Kaolin Waste Applied as Support for Photocatalytic Materials

Kaolin is a common mineral resource that is used commercially. However, when processed, it generates a large amount of waste, usually rich in kaolinite, mica and quartz, which gives rise to the need to manage and reuse these mineral residues, in agreement with the SDG 12/UN (ensuring sustainable consumption and production) requirements. Therefore, this work aims to explore how to add value to this residue via its use as a photocatalytic support for TiO 2 , while also meeting the SDG 6 (clean water and sanitization) requirements. After determination of its chemical and mineralogical composition, the residue underwent mineralogical separation, by mechanical stirring and sieving of its aqueous suspension. After separation, TiO 2 was deposited on the quartz fraction of the residue by the modified-Pechini method, using different quartz proportions and at different calcination temperatures. For the deposition of TiO 2 on the mica fraction, the conventional hydrothermal synthesis was used, with 20% of the mica. Each material was tested in a photohydroxilation of terephthalic acid under UV-C irradiation to evaluate the formation of hydroxyl radicals. The results of the photocatalytic tests demonstrated that quartz and mica are inert to photocatalysis but provide an interesting support for TiO 2 . The highest photocatalytic efficiency was obtained for the material synthesized at 600 °C with 20% of the quartz.