Surface Modification of TiO₂ Nanoparticles For Photochemical Reduction of Nitrobenzene

Abstract

The effects of surface modification of nanocrystalline titanium dioxide (TiO 2 ) with specific chelating agents on photocatalytic degradation of nitrobenzene (NB) was investigated in order to design a selective and effective catalyst for removal of nitroaromatic compounds from contaminated waste streams. Mechanisms of NB adsorption and photodecomposition were investigated using infrared absorption and electron paramagnetic resonance spectroscopy. Liquid chromatography and gas chromatography/mass spectrometry were used for byproduct analyses. Arginine, lauryl sulfate, and salicylic acid were found to bind to TiO 2 via their oxygen-containing functional groups. Modification of the TiO 2 surface with arginine resulted in enhanced NB adsorption and photodecomposition, and compared to unmodified TiO 2 . The initial quantum yield for photodegradation of NB in this system was found to be Φ init ) 0.31 as compared to the one obtained for Degussa P25 of Φ init ) 0.18. NB degradation followed a reductive pathway over arginine-modified TiO 2 and was enhanced upon addition of methanol. No degradation of arginine was detected under the experimental conditions. Arginine improved the coupling between NB and TiO 2 and facilitated the transfer of photogenerated electrons from the TiO 2 conduction band to the adsorbed NB. These results indicate that surface modification of nanocrystalline TiO 2 with electron-donating chelating agents is an effective route to enhance photodecomposition of nitroaromatic compounds.

Wet air oxidation of nitrobenzene enhanced by phenol

“…Since the degradation of nitrobenzene is very difficult to achieve, severe conditions were needed for its oxidation such as supercritical water oxidation (Arslan-Alaton and Ferry, 2002;Zhang and Hua, 2003). Other advanced oxidation processes like photocatalytic oxidation (Makarova et al, 2000;Rodriguez et al, 2002), sonolysis/ozonolysis (Weavers et al, 1998), ozonation and O 3 /UV processes (Contreras et al, 2001), Fenton oxidation have been investigated for the same purpose. However, these methods are either expensive or ineffective for the treatment of nitrobenzene-containing wastewaters.…”

Photocatalytic degradation pathways and adsorption modes of H-acid in TiO2 suspensions

“…Thus, to investigate the role of sulfonic groups in the adsorption of H-acid on TiO 2 surfaces, the adsorption of H-acid on TiO 2 covered with PFOS was also studied. The experimental protocols were similar to those described above, except that the TiO 2 suspensions were preconditioned with PFOS (500 mg/L) for at least 1 d before the H-acid adsorption, as described by Makarova et al [20].…”

“…The TiO 2 spectrum (Figure 4(a), 2) contained a band in the 1635 cm −1 region, characteristic of adsorbed water bending [20]. The FTIR spectrum of H-acid mixed with KBr (Figure 4(a), 1) was characterized by symmetric and asymmetric stretching bands of the sulfonic groups at 1043 and 1148-1221 cm −1 , respectively [20,23].…”

“…The TiO 2 spectrum (Figure 4(a), 2) contained a band in the 1635 cm −1 region, characteristic of adsorbed water bending [20]. The FTIR spectrum of H-acid mixed with KBr (Figure 4(a), 1) was characterized by symmetric and asymmetric stretching bands of the sulfonic groups at 1043 and 1148-1221 cm −1 , respectively [20,23]. In the spectrum of H-acid adsorbed on TiO 2 at pH 2.5 ( Figure 4(a), 5), the positions of these bands were influenced by different metal ions and, upon interaction with TiO 2 , the symmetric and asymmetric stretching vibrations of the sulfonic groups appeared at 1041 and 1155-1223 cm −1 , respectively.…”

Enhanced photocatalytic reduction of Hg(II) in aqueous medium by 2-aminothiazole-modified TiO2 particles

“…This modification also leads to the accumulation of trapped electrons and holes, permitting the injection of multielectrons into the sorbed metal, which is advantageous since multielectron transfers usually require lower reduction potentials than single electron transfers. [10][11][12] Another important factor is the enhanced sorption of mercury on the TiO 2 surface, which facilitates charge transfers from the TiO 2 to the sorbed mercury. 10 The present paper describes the preparation of titania chemically modified with 2-aminothiazole groups, its characterization, sorption studies and photocatalytic reduction of mercury (II) in aqueous medium.…”