RESUMO
The risk of the releasing of nanometric particles from construction materials with nanometric components might be one of the biggest threats to further development of them. One of the possible ingress routes to human organisms is the respiratory system. Therefore, it is crucial to determine the risk of emission of nanometric particles during material usage. In the presented paper, abrasion of mortar samples with nanometric TiO2 was investigated. A special abrasion test setup was developed to reflect everyday abrasion of the concrete surface of pavements. In the study, three TiO2-modifed mortar series (and respective reference series) underwent the developed test protocol and the grains were mobilized from their surface due to the applied load analyzed (granulation, morphology, and chemical composition). For a comparative analysis, an abrasion parameter was developed. Based on the obtained results, the modification of cementitious composites with nanometric TiO2 contributed to a reduction in the emission of aerosols and, therefore, confirmed the compatibility between TiO2 and cement matrix.
RESUMO
The application of photocatalytic materials has been intensively researched in recent decades. The process of nitric oxide (NO) oxidation during photocatalysis has been observed to result in the formation of nitric dioxide (NO2). This is a significant factor of the photocatalysis process, as NO2 is more toxic than NO. However, it has been reported that ozone (O3) is also formed during the photocatalytic reaction. This study analyzed the formation and oxidationof O3 during the photocatalytic oxidation of NO under ultraviolet irradiation using commercial photocatalytic powders: AEROXIDE® TiO2 P25 by Evonik, KRONOClean® 7050 by KRONOS®, and KRONOClean® 7000 by KRONOS®. An NO concentration of 100 ppb was assumed in laboratory tests based on the average nitric oxide concentrations recorded by the monitoring station in Warsaw. A mix flow-type reactor was applied in the study, and the appropriateness of its application was verified using a numerical model. The developed model assumed an empty reactor without a photocatalytic material, as well as a reactor with a photocatalytic material at its bottom to verify the gas flow in the chamber. The analysis of the air purification performance of photocatalytic powders indicated a significant reduction of NO and NOx and typical NO2 formation. However, no significant formation of O3 was observed. This observation was verified by the oxidation of pure ozone in the process of photocatalysis. The results indicated the oxidation of ozone concentration during the photocatalytic reaction, but self-decomposition of a significant amount of the gas.
