Abstract
Mesoporous nanotitania photocatalysts were prepared by sol-gel method in acidic or basic media. Three types of surfactants, namely, cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, and nonylphenol ethoxylate, were used as templating agents. The effects of surfactant type and pH on the morphology, particle size, surface area, pore-size distribution, UV-Vis absorbance, and TiO2phase transformation were traced by SEM, TEM, BET, and XRD. In absence of surfactants, XRD revealed 54.5% anatase at pH 3-4 and 97.0% at pH 7–9. In presence of surfactant, phase transformation of anatase has been significantly inhibited such that anatase amounts to 82–100% in acidic media. In basic media, the brookite phase appeared in low concentrations (8–15%) while rutile totally disappeared. The photocatalytic performance of the synthesized catalysts was tested via naphthalene degradation, which exhibited high activity in visible irradiation (>400 nm). The data obtained indicate that the surface area and pore volume of the current catalysts are the most effective factors for photocatalytic performance. Nevertheless, at the low pH (acidic) range, the CTAB templated catalyst gave the highest surface area (86.7 cm3/g), which is mainly assigned to acquiring the highest photocatalytic degradation of naphthalene (97% after 4 h irradiation time).
Highlights
The properties of nanocrystals depend on their chemical compositions, and on their structures, phases, shapes, sizes, and dimensionality [1]
In order to prevent the growth of nano-TiO2, the influence of the surfactant types on the particle size distribution of TiO2, including anionic surfactant DBS, cationic surfactant cetyltrimetylammonium bromide (CTAB), and nonionic surfactant nonylphenol ethoxylate (NPE), is studied
The intensity of Ti–O bonds is weakened and the system becomes easier to hydrolyze with higher speed of TiO2 nucleation
Summary
The properties of nanocrystals depend on their chemical compositions, and on their structures, phases, shapes, sizes, and dimensionality [1]. An interesting method to fabricate highly porous materials with desired pore structure and size for target specific applications is the use of amphiphilic organic molecules such as surfactants and block copolymers as pore directing agents in sol-gel methods [8]. Naphthalene (NP C10H8) is a polycyclic aromatic hydrocarbon (PAH), which is a widespread environmental contaminant because of its generation as a combustion byproduct and use as a pesticide and pesticide synthesis intermediate and as component of fuels such as JP-8 [12] Since it is the most water-soluble PAH (solubility 25–30 mg L−1 at ambient temperature), it is the dominant one in water. In this work, we modified the sol-gel method through using three types of surfactants (cationic, anionic, or nonionic) in acidic or basic media for controlling the phase structure, size, crystallinity, mesoporosity, and the light absorptivity in the visible range. The photocatalytic activity of the nanostructured mesoporous TiO2 catalyst has been tested in photodegradation of naphthalene as a water pollutant model compound
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