| Summary: | 碩士 === 大同大學 === 化學工程學系(所) === 103 === In this study, we used tetra-n-butyl titanate as precursor to synthesize TiO2 by hydrolysis method and fixed TiO2 on activated carbon. Materials were characterized by diffuse reflectance spectra (DRS), spectroscopic X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray microanalyses (SEM), scanning electron microscopy with energy dispersive X-ray microanalyses (SEM-EDX) and Brunauer-Emmett-Teller sorptometer (BET).
XRD spectra show that TiO2 with heat treatment at 105oC consists of anatase and brookite crystalline phases. SEM results show the particle size and morphology of materials, and TiO2 is well distributed on the surface of activated carbon, i.e., TiO2/AC.
The removal performance of AC and TiO2/AC was evaluated by UV-vis spectrophotometer to detect the concentration of methylene blue (MB). The removal efficiency of all materials increases with temperature increasing from 15oC to 45oC. TiO2/AC powder provides a high MB removal efficiency under UV light irradiation, up to 99% after 60 minutes.
From adsorption-desorption equilibrium experiments, the properties and the effects of TiO2 for adsorption process by kinetic models and isotherms are characterized. By fitting with kinetic models of 0th, 1st, 2nd reaction rate equation and Weber-Morris model, it can be found that (1) the processes of AC and TiO2/AC are better with 1st order reaction rate equation; (2) TiO2/AC had lower adsorption capacity at equilibrium that is due to part of activated sites being occupied by TiO2 particles; (3) intraparticle diffusion is not the sole rate-determining step in the reaction. By fitting with isotherms of Temkin, Freundlich and Langmuir, it can be found that (1) Langmuir isotherm model is the best fitted with the experimental data; (2) the adsorption process occurs on non-uniform surface; (3) the adsorption processes are principle in monolayer adsorption which is using functional groups of adsorbent surface as adsorption sites; (4) temperature increasing will be more favorable in adsorption; (5) the increasing maximum adsorption capacities (qmax) of the adsorbents at higher temperature is attributed to the enlargement of pore size.
|
|---|
