Mesoporous Titania Nanoparticles Research Articles

Photocatalytic Degradation and Mineralization of Commercial Methamidophos in Aqueous Titania Suspension

The photocatalytic degradation of a commercial methamidophos (MAP) emulsion in aqueous suspension containing mesoporous titania (m-TiO2) nanoparticles under UV irradiation was investigated. The mineralization rate of MAP went up steadily as prolonging the irradiation time and reached ca. 95% after 4 h irradiation based on determination of the end-products (NO3-, PO4(3-), and SO4(2-)) of MAP through IC analysis. Moreover, the degradation kinetics of MAP followed the first-order reaction and has been monitored through GC-PFPD analysis, which also showed that MAP and the organic solvent as well as additive in the pesticide emulsion can be degraded readily and simultaneously. Photodegradation intermediates derived from two different concentrations of MAP were detected by GC-MS technique. The experimental facts indicated that the photodegradation mechanism of MAP mainly involves electron transfer process and hydroxylation process, and the dominant mechanism for MAP degradation in the initial steps can be attributed to the electron transfer process, which resulted in the formation of all intermediates containing P species detected in the initial photodegradation stage.

Photocatalytic degradation of methyl orange in aqueous suspension of mesoporous titania nanoparticles

The photodegradation of methyl orange (MO) was investigated in aqueous suspension containing titania nanoparticles with mesostructures (m-TiO 2) under UV irradiation. The experimental results show that 98% MO can be mineralized in the 1.0 g l −1 m-TiO 2 suspension (pH 2.0) after 45 min illumination. Particular attention was devoted to the identification and the transformation of the fragments retaining the chromophoric group. The photodegradation mechanism of the quinonoid MO mainly involves three intermedial processes: demethylation, methylation and hydroxylation. Among those processes, demethylation is more favorable than the hydroxylation, but the hydroxylation results in the largest number of intermediates. The degradation pathway of quinonoid MO under the optimal conditions is also proposed.

Preparation, phase transformation and photocatalytic activities of cerium-doped mesoporous titania nanoparticles

Cerium-doped mesoporous TiO 2 nanoparticles with high surface area and thermal stable anatase wall were synthesized via hydrothermal process in a cetyltrimethylammonium bromide (CTAB)/Ti(SO 4) 2/Ce(NO 3) 4/H 2O system. The obtained materials were characterized by XRD, FESEM, HRTEM, FTIR spectroscopy, nitrogen adsorption and DRS spectra. Experimental results indicated that the doping of cerium not only increased the surface area of mesoporous TiO 2 nanoparticles, but also inhibited the mesopores collapse and the anatase-to-rutile phase transformation. Moreover, the undoped, doped anatase mesoporous nanoparticles exhibit higher photocatalytic activity than commercial photocatalyst (Degussa, P25), but the maximum photodegradation rate corresponds to the undoped mesoporous TiO 2 nanoparticles. The lower photocatalytic activities of cerium-doped samples compared with undoped one may be ascribed to that the doped cerium partially blocks titania's surface sites available for the photodegradation and absorption of Rhodamine B (RB).

Synthesis of thermally stable mesoporous titania nanoparticles via amine surfactant-mediated templating method

Mesoporous titania nanoparticles with high specific surface area and thermal stable anatase wall was synthesized from surfactant laurylamine hydrochloride (LAHC) and inorganic precursor Ti(SO 4) 2. The as-synthesized and calcined materials were characterized by X-ray diffraction, nitrogen adsorption–desorption, transmission electron micrographs, Fourier transform infrared spectroscopy and thermogravimetric analysis. The obtained mesoporous TiO 2 nanoparticles have mean diameter of 25.5 nm. The specific surface area of the mesoporous nanosized TiO 2 calcined at 400 °C exceeded 189 m 2 g −1, and that of the samples after calcinations at 500 °C still have 151 m 2 g −1. The obtained anatase mesoporous TiO 2 nanoparticles show relative high thermal stability.