| With the rapid development of dyeing and printing industry, the demand of dye increased massively, meanwhile, the emissions of dyeing wastewater increased massively. Dyeing wastewater, with the characteristics of dark color and low biodegradability, consumed the dissolved oxygen and reduced the sunlight transmission; the ecological balance of water environment was destroyed, which caused serious water pollution. Photocatalytic oxidation technology was an advanced oxidation technology, and the pollutant was degraded into CO2 and H2O by many active substances generated in photocatalytic process. Titanium dioxide (TiO2) was a photocatalyst with high stability, but there were serious problems when used in the photocatalysis technology, such as, solid-liquid separation and recycling of TiO2 were difficult. And these problems will be solved when TiO2 was loaded on activated carbon fibers. In this paper, Rhodamine B (RhB) and activated carbon fibers loaded with TiO2 (TiO2-ACF) was selected as the research object, the preparation method of TiO2-ACF and its characteristic were researched, and TiO2-ACF was used for the removal of aqueous RhB, meanwhile, main influence factors and the removal mechanism of Rhodamine B by ultraviolet light catalytic technology coupled with TiO2-ACF was studied.Firstly, TiO2-ACF composite materials were prepared by the sol-gel method. The structural features of the TiO2-ACF were investigated by XRD, SEM, UV-Vis, FT-IR, XPS and BET. The results showed that the TiO2 loaded on the activated carbon fiber was anatase, when the calcination temperatures were 400-600℃, and the phase transformation from anatase to rutile began at 700℃, TiO2 loaded on the activated carbon fiber calcined at 600 ℃ exhibited the best crystal form and crystallinity; Ti-O and TiO2-OH were formed at the surface of TiO2-ACF, TiO2-ACF prepared under different calcination conditions have almost the same of absorption spectral range, and the specific surface area of TiO2-ACF was less than that of ACF, but the mesoporous of TiO2-ACF increased.Secondly, adsorption of aqueous RhB with the TiO2-ACF was explored in this study. The results showed that the pseudo-second-order kinetic model and the Langmuir model were more suitable to describe the adsorption of RhB onto TiO2-ACF, meanwhile, the Freundlich isotherm was also suitable, monolayer adsorption and heterogeneous polymolecular layer adsorption were existed at the adsorption of RhB onto TiO2-ACF. The adsorption capacity of RhB onto TiO2-ACF increased significantly with the increase of temperature, which was an endothermic process. The pHPZC of TiO2-ACF was 4.07, and TiO2-ACF had a certain buffering capacity to the pH of solution, the removal rate of RhB was 85.68% under acid condition.Finally, efficient removal of RhB with ultraviolet light catalysis coupled with TiO2-ACF was explored in this study. The results showed that the adsorption ability of RhB onto TiO2-ACF was lower than that of ACF, but under the condition of UV irradiation, TiO2-ACF showed higher photocatalytic activity, the degradation rates of RhB were higher than those of ACF and TiO2 by 8.60% and 16.20%, respectively. And TiO2-ACF was a stable photocatalytic material.94.00% of RhB was degraded by TiO2-ACF calcined at 600℃. The removal rate of RhB increased with increasing UV lamp power, and decreased with increasing initial concentration and pH value. The removal rate of TOC was lower than that of RhB, and only partial RhB were mineralized. The amount of generated H2O2 increased gradually, pH decreased first then increased in the photocatalytic process, and the acute biological toxicity of RhB solution increased first then decreased, a small blue shift phenomenon of RhB sample was appeared. The degradation byproduct and the removal mechanism of RhB during the photocatalytic process were proposed according to the analysis of LC-MS and GC-MS, de-ethylation processes and hydroxylation were the main degradation way. |
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