蒙脱石在不同 pH 值的草酸和硫酸介质中的溶解过程和机理

IF 5.3 2区 地球科学 Q2 CHEMISTRY, PHYSICAL
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引用次数: 0

摘要

硅酸盐矿物的溶解在许多自然地质过程中起着至关重要的作用。为了更好地理解蒙脱石在不同酸性体系中的反应机理和溶解特征,研究了蒙脱石与草酸和硫酸溶液在不同 pH 值下的界面反应对离子溶解、晶体结构和微观形态的影响,并模拟了铝的形态和次生矿物的饱和指数。结果表明,蒙脱石结构中 Mg2+、Al3+ 和 Si4+ 的溶出量随 pH 值的增加而减少,这反映了蒙脱石的溶出与溶液的 pH 值有关。蒙脱石与草酸溶液反应后,Mg2+、Al3+ 和 Si4+ 的溶出率均大于硫酸溶液,其中 Al3+ 的溶出率最高,说明配体和质子均攻击了蒙脱石的表面位点,加速了离子的溶出。此外,草酸盐配体对 Al3+ 离子具有特定的结合作用。在与草酸盐和硫酸盐反应时,蒙脱石的四面体阳离子、八面体阳离子和层间阳离子表现出不均匀和不一致的溶解。草酸盐配体对 Al3+ 有很强的络合作用,使草酸盐溶液中的 Al3+ 以草酸铝络合物的形式存在,从而降低了溶液中 Al3+ 的有效浓度,促进了蒙脱石结构中 Al3+ 的溶解。沉淀在八面体取代位点上的 Mg2+ 离子稳定性较弱,而来自层间的 Mg2+ 离子则具有较强的层间互换性,即使在 pH 值为 6.5 的草酸和硫酸溶液中,溶解度也分别高达 10.85 % 和 8.62 %。溶液中的所有次生矿物相均未饱和,使得蒙脱石的溶解难以平衡。蒙脱石具有很高的阳离子交换能力,因此对外源酸具有很强的缓冲能力。这项研究有助于解释蒙脱石在不同 pH 值的无机酸和有机酸溶液中的溶解过程。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Dissolution process and mechanism of montmorillonite in oxalic acid and sulfuric acid media at various pH levels

The dissolution of silicate minerals plays a crucial role in many natural geological processes. In order to better comprehend the reaction mechanisms and dissolution characteristics of montmorillonite in different acidic systems, the effects of interfacial reactions of montmorillonite with oxalic and sulfuric acid solutions at various pH levels on the ionic dissolution, crystal structure, and micro-morphology were studied, and the morphology of aluminum and saturation index of secondary mineral were simulated. It was shown that the dissolution amounts of Mg2+, Al3+ and Si4+ in montmorillonite structure decreased with the increase of pH value, which reflected the dependence of montmorillonite dissolution on the pH value of solution. The dissolution percentages of Mg2+, Al3+ and Si4+ after the reaction of montmorillonite with oxalic acid solution were greater than those in sulfuric acid solution, and the highest dissolution rate of Al3+, indicated that both ligands and protons attacked the surface sites of montmorillonite and accelerated the dissolution of ions. Moreover, oxalate ligands exerted specific binding effects on Al3+ ions. While reacting with oxalate and sulfate, the tetrahedral, octahedral and interlayer cations of montmorillonite exhibited the non-stoichiometric and inconsistent dissolution. The oxalate ligands have a strong complexation effect on Al3+, so that Al3+ in oxalate solution exists in the form of aluminum oxalate complex, which reduces the effective concentration of Al3+ in solution and promotes the dissolution of Al3+ in montmorillonite structure. The Mg2+ ions settled at octahedral substitution sites possessed weak stability, while those from the interlayer featured strong interlayer interchangeability, demonstrating the dissolution percentage up to 10.85 % and 8.62 % even in oxalic and sulfuric acid solutions at pH of 6.5. All secondary mineral phases in the solution were undersaturated, making the montmorillonite dissolution difficult to balance. Montmorillonite has a high cation exchange capacity, which makes it have a strong buffer capacity to exogenous acids. This study helps to explain the dissolution process of montmorillonite in inorganic and organic acid solutions at different pH value.

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来源期刊
Applied Clay Science
Applied Clay Science 地学-矿物学
CiteScore
10.30
自引率
10.70%
发文量
289
审稿时长
39 days
期刊介绍: Applied Clay Science aims to be an international journal attracting high quality scientific papers on clays and clay minerals, including research papers, reviews, and technical notes. The journal covers typical subjects of Fundamental and Applied Clay Science such as: • Synthesis and purification • Structural, crystallographic and mineralogical properties of clays and clay minerals • Thermal properties of clays and clay minerals • Physico-chemical properties including i) surface and interface properties; ii) thermodynamic properties; iii) mechanical properties • Interaction with water, with polar and apolar molecules • Colloidal properties and rheology • Adsorption, Intercalation, Ionic exchange • Genesis and deposits of clay minerals • Geology and geochemistry of clays • Modification of clays and clay minerals properties by thermal and physical treatments • Modification by chemical treatments with organic and inorganic molecules(organoclays, pillared clays) • Modification by biological microorganisms. etc...
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