Visible - Light Photocatalytic Degradation Performance Of Different Nano - TiO 2 Supported Fabrics And Their Applications

In order to apply nano-TiO₂materials to textile processing better, two nano-TiO₂hydrosols （denoted as TiO2-S-1 and TiO2-S-2） were synthesized at room temperature and two commercial nano-TiO₂powders （5 nm and 30 nm） were dispersed in water （denoted as TiO2-P-5 and TiO2-P-25） to prepare four different nano-TiO₂loaded cotton fabrics using pad-dry process, respectively. On the basis of characterization by using field emission electron microscopy, X-ray diffraction, UV visible diffuse reflectance spectra and energy spectra, four different nano-TiO₂loaded cotton fabrics were used as photocatalysts for the degradation of the organic dyes with different structures in the water. Some factors affecting their catalytic degradation of the dye such as the nano-TiO₂nature, irradiation intensity, pH value, dye molecule structures and concentrations, inorganic salts and surfactant were researched systematically, and the differences of combination modes between nano TiO₂particles and fibers and photocatalytic degradation characteristics of four different nano-TiO₂particles were emphatically studied. The degradations of different structure dyes catalyzed by TiO2-S-1 were carried out under the condition of sunny and cloudy days to evaluate the solar radiation usability of nano-TiO₂materials. The quantitative relationship between solar radiation intensity and catalytic performance were studied, as well as the effects of dyes structures and concentrations, and solution pH values. Nano-TiO₂hydrosols were modified with iron ions, triethylamine, and graphene, respecitvely, and the improvement of catalysis of nano-TiO₂loaded cotton fabrics were studied by photocatalyzing degrading formaldehyde in indoor air.The results indicated that four nano-TiO₂were characterized to be anatase type, and their particles sizes were between 1.5 nm and 2.5 nm, which smaller than the other two commercial nano-TiO₂powders. Four nano-TiO₂loaded cotton fabrics could be prepared through pad-dry-cure process, and three small sizes nano-TiO₂particles on the surface of cotton fabrics showed the similar morphology, which was significantly different from that of TiO2-P-5 formed on the surface of cotton fabric. Most importantly, the synthesized nano-TiO₂hydrosols had better light adsorption nano-TiO₂powders. All these four types of nano-TiO₂loaded cotton fabrics can significantly promote the photocatalytic degradation of azo dyes and anthraquinone dyes, and TiO2-S-1、TiO2-S-2 and TiO2-P-5 loaded cotton fabrics have higher catalytic activity in acidic and neutral solution under the irradiation of visible light. Inorganic salt NaCl, anionic surfactant （sodium dodecyl benzene sulfonic acid） and nonionic surfactant （alkyl phenol polyoxyethylene ether） have different inhibitory effects on the photocatalytic activity of these four types of nano-TiO₂loaded cotton fabrics, but the powder type nano-TiO₂show better tolerance than the hydrosol type nano-TiO2. The photocatalytic degradation reaction of the dye follows the pseudo first order kinetic reaction model in the presence of the nano-TiO₂loaded cotton fabrics. Nano-TiO₂loaded cotton fabric can still cause degradation reaction of azo dye under sunlight irradiation, and The catalytic activity of nano-TiO₂loaded cotton fabric was improved significantly by increasing its nano-TiO₂content. In particular, there is a positive linear correlation between its catalytic activity and the intensity of solar radiation. At the same time, the photocatalytic degradation of dyes under varying solar radiation intensities still follows the pseudo first order kinetic reaction model. Appropriately increasing the concentrations of NaCl and anionic surfactant resulted in a more inhibition effect for the catalytic activity of nano-TiO₂loaded cotton fabric, but this inhibition effect is much lower in the sunny days than that in cloudy days. Nano-TiO₂loaded cotton fabrics also could photocatalytically degrade the formaldehyde in indoor air. Increasing loaded content of nano-TiO₂and introduction of ultraviolet radiation would significantly improve the photocatalytic degradation of formaldehyde in the air, as well as the introduction of iron ion by modified reaction for nano-TiO₂hydrosols. The addition of a fixing agent can firmly attach nano-TiO₂particles to the surface of the cotton fabric, resulting in a lasting photocatalytic degradation effect.