Membranas poliméricas incorporadas com dióxido de titânio e óxido de ferro para fotocátalise de corante

Abstract

The population growth and the new habits of the population result in an increase in the amount of waste generated and discharged in the environment, promoting air, soil and water pollution (6). Among the pollutants, textile dyes stand out, which have undesirable characteristics to the environment, even in minimal concentrations (7). Thus, this work aims to use heterogeneous photocatalysis for the degradation of Reactive 195 red dye, commercially known as Reactive Red BF-4B, using the semiconductors Titanium-rutile dioxide (TiO2-R) and iron oxide-magnetite (OFM) incorporated in a polymeric membrane produced with the compostable and biodegradable polymer commercially known as Ecovio® (polymer blend composed of poly (butylene adipate co-terephthalate) (PBAT) and poly (lactic acid) (PLA) obtained by electrospinning. The parameters for the electrospinning of polymeric membranes were: distance between the tip of the capillary needle and the 12 cm collecting target, flow rate of 1 mL / h and potential difference (ddp) of 14 kV. The electrospinning temperature was maintained at 22 ºC and the relative humidity between 35% and 45%. To evaluate the best mass proportions of the TiO2-R / OFM semiconductors, an experimental design 22 was carried out, using as a response the degradation of the Reactive Red BF-4B dye. The values obtained were: 10% TiO2-R, 1% OFM and pH 7.0, with degradation of approximately 64% in 24 hours. The obtained membrane was characterized using Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (DRX), Thermogravimetric Analysis (TGA), Infrared with Fourier Transform (FTIR) and Contact Angle. The analyzes showed that the semiconductors were incorporated and that they are possibly found inside the polymeric membranes. In addition, SEM analyzes showed a decrease in the fiber diameter of the pure Ecovio® membrane from 0.9466 ± 0.2490 μm to 0.6706 ± 0.1447 μm in the fibers of the membrane incorporated with the semiconductors TiO2-R / OFM. With the contact angle measurements, the information was obtained that the incorporated membrane had a hydrophobic surface, with an angle of approximately 121.45 ± 1.44º. Due to the hydrophobicity of the polymeric membrane surface and the previous results, which showed that the semiconductors are possibly found inside the membranes, a basic treatment was carried out with a NaOH solution, in order to make the polymeric membrane more hydrophilic, improving the contact of semiconductors with the reaction medium and consequently increasing the catalytic efficiency of the process. With the basic treatment, the membrane started to degrade 94.0% of the dye in 24 hours. The treated membranes were characterized again by the techniques of SEM, FTIR, TGA, DSC and DRX. The results obtained were similar to the previous ones, however, it was observed in the XRD technique an increase in the intensity of the polymeric membrane peaks indicating a possible basic hydrolysis in the polymers leaving the TiO2-R / OFM semiconductors more exposed and changes in the membrane wettability, with contact angles of approximately 80.68 ± 1.52° after treatment with base. The potential for reuse of the incorporated and treated polymeric membrane was also evaluated, carrying out a study with 4 degradation cycles. As a result, degradation values greater than 80% were obtained after 24 hours in all degradation experiments. After this study, an analysis of the degradation kinetics for the dye was carried out, which showed a pseudo-first order kinetic model which shows that the system depends on the concentration of the BF-4B Red dye solution. Thus, the membrane showed promise for degradation of the red dye BF-4B, presenting good degradation, easy removal and reuse of the membrane.