Heterogenization of water-soluble porphyrins in Ti/TiO2 nanotubes electrodes: experimental and theoretical insights for atrazine degradation

Pollutant degradation has been a very important topic in environmental research. The present paper presents an approach to degrade atrazine, an environmentally harmful herbicide that has been widely used in the agriculture industry. Ti/TiO2 nanotube electrodes modified by porphyrins were prepared for photolysis, photocatalysis, and photoelectrocatalysis (PEC) applications. Manganese- and free base porphyrin were studied, and it was possible to verify the kinetic model more suitable for each system. Unfortunately, Mn-porphyrins had an inhibitory effect on the ATZ degradation activity by Ti/TiO2 nanotube electrodes. Although the Ti/TiO2-free base porphyrin under the PEC experiment (using surface water from a Brazilian river) did not lead to the best degradation system, we could verify the formed products, which have been not described for other porphyrin-mediated atrazine degradation, are equal or more toxic than the original atrazine. We highlight the importance of verifying the products formed in the degradation systems and determining their toxicities.