Photocatalytic degradation of pharmaceuticals using natural sand-based TiO2 catalysts: Preparation, characterization, and reactivity

Abstract

Quartz sand collected from the dunes of Taghit, a region of Bechar in southwestern Algeria, served a dual purpose in this study. Firstly, it acted as a natural support for the TiO₂ photocatalyst. Secondly, it served as a low-cost precursor for silica extraction through an alkaline fusion process. TiO₂ nanoparticles were efficiently immobilized on both Dune Sand (TiO₂-DS) and extracted silica (TiO₂-SP) using an organometallic coating approach, providing a versatile TiO₂-based photocatalyst solution. Characterizing the prepared catalysts included techniques such as ICP, N₂ adsorption XRD, FTIR, FESEM, and XPS. It was noted that TiO₂ exhibited a well-coated layer on both dune sand and extracted silica, demonstrating a prominent anatase crystalline phase. Chemical composition analysis revealed the presence of chemical bonds between Ti and Si in the TiO₂-SP and TiO₂-DS samples. Moreover, TiO₂ particles showed improved dispersion on the surface of TiO₂-SP compared to TiO₂-DS due to the larger specific surface area of the extracted silica resulting in S_BET of 83.74 m².g⁻¹ for TiO₂-SP compared to 30.15 m².g⁻¹ for TiO₂-DS. The photocatalytic performance of TiO₂-DS and TiO₂-SP was compared to P25 in the abatement of three common pharmaceutical compounds: amoxicillin (AMO), ibuprofen (IBU), and acetaminophen (ACT), with a focus on the influence of the support material on photoactivity. TiO₂-SP exhibited a slight advantage in terms of mineralization with 90 %, 92 %, and 99 % after 300 min for ACT, AMO, and IBU, respectively, Whereas the TiO₂-DS catalyst resulted in slightly lower results of 81 %, 85 %, and 97 % for the same drugs over the same irradiation period. Additionally, both TiO₂-SP and TiO₂-DS demonstrated easy separation from the reaction medium by quick sedimentation upon agitation cessation. In contrast, P25 remained in a colloidal suspension.