Immobilization Of Self-Assembly Of Pre-Dispersed Nano-TiO₂ On Surface Of Montmorrillonite And Its Photocatalytic Degradation On Organic Pollutant

Titanium dioxide (TiO2) is an important catalyst and catalyst support.TiO2 nanoparticles can be irritated by ultraviolet light at 390 nm or less to generate active oxygens such as hydroxyl radicals and superoxide anions. Active oxygens with a strong oxidizing activity can decompose organic materials and exhibit self-cleaning, deodorizing, and antibacterial effects.Nano-scaled TiO2 particles have large specific surface areas and are expected to have good catalytic activities since reactions take place on the TiO2 surface. However, when pure TiO2 powders are used, two main problems occur. First, ultrafine powder is easy to be agglomerated into larger particles, which results in negative effect on catalyst performance. Second, it is very hard to recover pure TiO2 powders from water when they are used in aqueous systems, which leads to a potential difficulty in downstream separation.A new immobilization way of nano-TiO2 on montmorillonite based on surfactant assembly was presented. In this paper there were two steps:First, an organic disperser was added into an aqueous solution of TiCl4 by hydrothermal method to prepare nano-TiO2 dispersed phase, and then assemblies of nano-TiO2 particles with assistant of surfactant were used to regulate the immobilization of nano-TiO2 particles on the interlayer surface of montmorrillonite to prepare TiO2-modified montmorillonite composites, which had higher photocatalytic performance. The results indicated that a good dispersed nano-TiO2 with size of 4.66nm was synthesized with the application of diethanolamine as disperser, and its interaction with cetyltrimethylammonium bromide (CTAB) to form assemblies of nano-TiO2 and CTAB which produced well-distributed nano-TiO2 modified montmorrillonite composites. The TiO2-modified montmorillonite composites prepared by assembly of pre-dispersed nano-TiO2 presented not only well-distributed TiO2 with ca.5.9nm on the interlayers of montmorillonite, but also distinct increase of specific surface area, average pore and volume which were beneficial to improve the adsorption capacities and photocatalytic performances of TiO2-modified montmorrillonite composites.Photocatalytic activity of these new materials were studied using 2,4-DCP solution as a reaction test. Experimental data fitted well to the Freundlich model at all temperatures studied. The kinetic experimental data were correlated with pseudo-second-order kinetic model. The adsorption rate was not controlled by film diffusion and particle diffusion. The activity of the decomposition processes were comparable and even superior to that of the commercial P25-anatase.