Titania-silica Composite with Photocatalytic Properties and Its Application on Brazilian Granite and Sandstone

ABSTRACT

The aim of the study described in this article was to evaluate a product containing titania (titanium dioxide, TiO₂) applied on stones — particularly two types used at Brazilian stone-built heritage sites — that have been exposed to weathering and anthropogenic activities. This product was prepared by producing a suspension of TiO₂ at two concentrations (1% and 4% w/v) with tetraethyl orthosilicate (TEOS) in the presence of n-octylamine as surfactant. The characteristics of the TiO₂ were then observed by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface-area measurements, particle-size distribution analysis (CILAS) and X-ray diffraction. After applying the TiO₂-TEOS composite, the stones were examined for contact angle, spectrophotometry, sorptivity, thermal shock resistance, and UV-radiation resistance. The product proved ineffective on Itararé sandstone, mainly due to its mineralogical components, as the product does not adhere to quartz. When applied on Itaquera granite, the 1% TiO₂ (w/v) concentration proved to be an appropriate treatment, as it demonstrated better thermal shock resistance, photocatalytic activity, porosity maintenance, and global colour when compared to the 4% concentration.

KEYWORDS:

• Architectural heritage
• Itaquera granite
• Itararé sandstone
• photocatalysis
• self-cleaning surfaces
• stone conservation
• Tio₂-Teos composite

Note from the Authors

This paper is dedicated to the memory of Prof. Valter Ussui who passed away on 21 January 2021. Graduated in Chemistry and PhD in Nuclear Technology, he dedicated most of his career at IPEN studying chemical processes for ceramic powder synthesis. Part of his contribution to the preservation of architectural heritage is presented in this paper where a titania-silica powders synthesis process was developed.

Acknowledgments

The authors acknowledge the comments and suggestions of the anonymous reviewers, which improved the manuscript.

The authors would like to thank Lucia Shibata for proof-reading the article and the members of the CCTM/IPEN Microscopy, XRD, and Cilas laboratories for the technical support they provided.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Comissão de Aperfeiçoamento de Pessoal de Nível Superior - CAPES (grant number 88882.315495/201901).