Hydrophobic TiO2 -SiO2 Aerogel Composites for Fast Removal of Organic Pollutants

Ag-Incorporated Cr-Doped BaTiO3 Aerogel toward Enhanced Photocatalytic Degradation of Methyl Orange

A novel Cr-doped BaTiO3 aerogel was successfully synthesized using a co-gelation technique that involves two metallic alkoxides and a supercritical drying method. This freshly prepared aerogel has a high specific surface area of over 100 m2/g and exhibits improved responsiveness to the simulated sunlight spectrum. Methyl orange (MO) was chosen as the simulated pollutant, and the results reveal that the Cr-doped BaTiO3 aerogel, when modified with the noble metal silver (Ag), achieves a pollutant removal rate approximately 3.2 times higher than that of the commercially available P25, reaching up to 92% within 60 min. The excellent photocatalytic performance of the Ag-modified Cr-doped BaTiO3 aerogel can be primarily attributed to its extensive specific surface area and three-dimensional porous architecture. Furthermore, the incorporation of Ag nanoparticles effectively suppresses the recombination of photo-generated electrons and holes. Stability and reusability tests have confirmed the reliability of the Ag-modified Cr-doped BaTiO3 aerogel. Therefore, this material emerges as a highly promising candidate for the treatment of textile wastewater.

An overview on alumina-silica-based aerogels

Silica aerogels are remarkable materials with excellent physicochemical properties, such as high porosity and surface area, along with low density and thermal conductivity. In addition to their outstanding properties, these materials are quite interesting due to the possibility to change their chemistry according to intended applications. However, they also show some disadvantages, like low mechanical strength and poor dimensional stability under high temperatures (above 600 °C). Although these aerogels are frequently used as thermal insulators, for high temperature environments some of their properties need to be improved. The mixing with other ceramic thermally resistant phases is a viable approach. Thus, this work presents an overview on alumina-silica-based aerogels, describing their synthesis, processing and properties. The improvement on their properties will be discussed as a function of the amount of refractory phase (alumina) in the silica matrix. The introduction of the alumina phase makes them stable until 1200-1400 °C, maintaining low values of thermal conductivity at very high temperature (below 81 mW m^-1 K^-1). Finally, a brief survey on the most promising applications of these materials is presented, with several examples. In catalysis, alumina-silica aerogels have shown equivalent performance when compared to reference catalysts. In the field of thermal insulation, these materials show great potential, especially in high temperatures environments, due to their thermal dimensional stability and inherent low thermal conductivity. As adsorbents, higher stability and adsorption capacity were obtained with the incorporation of the alumina phase in silica aerogels, and these materials can be reused for repeated adsorption/desorption cycles. Indeed, a significant improvement of the aerogel performance by the synergetic effect of combining silica and alumina phases is usually obtained, supporting the expectation of the extension of their fields of application.