Surface modification of TiO₂ nanoparticles for selective photodecomposition of nitrobenzene

Nitroaroaromatic compounds, e.g., nitrobenzene (NB), are of special interest since they are found in waste streams. Selective decomposition of the nitroaromatic compounds would be desirable to increase the rate of remediation and allow reuse or recycle of the less hazardous constituents. A study on the surface modification of TiO₂ particles with specific chelating agents that may enhance both TiO₂ redox properties and adsorption of nitroaromatic compounds for selective, photocatalytic removal of nitroaromatics from waste streams was carried out. NB adsorption and photodecomposition in the presence of phenol (Ph) over bare and arginine-modified nanocrystalline TiO₂ were carried out. The presence of arginine on TiO₂ colloids suppressed oxidation of Ph. When both NB and Ph were present in arginine modified colloids, a weakly resolved spectrum of hole localized on carboxyl group of arginine and electrons localized on the lattice trapping sites of TiO₂ nanoparticles were observed. Radical formation was reversible and no destruction of arginine occurred in agreement with chromatographic data. When NB was added to the arginine modified sample, the signal for trapped holes was altered indicating that the -NH- group participates in binding of NB, removing this site as a hole trapping center. This is an abstract of a paper presented at the 222nd ACS National Meting (Chicago, IL 8/26-30/2001).