Direct photoconversion of nitrite to dinitrogen on Pd/TiO2 coupled with photooxidation of aquatic pollutants

Nitrate (NO3-) and nitrite (NO2-) are ubiquitous aquatic pollutants and should be controlled for water quality. Although diverse methods of nitrate/nitrite reduction have been developed, most require chemical reductants and external energy inputs. Nitrite is oxidized by photogenerated hydroxyl radicals (center dot OH) in an aqueous sus-pension of Pd-loaded TiO2 (Pd/TiO2) with producing nitrate as a major product. The main photoconversion product of nitrite is changed from nitrate to N-2 on Pd/TiO2 in the presence of aquatic pollutants (arsenite (As (III)) or 4-chlorophenol (4-CP)) which can suppress the photooxidation of NO2- by scavenging holes/center dot OH. The photogenerated H-2 on Pd/TiO2 serves as a main reductant and was immediately consumed for reducing nitrite to N-2. The presence of As(III) or 4-CP also enhanced the durability of Pd/TiO2 by efficiently scavenging hole/center dot OH that may oxidize Pd nanoparticles. The proposed process can be a viable treatment option for nitrite-contaminated water containing various aquatic pollutants.

Automated summary

Nitrate (NO3-) and nitrite (NO2-) are common water pollutants and need to be controlled for water quality. A method using Pd-loaded TiO2 (Pd/TiO2) in an aqueous suspension has been developed for the conversion of nitrite to nitrate. The presence of aquatic pollutants such as arsenite (As (III)) or 4-chlorophenol (4-CP) can change the main photoconversion product from nitrate to N-2 and enhance the durability of Pd/TiO2. This process can be a viable treatment option for nitrite-contaminated water with various aquatic pollutants.