Degradation of leaf green food dye by heterogeneous photocatalysis with TiO2 over a polyethylene terephthalate plate

This work presents a study of the removal of leaf green dye by photocatalysis using TiO2 in suspension and immobilized on polyethylene terephthalate (PET) plates. SEM, diffuse reflectance and XRD analyses confirmed the presence of the catalyst on the PET support and FTIR analyses proved that the catalyst remained on the support after treatment. Preliminary tests with UV-C/TiO2(susp.)/H2O2 system showed a degradation of 97% of dyes in 360min. In the kinetic study, 98% degradation was obtained for the UV-C/TiO2(susp.)/H2O2 system and 90% for the UV-C/TiO2 (PET)/H2O2 system in 240min. This result demonstrated the efficiency of employing TiO2 (PET) in the process of the contaminant when compared with TiO2(susp.). The reaction kinetics was fitted to a pseudo-first-order model, obtaining a kinetic constant of 0.0164 in the UV-C/TiO2(susp.)/H2O2 treatment and 0.0094min(-1) in the UV-C/TiO2(PET)/H2O2 treatment. Kinetic data for the dye solution for the UV-C/TiO2(susp.)/H2O2 and UV-C/TiO2 (PET)/H2O2 systems were modeled using neural networks to predict contaminant concentration over time. In the phytotoxicity assays, the IC50 of the treated samples increased in the UV-C/TiO2(PET)/H2O2 and UV-C/TiO2(susp.)/H2O2 systems compared to the initial dye solution, suggesting a decrease in dye toxicity. The UV-C/TiO2(PET)/H2O2 system exhibited more than 70% of organic matter (COD) removal and 52% of mineralization (TOC). TiO2 immobilization exhibited degradation rates close to those of the TiO2 suspension system.