Impact of synthesis temperature on the physicochemical and optoelectronic properties of titania and oxidized carbon nanotube nanocomposites for the degradation of Remazol brilliant blue R

Abstract

A facile microwave irradiation-assisted hydrothermal method was employed in the synthesis of nanocomposites of titanium dioxide (TiO₂) and oxidized carbon nanotubes (OCNTs) to investigate the effect of synthesis temperature on their properties and photocatalytic performance. The synthesis temperatures used were 90, 120, 150, and 180 °C to produce nanocomposites T90, T120, T150, and T180, respectively. Attachment of TiO₂ to the surface of the OCNTs and presence of the OCNTs thereof was confirmed by transmission electron microscopy (TEM) as well as Raman spectroscopy. Powder X-ray diffraction (p-XRD) confirmed that the syntheses yielded the anatase titania crystalline polymorph. Ultraviolet (UV) spectroscopy results showed that the indirect energy bandgaps of the nanocomposites were all within the visible light range and increased with synthesis temperature in the order 2.34 eV, 2.75 eV, 2.87 eV, and 3.08 eV. Charge carrier recombination inhibition also increased with the synthesis temperature of the nanocomposites as revealed by the photoluminescence (PL) studies, at an excitation wavelength of 410 nm. The photocatalytic activities of the nanocomposites were tested in the photodegradation of Remazol brilliant blue R (RBBR) dye under sunlight for up to 180 min and the degradation followed the pseudo first order kinetics. Interestingly, the T180 nanocomposite demonstrated favorable comparability with other photocatalysts that have previously been applied for the degradation of RBBR dye in that, using sunlight , 99.1 % of the dye was degraded in a saline environment within 240 min, at a high pollutant to photocatalyst loading ratio. T180 further demonstrated high reusability without washing between the cycles by retaining in its 5th cycle 69.6 % and 89.5 % of its photocatalytic activity after 180 and 240 min, respectively. Based on this work, T180 is a potential catalyst for application in the remediation of industrial textile wastewater, especially laden with reactive dyes.