Zeolites are aluminosilicate minerals with multiple channels and cages. They are widely used in industry; further, owing to its increasing demand, the hydrothermal synthesis of zeolites from natural minerals/rocks has attracted great attention. This study aims to discuss the crystal growth mechanisms of zeolites from pumice. Pumice is a widely available porous volcanic glass (mainly consisting of 65–75% SiO 2 and 9–20% Al 2 O 3 ) that can be used in the fabrication of zeolites. In this study, zeolite was formed from pumice via a hydrothermal method with varying alkaline concentrations, reaction times and temperatures, and addition of NaCl. Zeolite Na-P1 was synthesized under conditions of 0.1 or 0.5 M at 150 °C. The feldspar phase (albite) initially occurred, followed by the zeolite phase (zeolite Na-P1). Phillipsite was an unstable intermediate product during this synthesis process. Based on these results, we suggest that the phase transformation sequence follows the order of albite, phillipsite, and zeolite Na-P1. Moreover, it can be speculated that an increase in cation concentration can induce a rapid occurrence of the zeolite phase (zeolite Na-P1). Raman spectrometry analyses provided insights into the formation mechanism of zeolite structures, indicating differences related to the number of sodium ions. Both zeolite Na-P1 and phillipsite are composed of four- and eight-membered rings, and the former is mainly grown with four-membered rings as the main structure. This study provides a low-cost and simple synthetic method for producing zeolite Na-P1 and phillipsite, which can be used as indicator minerals for marine/lake facies and in environmental treatment.

中文翻译：

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水热沸石合成的相变途径

沸石是具有多个通道和笼子的铝硅酸盐矿物。它们广泛应用于工业；此外，由于需求不断增加，从天然矿物/岩石中水热合成沸石已引起极大关注。本研究旨在探讨浮石沸石的晶体生长机制。浮石是一种广泛使用的多孔火山玻璃（主要由 65-75% SiO 2 和 9-20% Al 2 O 3 组成），可用于制造沸石。在这项研究中，沸石是通过水热法从浮石形成的，不同碱浓度、反应时间和温度，以及 NaCl 的添加。沸石 Na-P1 在 0.1 或 0.5 M 的条件下在 150 °C 下合成。最初出现长石相（钠长石），然后是沸石相（沸石 Na-P1）。在此合成过程中，Phillipsite 是不稳定的中间产物。基于这些结果，我们建议相变顺序遵循钠长石、菱镁矿和沸石 Na-P1 的顺序。此外，可以推测阳离子浓度的增加可以诱导沸石相（沸石Na-P1）的快速出现。拉曼光谱分析提供了对沸石结构形成机制的见解，表明与钠离子数量相关的差异。沸石Na-P1和phillipsite均由四元环和八元环组成，前者主要以四元环为主要结构生长。本研究为生产沸石 Na-P1 和 phillipsite 提供了一种低成本、简单的合成方法，