RESUMO
In this work, photocatalytic materials constituted by Cr-doped TiO2 (Cr-TiO2) decorated with noble metals show high effectiveness in the mineralization of Acid Orange 7 (AO7) and in the disinfection of real river water. The materials were firstly obtained by sol-gel method to get Cr-TiO2 that was subsequently modified by photochemical deposition of Ag or Pd nanoparticles (Ag/Cr-TiO2, Pd/Cr-TiO2). Chemical-physical characterization results evidenced that the noble metals were homogeneously distributed on the Cr-TiO2 surface. By using Pd(0.25%)/Cr-TiO2, the AO7 discoloration efficiency was about 91.4% after only 60 min of visible irradiation, which can be due to the lowest band gap of this material. Moreover, nitrates, chlorides, total hardness, and coliform bacteria content significantly decreased after the treatment of real river water samples (that is contaminated by industrial and domestic effluents) under UV and visible light irradiation in the presence of TiCrOx decorated with noble metals. One hundred percent of elimination rate for E. coli, total coliforms, and other enterobacteriaceae (without regrowth) was achieved by using Ag/Cr-TiO2 as photocatalyst.
RESUMO
The photo-Fenton process application to eliminate carbapenem-resistant Klebsiella pneumoniae, an antibiotic-resistant priority pathogen, was evaluated. Initially, reagents concentration effect was tested and under suitable conditions (5â¯mgâ¯L-1 of Fe2+ and 50â¯mgâ¯L-1 of H2O2) complete bacteria inactivation by action of hydroxyl radical and UVA plus hydrogen peroxide was achieved at 120â¯min. The process presented a strong residual disinfecting effect when light was turned off at only 20â¯min. Besides, the cultivability of treated K. pneumoniae in a selective medium containing carbapenem antibiotics was considered. bla-KPC, gene responsible for the resistance, evolution was also assessed. The bacteria response to carbapenem antibiotics was higher as the treatment time increased. In turn, bla-KPC gene remained when K. pneumoniae was completely inactivated (120â¯min); nevertheless, treatment times longer than 120â¯min diminished bla-KPC presence. Finally, the photo-Fenton process and its modifications (citric acid addition or persulfate anion instead hydrogen peroxide) were applied to a real hospital wastewater in Colombia. In such complex matrix, the conventional photo-Fenton system reached a moderate disinfection (â¼3.5 log-units at 300â¯min). Meanwhile, in presence of citric acid total inactivation was completed at the same time. Interestingly, the H2O2 substitution by persulfate strongly accelerated the microorganism elimination, achieving the 6-log-units reduction after only 60â¯min of process action. Thus, the effective elimination of K. pneumoniae from water by the modified photo-Fenton evidenced the potential applicability of this process to limit the proliferation of antibiotic resistant bacteria.