Dipartimento di Ingegneria e Geologia, Università Degli Studi "G.D'Annunzio", Via dei Vestini 30, 66013, Chieti, Italy.
Dept. Mineralogia, Petrologia I Geologia Aplicada, Universitat de Barcelona, 08028, Barcelona, Spain.
Sci Rep. 2021 Jun 28;11(1):13373. doi: 10.1038/s41598-021-92862-0.
Analcime is nowadays an important component in dental porcelain systems, in heterogeneous catalysis, in the nanoelectronic field, in selective adsorption and in stomatology (dental filling and prosthesis). Analcime synthesis from an impure, silica-rich kaolinite rock coming from Romana (Sassari, Italy) is here presented. A synthesis protocol is proposed that aims to make an improvement of synthesis conditions compared to the past. The hydrothermal treatment is in fact here achieved without aging times and without the use of sodium silicate or other additional silica source reported in the literature. Lower calcination temperature, synthesis temperature and crystallization time are verified in this work. The kaolin is subjected to calcination at the temperature of 650 °C and then mixed with NaOH. The experiment is performed at ambient pressure and 170 ± 0.1 °C. The degree of purity of analcime is calculated in 97.57% at 10 h. Analcime is characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, inductively coupled plasma optical emission spectrometry and thermal analysis. Density is also calculated. Cell parameters and the amount of amorphous phase in the synthesis powders is estimated with quantitative phase analysis using the combined Rietveld and reference intensity ratio methods. The experimental conditions make the synthesis protocol particularly attractive from an economic point of view. Also this work does not use a commercial kaolin but silica-rich impure kaolinitic rock from a disused quarry. This further reduces the costs of the experimental protocol. It also gives the protocol an added value, as the synthesis of a useful mineral is obtained through the valorization of an otherwise unused georesource. Both chemical and physical characterization of analcime is satisfactory making the experimental protocol very promising for an industrial transfer.
方沸石如今是牙科瓷体制备、多相催化、纳米电子学、选择性吸附和口腔医学（牙齿填充和修复体）等领域的重要组成部分。本文介绍了从来自意大利撒丁岛罗马纳（Romana）的不纯富硅高岭石岩中合成方沸石的方法。提出了一种旨在改进过去合成条件的方案。水热法实际上是在没有陈化时间的情况下进行的，也没有使用文献中报道的硅酸钠或其他额外的硅源。在这项工作中验证了较低的煅烧温度、合成温度和结晶时间。高岭土在 650°C 下煅烧，然后与 NaOH 混合。实验在环境压力和 170±0.1°C 下进行。方沸石的纯度计算值为 97.57%，反应时间为 10 小时。对方沸石进行了 X 射线衍射、红外光谱、扫描电子显微镜、电感耦合等离子体发射光谱和热分析。还计算了密度。使用结合 Rietveld 和参考强度比方法的定量相分析对方沸石合成粉末的晶胞参数和非晶相含量进行了估计。实验条件使得该合成方案从经济角度来看极具吸引力。此外，该工作没有使用商业高岭土，而是使用来自废弃采石场的富硅不纯高岭石岩。这进一步降低了实验方案的成本。它还为该方案增加了附加值，因为通过利用原本未被利用的地质资源来合成有用的矿物。方沸石的化学和物理特性都令人满意，这使得该实验方案非常有希望进行工业转移。
