ZnO Nanorods Grown on Flexible Polyurethane Foam Surfaces for Photocatalytic Azo Dye Treatment

A flexible photocatalyst hybrid structure made up of aligned ZnO nanorods and three-dimensional networks of polyurethane (PU) foam struts was fabricated. The surfaces of the PU struts were first functionalized by the two-step chemical solution treatment method. The functional groups of the PU foam and the nanohybrid structure were characterized using Fourier transmission infrared spectroscopy (FTIR). Their crystal structures and morphologies were examined by using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The adequacy of the chemical surface modification process was examined by analyzing the differences in the -N = C = O and O-H regions of the FTIR spectrum. The hybrid photocatalyst samples were also tested in terms of their structural integrities under ultrasonic irradiation. It was observed that the ZnO layers remained intact and adherent on the surfaces even after 1 h of sonication. The optical properties of the samples were also characterized by ultraviolet-visible (UV-vis) and photoluminescence (PL) spectroscopies. Aqueous Acid Red 88 (AR88) azo dye solutions were prepared and used to assess both the color and the total organic carbon (TOC) removal efficiencies of the samples utilizing the laboratory-scale photoreactor. The maximum color removal of 97% was reached in 180 min under UVA light irradiation as a consequence of simultaneous adsorption and photocatalysis mechanisms.