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Open AccessArticle

Obsidian as a Raw Material for Eco-Friendly Synthesis of Magnetic Zeolites

1
Istituto di Metodologie per l’Analisi Ambientale—CNR, 85050 Tito Scalo, Italy
2
Departments of Chemistry and Industrial Chemistry (DCIC), Università of Genova, 16146 Genova, Italy
3
Istituto di Struttura della Materia—CNR, 00015 Monterotondo Scalo, Italy
4
Dipartimento di Scienze, Università degli Studi Roma Tre, 00146 Roma, Italy
*
Author to whom correspondence should be addressed.
Materials 2020, 13(20), 4633; https://doi.org/10.3390/ma13204633
Received: 11 September 2020 / Revised: 13 October 2020 / Accepted: 15 October 2020 / Published: 16 October 2020
(This article belongs to the Special Issue Green and Eco-Friendly Nanotechnology)
A sample of rhyolitic obsidian (OS) was used as raw material for zeolite synthesis by long (4 days) and fast (2 h)-aging hydrothermal processes. Zeolite synthesis was also performed by a fast (2 h) sonication method. The products were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) both immediately after and 3 years after their formation in order to determine the stability of synthetic materials according to the method used. The results confirm zeolitization of obsidian both by long-aging conventional hydrothermal heating and fast hydrothermal process. However, the data highlight the efficiency of direct ultrasound energy in achieving more stable zeolite crystals over time. These results carried out using a natural source, follow those already obtained using wastes and pure sources as raw materials thus providing a definitive validation of the different mechanisms controlling zeolite formation according to the process used. Moreover, the results confirm the effectiveness of ultrasonic energy in the formation of zeolites that are more stable over time. Due to the chemical composition of the obsidian precursor, all synthetic zeolites show good magnetic properties (i.e., saturation magnetization), in view to potential magnetic separation. View Full-Text
Keywords: obsidian; ultrasonic and hydrothermal water bath; zeolite; magnetic properties obsidian; ultrasonic and hydrothermal water bath; zeolite; magnetic properties
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Belviso, C.; Peddis, D.; Varvaro, G.; Abdolrahimi, M.; Reverberi, A.P.; Cavalcante, F. Obsidian as a Raw Material for Eco-Friendly Synthesis of Magnetic Zeolites. Materials 2020, 13, 4633.

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