Titania-Coated Alumina Foam Photocatalyst for Memantine Degradation Derived by Replica Method and Sol-Gel Reaction

Abstract

In the present work, alumina (Al2O3) foam was prepared by the replica method where a polyurethane (PU) foam (30 pores per inch (ppi)) template was impregnated with a 60 wt.% Al2O3 suspension. Sintered Al2O3 foam was used as substrate for the deposition of sol-gel derived titania (TiO2) film using dip coating. For the preparation of TiO2 sol, titanium(IV) isopropoxide (Ti-iPrOH) was used as the precursor. The common problem of qualification and quantification of a crystalline coating on a highly porous 3D substrate with an uneven surface was addressed using a combination of different structural characterization methods. Using Powder X-ray Diffraction (PXRD) and synchrotron Grazing Incidence X-ray Diffraction (GIXRD) on bulk and powdered Al2O3 foam and TiO2-coated Al2O3 foam samples, it was determined Al2O3 foam crystallizes to corundum and coating to anatase, which was also confirmed by Fourier Transformed Infrared Spectroscopy (FTIR). Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM/EDS) revealed the structural and microstructural properties of the substrate and coating. Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) were used to clarify the evolution of the porous microstructure. The Al2O3-TiO2 composite was evaluated as a photocatalyst candidate for the degradation of the micropollutant medication memantine. The degradation rate was monitored using a light-emitting diode (LED) lamp operating at electromagnetic (EM) wavelength of 365 nm. The photocatalytic activity of sol-gel-derived TiO2 film immobilized on the Al2O3 foam was compared with commercially available TiO2 nanoparticles, P25-Degussa, in the form of a suspension. The levels of memantine were monitored by High-Performance Liquid Chromatography–Tandem Mass Spectrometry (HPLC–MS/MS). The efficiency and rate of the memantine photodegradation by suspended TiO2 nanoparticles is higher than the TiO2-coated Al2O3 foam. But, from the practical point of view, TiO2-coated Al2O3 foam is more appropriate as a valuable photocatalytic composite material.