Crissie Dossin Zanrosso

Polymeric composite films have been explored for many photocatalytic applications, from water treatment to self-cleaning devices. Their properties, namely, thickness and porosity, are controlled mainly by the preparation conditions. However, little has been discussed on the effect of thickness and porosity of polymeric composite films for photocatalytic processes, especially in gas phase. In the present study, different preparation treatments of ZnO-based polymeric composite films and their effects on its performance and stability were investigated. The polymeric composites were prepared by solution mixing followed by non-solvent induced phase separation (NIPS), using poly(vinylidene fluoride) (PVDF) as the matrix and ZnO-based photocatalysts. Different wet thickness, photocatalyst mass, and treatments (e.g., using or not pore-forming agent and compatibilizer) were assessed. A low ZnO/PVDF ratio and higher wet thickness, together with the use of pore-forming agent and compatibilizer, proved to be a good strategy for increasing photocatalytic efficiency given the low agglomerate formation and high polymer transmittance. Nonetheless, the composites exhibited deactivation after several minutes of exposure. Characterization by XRD, FTIR-ATR, and SEM were carried out to further investigate the polymeric film treatments and stability. ZnO film was most likely deactivated due to zinc carbonate formation intensified by the polymer presence.

Heterogeneous photocatalysis represents a solution for several environmental problems. However, achieving photocatalyst separation from reaction media on a large scale remains a challenge, one that might be overcome by the immobilization of photocatalysts into supports. To this end, composites of polyvinylidene fluoride and zinc oxide (ZnO) were prepared by three different techniques: solution mixing (SM) followed by Nonsolvent Induced Phase Separation; and melt blending at both low‐ and high‐shear rates (LS and HS) in a rheometer and mixing chamber, respectively, to compare the resultant morphology in photocatalysis. Photocatalytic efficiency was assessed by methylene blue (MB) discoloration in a batch reactor liquid phase and by resazurin (RZ) reduction. The changes promoted by nanoparticle inclusion, processing conditions and UV effect were demonstrated by FTIR‐ATR, XRD, DSC, and SEM. Results showed that ZnO incorporation was successful under all processing conditions, providing effective photocatalytic composites. However, samples prepared by SM had a twofold increase in discoloration efficiency and fourfold increase in surface photoactivity, when compared with LS or HS‐produced samples, explained by its higher porosity of 88% ± 1.3%. The covering of the photocatalyst surface was also evident on SEM analysis for melt blended samples, further contributing to reduction in their photocatalytic activity.

Despite the efforts of the scientific community, carrying out photocatalyst immobilization so that industrial application of photocatalysis becomes economically feasible is still a challenge to be overcome. In this work, polyvinylidene fluoride (PVDF)/ZnO composites were prepared by solution mixing based on solid knowledge of membrane technology and with the help of a powerful experimental design for systematic evaluation of the interaction among variables. A strategy for variable screening was used, followed by a complete evaluation at two levels, leading to predictive models. As a result, photocatalyst amount, pore agent concentration, and wet thickness were the most significant in the target molecule discoloration. With this, it was possible to obtain a 40 and 186% enhancement in photocatalytic efficiency compared to previous results and simple photolysis, respectively. Finally, the samples were characterized by FTIR‐ATR, XRD, and SEM and chemical, crystalline and morphological differences were observed both with nanoparticle and pore agent incorporation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48417.

A presente pesquisa trata da qualificação didático-pedagógica de professores engenheiros a partir de um aporte teórico. Um levantamento da qualificação docente foi realizado para diagnóstico dos cursos de engenharia química das Instituições de Ensino Superior (IES) do Rio Grande do Sul, a partir de informações contidas no currículo Lattes. Variáveis como gênero, titulação e natureza da instituição foram cruzadas estatisticamente com a qualificação docente. Além disso, buscou-se correlacionar estes dados ao desempenho dos alunos através do Exame Nacional de Desempenho de Estudantes (ENADE) e do crescimento médio no número de formandos. Os resultados sugerem que a qualificação dos professores poderia ser aprimorada. Ainda, há mais professores qualificados nas IES privadas do que nas públicas. Por fim, verificou-se que as IES com os maiores números de docentes com qualificação didático-pedagógica apresentaram também o maior crescimento no número de formandos nos últimos cinco anos.

The immobilization of photocatalysts on several kinds of substrates has been widely studied over the past few years, focusing mainly on improving its industrial application. In this work, novel hybrid films were prepared, employing TiO₂ P25, commercial ZnO or BiOI, synthetized through hydrothermal method and immobilized on poly(vinylidene fluoride) by the non‐solvent‐induced phase inversion technique. Subsequently, the prepared composites were evaluated by photodegradation of methylene blue (MB) under ultraviolet or visible light. The samples were also characterized by scanning electron microscope, thermo‐gravimetric analysis, attenuated total reflection–Fourier transform infrared spectroscopy, and X‐ray diffractometer analysis to improve comprehension of the composites' photocatalytic behavior. The degradation reaction of the contaminants exhibited pseudo‐first order kinetics in all samples, and achieved better performance when compared to simple photolysis. The recyclability of the hybrid films was also evaluated and proved that polymeric matrix is a promising material for the preparation of composites for photocatalysis applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46367.