TiO2-loaded nanotubular kaolin group minerals: The effect of mineral support on photodegradation of dyes as model pollutants

Abstract

One prevailing trend in order to design efficient photocatalysts is to support TiO2 on kaolin-based mineral carriers. This prevents TiO2 aggregation, improves textural parameters and adsorption properties as well as lowers costs. This research is a comprehensive comparison of photocatalysts based on different TiO2-loaded kaolin group minerals, including platy kaolinite, halloysite, halloysite-containing sample, and raw and calcined synthetic kaolinite nanotubes. The impregnation of the platy kaolinite sample led to the formation of star-like TiO2 aggregates, which were unevenly attached to the platelets surface. In contrast, the TiO2 formed nanocrystallites that homogenously covered the external surface of synthetic calcined kaolinite nanotubes. These differences had a significant impact on the textural properties of the resulting photocatalysts. The sample based on calcined nanotubes achieved a specific surface area of 257.1 m2/g, which was ∼4.5 times higher than the photocatalyst based on raw kaolinite. These distinctions influenced the photocatalytic performance of the materials in the decomposition of dyes. The comparison of the results to the commercial photocatalyst P25 highlighted the high potential of selected materials in the photodegradation of methylene blue and safranin O. The practical applicability and sustainability of the investigated materials was also attested via successful experiments on their regeneration and reuse.