Efficiency of La-doped TiO2 calcined at different temperatures in photocatalytic degradation of β-blockers

Abstract

Photocatalytic activity of titania–based photocatalysts doped with 1% La has been tested in UVA radiation-induced degradation of two β-blockers – metoprolol tartrate (MET) and propranolol hydrochloride (PRO). Photocatalysts have been synthesized by sol–gel process followed by calcination at various temperatures in the range of 450–750°C. The great impact of calcination temperature on the structural, compositional and morphological properties of prepared catalysts has been revealed by XRPD, SEM, BET and Raman scattering measurements. Doped catalysts calcined at 450–650°C, with dominant anatase phase and developed mesoporous structure, have displayed higher photocatalytic performance than much less porous samples calcined at 700–750°C, with sodium hexatitanate as dominant phase. Also, La-doped anatase sample has shown higher efficiency in degradation of MET and PRO in comparison with the efficiency of undoped TiO2 nanopowders calcined at same temperatures. The quenching effects of various scavengers suggest that the major role in degradation of MET may be attributed to reactive radicals, whereas photogenerated holes are mainly responsible for degradation of PRO. Applying density functional theory (DFT) calculations, we analyzed fundamental structural and electronic properties (total and polar surface areas, frontier molecular orbitals, optoelectronic properties and average local ionization energy surfaces) of MET and PRO molecules, which are of significance for the understanding of more effective degradation of PRO in comparison with MET.