Ultrasonic-assisted sol-gel method of preparation of TiO2 nano-particles: Characterization, properties and 4-chlorophenol removal application

Abstract

Nano-size TiO2 photocatalysts were prepared by sol-gel and ultrasonic-assisted sol-gel methods using two different sources of ultrasonicator, i.e., a bath type and tip type. The physicochemical characteristics of the catalysts were investigated by BET, XRD and TEM analyses and the photocatalytic properties of the TiO2 catalysts prepared by three different methods were compared. The intrinsic and extrinsic properties of TiO2, such as the particle size, surface area, pore-volume, pore-diameter, crystallinity as well as anatase, rutile and brookite phase ratios, could be controlled by the ultrasonic-assisted sol-gel method. During this preparation method, the effect of such important operating variables as the ultrasonic irradiation time, power density, the ultrasonic sources (bath-type and tip-type), magnetic stirring during synthesis, initial temperatures and size of the reactors are discussed here. It was found that each of the parameters played a significant role in controlling the properties of the TiO2 nano-particles. Among the three different methods, TiO2 photocatalysts prepared by ultrasonic (tip-US) assisted sol-gel possessed the smallest particle size, highest surface area and highest pore-volume than the catalysts prepared by the other two methods. 4-Chlorophenol was used as a pollutant to observe the photocatalytic degradation ability of the prepared photocatalysts and the TiO2 catalysts prepared by the bath-US ultrasonic-assisted sol-gel method were shown to be the most highly active. This is due to their high surface area and high pore-diameter. This study clearly demonstrates the importance and advantages of ultrasonication in the modification and improvement of the photocatalytic properties of mesoporous nano-size TiO2 particles.

Ultrasonic enhancement of the acidity, surface area and free fatty acids esterification catalytic activity of sulphated ZrO 2 –TiO 2 systems

“…It is reported in the literature that the addition of TiO 2 to ZrO 2 can increase the surface concentration of -OH groups [27,28]. This behaviour is generally observed for mixed oxides and it is probably due to the charge imbalance resulting from the heteroatoms linkage for the generation of acid centres [29].…”

Combined SANS and SAXS study of the action of ultrasound on the structure of amorphous zirconia gels

“…The advantages of the ultrasound-assisted sol-gel technique over conventional routes of nanomaterials synthesis include shortening the synthesis duration due to faster hydrolysis, leading to more uniform particle size distribution, higher surface area, better thermal stability, and improved phase purity [4]. Examples of successful ultrasound-assisted sol-gel synthesis of metal oxide nanostructures include TiO 2 [8][9][10], ZnO [11][12][13], MoO 3 [14], In 2 O 3 [15], ZrO 2 [16], SiO 2 [17][18][19], etc. It was shown that in a number of cases, sonochemically prepared materials demonstrate better characteristics than those synthesized by conventional methods.…”

Designing Nanostructured Carbon Xerogels

“…However, although no solvent exchange or high operating pressures are involved, it is still a long drying procedure (about 34 hours). There are many works about polymerization reactions and other types of chemical processes that are accelerated by ultrasonic radiation (Neppolian et al, 2008;Riera et al, 2010;Suslick et al, 1999;Tonamon et al, 2005). Several authors have employed ultrasonic radiation in one or several steps to synthesize carbon gel.…”