Characterization of selectively etched halloysite nanotubes by acid treatment

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Title: Characterization of selectively etched halloysite nanotubes by acid treatment
Authors: Garcia-Garcia, Daniel | Ferri, Jose M. | Ripoll-Seguer, Laura | Hidalgo, Montserrat | Lopez-Martinez, Juan | Balart, Rafael
Research Group/s: Espectroscopía Atómica-Masas y Química Analítica en Condiciones Extremas
Center, Department or Service: Universidad de Alicante. Departamento de Química Analítica, Nutrición y Bromatología | Universidad de Alicante. Instituto Universitario de Materiales
Keywords: Halloysite nanotubes | Lumen enlargement | Acid treatment | Catalysis | LIBS
Knowledge Area: Química Analítica
Issue Date: 15-Nov-2017
Publisher: Elsevier
Citation: Applied Surface Science. 2017, 422: 616-625. doi:10.1016/j.apsusc.2017.06.104
Abstract: Halloysite nanotubes (HNTs) are a type of naturally occurring inorganic nanotubes that are characterized by a different composition between their external and internal walls. The internal walls are mainly composed of alumina whilst external walls are composed of silica. This particular structure offers a dual surface chemistry that allows different selective surface treatments which can be focused on increasing the lumen, increasing porosity, etc. In this work, HNTs were chemically treated with different acids (sulphuric, acetic and acrylic acid), for 72 h at a constant temperature of 50 °C. As per the obtained results, the treatment with sulphuric acid is highly aggressive and the particular shape of HNTs is almost lost, with a remarkable increase in porosity. The BET surface area increases from 52.9 (untreated HNTs) up to 132.4 m2 g−1 with sulphuric acid treatment, thus showing an interesting potential in the field of catalysis. On the other hand, the treatment with acetic acid led to milder effects with a noticeable increase in the lumen diameter that changed from 13.8 nm (untreated HNTs) up to 18.4 nm which the subsequent increase in the loading capacity by 77.8%. The aluminium content was measured by X-ray fluorescence (XRF) and laser induced breakdown spectroscopy (LIBS). The final results using two systems, suggest a good correlation between the acid strength and the aluminium reduction. Consequently, is possible to conclude that new applications for HNTs can be derived from selective etching with acids. Sulphuric acid widens the potential of HNTs in the field of catalysis while weak acids such as acetic and acrylic acids give a controlled and homogeneous lumen increase with the corresponding increase in the loading capacity.
Sponsor: This work was supported by the Ministry of Economy and Competitiveness − MINECO [MAT2014-59242-C2-1-R]. D. Garcia-Garcia wants to thanks the Spanish Ministry of Education, Culture and Sports for their financial support through an FPU grant [FPU13/06011].
ISSN: 0169-4332 (Print) | 1873-5584 (Online)
DOI: 10.1016/j.apsusc.2017.06.104
Language: eng
Type: info:eu-repo/semantics/article
Rights: © 2017 Elsevier B.V.
Peer Review: si
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