Triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) is commonly used as an antibacterial agent in various industrial products and is often detected in wastewater effluent. Comparison was made for triclosan degradation by photolysis and TiO2 photocatalysis (under UV irradiation (125 W)) based on analysis of transformation products, together with ecotoxicity evaluation. The morphology of the TiO2 was characterized by X-ray diffractometry (XRD) and field emission gun-scanning electron microscopy (FEG-SEM). Triclosan quantitation was performed by high performance liquid chromatography (HPLC). The optimal condition was obtained using a response surface model and desirability profile. The initial concentration of triclosan used in all the experiments was 10 mg L-1 to achieve comprehensive identification of transformation products. The optimal experimental condition was 30 mg L-1 TiO2 at pH 10. The photocatalytic system achieved > 99% triclosan degradation at 30 min of reaction. The mineralization rates by photolysis and photocatalysis were 25 and 90%, respectively. A total of 27 transformation products were identified using liquid chromatography quadrupole time of flight mass spectrometry (QTOF MS), being that 25 were new structures, not previously reported in the literature. Ecotoxicity assays demonstrated that triclosan and some of the major transformation products did not cause deleterious effects towards Lactuca sativa and Daphnia magna after 16 h of treatment.

Este estudo avaliou a eficiência do azul de metileno (AM) e do verde malaquita (VM) na inativação fotodinâmica (IFD) de Escherichia coli. Os fotossensibilizadores (FS) azul de metileno (1000 (mol L-1) e verde malaquita (250 (mol L-1) foram ativados com lâmpada de luz LED vermelha ((max = 636 nm). Suspensões bacterianas contendo 106 UFC mL-1 foram irradiadas por 5, 10 e 15 minutos (densidade de energia = 111,9 J cm-2, 223,9 J cm-2 e 335,8 J cm-2, respectivamente). As seguintes condições experimentais foram utilizadas para ambos os fotossensibilizadores: sem luz ou sem fotossensibilizador, somente luz, somente fotossensibilizador ou luz na presença do fotossensibilizador. Em seguida, diluições seriadas foram preparadas e semeadas em placas com meio PCA para determinação do número de UFC mL-1. Os resultados foram submetidos a análise de variância (ANOVA) e teste Tukey (P<0.05). A inativação fotodinâmica usando AM e VM foi efetiva na redução do crescimento de E. coli. A fotossensibilização do VM (250 µmol L-1) foi capaz de reduzir acima de 89% a contagem de células viáveis após 15 min de irradiação e o AM (1000 µmol L-1), no mesmo tempo de exposição, mostrou uma taxa de inibição de 94,6%. A lâmpada de LED vermelha utilizada se mostrou efetiva na fotossensibilização dos corantes e mostrou ser uma boa alternativa a fontes de luz convencional como o laser.

This study assessed the effectiveness of methylene blue (MB) and malachite green (MG) on photodynamic inactivation (PDI) of Escherichia coli. The photosensitizers methylene blue (1000 (mol L-1) and malachite green (250 (mol L-1) were activated with a red light-emitting diode (LED) lamp ((max = 636 nm). Bacterial suspensions containing 106 CFU mL-1 were irradiated for 5, 10 and 15 minutes (energy density = 119.9 J cm-2, 223.9 J cm-2 and 335.8 J cm-2, respectively). The following experimental conditions were performed for each photosensitizer: no light irradiation or photosensitizer, irradiation only, photosensitizer only or irradiation in the presence of a photosensitizer. Next, serial dilutions were prepared and seeded onto PCA medium for the determination of the number of colony-forming units per milliliter (CFU mL-1). The results were subjected to analysis of variance (ANOVA) and Tukey test (P<0.05). Photodynamic inactivation using MB and MG was effective in reducing the number of E. coli. Malachite green (250 µmol L-1) photosensitization was able to achieve reductions of over 89% in the viable counts after 15 min of irradiation and methylene blue (1000 µmol L-1), at the same conditions of irradiation, showed a rate growth inhibition of 94.6%. The red LED light used has proven to be effective in the photosensitizing dyes and proved a good alternative to conventional light sources such as laser.

Neste trabalho, a degradação de cânfora em solução aquosa foi avaliada utilizando-se processos fotocatalíticos mediados por suspensões e formas imobilizadas de TiO2 e ZnO. Os catalisadores suportados (TiO2/anéis de vidro, TiO2/alginato de cálcio e ZnO/alginato de cálcio) foram caracterizados por microscopia eletrônica de varredura com espectroscopia de energia dispesiva de raios X (SEM/EDX), difratometria de raios X (XRD), fluorescência de raios X por energia dispersiva (EDXRF) e espectroscopia Raman, técnicas que permitiram confirmar a elevada porosidade dos materiais, assim como as fases cristalinas características (anatase e wurtzita). A eficiência de degradação dos fotocatalisadores suportados foi comparada com a dos semicondutores em suspensão, observando-se resultados comparáveis entre TiO2 Degussa P25 e TiO2 imobilizado em anéis de vidro. Por outro lado, o uso de esferas de alginato de cálcio propiciou menores eficiências de degradação, provavelmente em decorrência da significativa redução da área superficial nos sistemas imobilizados.

In this work, the degradation of aqueous solution of camphor by heterogeneous photocatalysis was study using suspended and supported TiO2 and ZnO. The supported catalysts (TiO2/borosilicate reaching ring, TiO2/calcium alginate and ZnO/calcium alginate) were characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX), X-ray diffractometry (XRD), energy dispersive X-ray fluorescence (EDXRF) and Raman spectroscopy, techniques that permitted to confirm the porosity of the material as well as the characteristic crystalline forms (anatase and wurtzite). The degradation efficiency of the supported photocatalysts was compared with the performance of free TiO2 and ZnO, observing comparable results between conventional Degussa P25 TiO2 and TiO2 immobilized in glass-rings. On the other hand, the use of calcium alginate beads leads to lower degradation efficiency probably due to the significant area reduction observed in immobilized systems.