Effect of calcination temperature on the catalytic activity of nanosized TiO2 for ozonation of trace 4-chloronitrobenzene

Abstract

Nanosized titanium dioxides were synthesized by hydrolysis of TiCl(4) followed by calcination at different temperatures ranging from 300 to 1,000 °C. The as-prepared samples were characterized by X-ray diffraction, N(2) adsorption-desorption, and zeta potential analysis. The catalytic activities of the TiO(2) nanoparticles were tested by catalytic ozonation of trace 4-chloronitrobenzene (4-CNB) in water. Moreover, the catalytic ozonation activity of a sample calcined at 400 °C (denoted as T400) was tested in aqueous solution using electron paramagnetic resonance (EPR) spin trapping technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin trap. It was found that with increasing calcination temperatures, the average crystallite size and average pore size increased, in contrast the BET surface areas decreased. However, the isoelectric point (IEP) first increased, and then decreased. The ozone adsorption on the catalyst surface played an important role in determining their catalytic activity. Sample T400 with the IEP of 7.0, farthest away from the 4-CNB solution pH value (pH = 5.3), showed the best catalytic activity. The EPR experiments further confirmed that the hydroxyl radicals TiO(2)-catalyzed ozonation followed a radical-type mechanism.

The Adsorption of Ozone on the Solid Catalyst Surface and the Catalytic Reaction Mechanism for Organic Components

“…In 2007 and 2012, two research groups, Hernandez‐Alonso's group [12f] and Ye's group, [12g] used EPR to confirm that eq. (6) occurred during the adsorption of ozone on the TiO 2 surface to form an ozone anion, and the EPR signal was located at 2.003−2.009.…”

“…The main differences of ozonation reaction with the free radical mechanism come from producing free radicals. There were four kinds of ozone adsorption‐decomposition sites and methods reported in the literature: In the first type, after adsorption on the strong Lewis acid sites, ozone molecules decomposed and produced atomic oxygen, hydroxyl radicals, and other oxygen species [11,12f–l] . In the second type, ozone molecules were adsorbed by hydroxyl groups or adsorbed water molecules on the catalyst surface and then decomposed into hydroxyl radicals [12o,13a,c,d,30] .…”

Application of Heterogeneous Catalytic Ozonation for Refractory Organics in Wastewater

“…Iron oxide catalysts have been widely used in wastewater treatment (Table 5), like dyes [68], phenol [69], p-chlorobenzoic acid [70], nitrobenzene [71], and the tertiary treatment of industrial wastewater [72]. They have received increasing attention due to their advantages, such as (1) abundance;…”

“…They also proposed the reaction mechanisms for O 3 /CFO NPs catalytic ozonation (Equations (40)-(49)). 68.3% of TOC was removed within 120 min. The results showed that these spinel ferrites owned the reducibility and the electron donating capacity.…”

One-pot green synthesis of cerium oxide–carbon microspheres and their catalytic ozonation activity

“…4 Various types of heterogeneous catalysts including Fe 2 O 3 , MnO 2 , TiO 2 , Al 2 O 3 , activated carbon (AC) have been investigated in catalytic ozonation. [5][6][7][8][9][10] Metal oxides seem to play a major role in the generation of _OH. 11 These oxides represent one of the most important classes of solid catalysts.…”