Photocatalytic Oxidation of Urea on Surface-Modified Bi 2 WO 6 with trans -4-Stilbenecarboxaldehyde

Abstract

Modification of the Bi2WO6 surface with trans-4-stilbenecarboxaldehyde (4SCA) by the equilibrium adsorption method and its application in photoredox reactions under solar irradiation were studied. The modification of the surface of Bi2WO6 at acidic pH implied an acetal-type interaction with the aldehyde, and then the separation of the solid at neutral pH guaranteed the irreversible covalent functionalization. Langmuir isotherm measurements and infrared spectroscopy support the surface modification. Studies based on stationary and time-resolved photoluminescence spectroscopy showed the effect on the dynamics (lifetime) of charge carrier deactivation due to surface modification. A higher rate of formation of the hydroxyl radical using Bi2WO6-4SCA as compared to Bi2WO6 was measured. The photocatalytic tests carried out in a tubular bench reactor (TBR) showed improvements of the modified Bi2WO6 in the mineralization of urea. In addition, the latter process became faster as the initial urea concentration was decreased. Langmuir-Hinshelwood kinetic parameters for urea oxidation were measured and discussed. These findings are important to understand the deactivation dynamics of excited electrons at the semiconductor-electrolyte interphase and to optimize the conditions necessary to carry out an efficient photoredox reaction (e.g., degradation of an important pollutant such as urea).