Waste-porous-based materials as supports of TiO2 photocatalytic coatings for environmental applications

Abstract

Porous materials obtained through recycling glass-waste or volcanic materials such as foams and amorphous perlite granules could be used as excellent inorganic supports for catalytic coatings. These materials have good water absorption capacity that makes them good supports for catalytic and photocatalytic coatings with surface roughness. In addition to hygroscopic characteristics, their low density (approximately 0.41-0.44 g cm-3) allows floating on water (lightweight materials). These recycled materials present a chemical composition that is approximately 74% SiO2, 15% Al2O3, and 11% alkaline oxides and alkaline earth oxides that provide a negligible contribution for photocatalytic or catalytic applications. Perlite is an expanded material extensively used in aqueous photocatalytic degradations of dyes and organic contaminants and gas-phase degradation of VOCs like ethylene benzene coupled with biofilters, achieving degradation in 3 h. Waste-glass foams present activity for green tide annihilation and solar degradation of dyes using natural solar irradiation. Both systems present negligible lixiviation and good mechanical stability during photocatalytic performance. In the present work, coatings were obtained by several synthesis methods such as sonochemical deposition or acid impregnation process using nanocrystallinedoped sol-gel TiO2 or commercial TiO2. The physiochemical characterizations by HRTEM, XRD, UV-vis-DRS, and Raman or FTIR spectroscopies are discussed and correlated with environmental applications to obtain a better understanding of these novel ecomaterial systems. The practical active systems are a realistic strategy to scale up the systems to possible industrial applications and solve the emerging environmental pollution problems of industrialized cities.