Filme polimérico fotocatalítico a base de polímero biodegradável com TiO2 para degradação do corante vermelho BF-4B

Abstract

Due to environmental pollution from textile industries, there has been interest in removing dyes from processes such as dyeing and washing. In this context, the application of polymeric fibers electrospun with TiO2 in the photodegradation of the dye Red BF-4B was studied. To produce the polymeric yarns, the polymer blend PBAT/PLA and TiO2 nanoparticles were used. The polymer solution was formed by dissolving the polymer (15% m/v) in a solvent mixture of chloroform and dimethylformamide (85:15% v/v) and finally adding the TiO2 nanoparticles (10% m/v) ). The fibers were electrospinned using the conditions of flow of 1.80 mL h-1, distance of 16 cm and voltage of 18 kV. The fibers obtained were characterized by morphological, structural and thermal techniques, then the photocatalytic tests were carried out and, finally, the viability of the polymeric film was evaluated after the photocatalytic process. PBAT/PLA/TiO2 fibers have cylindrical morphology with an average diameter of 1.12±0.26 μm, in addition they are rough and have small bumps along their lengths due to the presence of TiO2. By TEM analysis, it is possible to verify the dispersion of TiO2 nanoparticles along the fibers, and it is noted that the polymer surrounds them by a thin layer. Both fibers with and without TiO2 have a hydrophobic character at the beginning of the contact angle wettability analysis, but after 75 min the wettability increases due to physical mechanisms such as wetting and encrustation. The FTIR spectra show characteristic functional groups of PBAT and PLA polymers and in the fibers with TiO2 nanoparticles it is observed in the region between 1000 and 650 cm-1 Ti-O-Ti oscillations dominant over the characteristic bands of the polymer. In PBAT/PLA and PBAT/PLA/TiO2 fibers, the presence of an amorphous halo characteristic of PBAT/PLA polymer blends can be seen in X-ray diffractograms. Thermal analysis indicates a conformational change, so that the PLA polymer demonstrates greater stability, as opposed to the PBAT polymer, which became easier to be degraded. The pHpcz of the materials indicates that for anionic dyes such as BF-4B Red, a pH below 7.42 would facilitate the catalytic process. Furthermore, the mathematical adjustments indicate that at the beginning of the reaction, the kinetic model that best fits the experimental data is the zero-order model, then, at lower concentrations, the model becomes the pseudo-first-order model. The reuse of polymeric film showed good removals (86.60 to 93.07%) during six cycles of 600 min. After the photocatalytic process, in the first and sixth degradation cycle, the fibers remain cylindrical, with prominent protrusions, the presence of several fractured fibers and a reduction in their diameters, indicating degradation and wear of the polymer. Infrared vibrational spectra show that most of the functional groups did not change, except for the regions at 1755 (C=O) and 1714 cm-1 (C-O), showing a possible conformational alteration of the polymeric chains. The thermal degradation profiles also changed, but the maximum thermal decomposition temperatures showed few changes after the photocatalysis process and the thermal degradation began to increase slightly after the cycles. Furthermore, by X-ray diffractograms it is observed that TiO2 particles are more exposed after photocatalysis, demonstrating loss of polymeric material during this process. Thus, it is emphasized that PBAT/PLA fibers produced by the electrospinning technique are promising to be used as support material for the photocatalyst (TiO2) and application in the treatment of textile dye residues.