至少在100℃时,基本上达到了热力学“平衡”(随时间恒定的组成),但相对于本体的山idine碱则没有。通过结合溶液和表面分析,我们建议反应部位的局部平衡可以解释这种明显的亚稳态平衡。

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