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Titanate nanotubes were synthesized and subjected to an ion exchange reaction with erbium salt aqueous solution to obtain titanate nanotubes exchanged with erbium (3+) ions. In order to evaluate the effects of the thermal treatment atmosphere on the structural and optical properties of erbium titanate nanotubes, we subjected them to heat treatment in air and argon atmospheres. For comparison, titanate nanotubes were also treated in the same conditions. A complete structural and optical characterizations of the samples was performed. The characterizations evidenced the preservation of the morphology with the presence of phases of erbium oxides decorating the surface of the nanotubes. Variations in the dimensions of the samples (diameter and interlamellar space) were promoted by the replacement of Na+ by Er3+ and the thermal treatment in different atmospheres. In addition, the optical properties were investigated by UV–Vis absorption spectroscopy and photoluminescence spectroscopy. The results revealed that the band gap of the samples depends on the variation of diameter and sodium content caused by ion exchange and thermal treatment. Furthermore, the luminescence strongly depended on vacancies, evidenced mainly by the calcined erbium titanate nanotubes in argon atmosphere. The presence of these vacancies was confirmed by the determination of Urbach energy. The results suggest the use of thermal treated erbium titanate nanotubes in argon atmosphere in optoelectronics and photonics applications, such as photoluminescent devices, displays, and lasers.

This paper aimed to develop a new photocatalytic reactor design with a rotary tree branch structure for wastewater treatment in the textile industry. The brass sheet calcined at 500 °C (B500) was used as the photocatalyst and as a substrate for ZnO nanoparticle immobilization (B500ZnO). The photoreactor performance was evaluated toward the photodegradation of an aqueous solution of Reactive Black 5 dye (AS-RB5), raw wastewater (RW), and treated wastewater (TW). X-ray diffraction (XRD) and scanning electron microscopy (SEM) results illustrated ZnO nanowire formation over B500 and B500ZnO substrates. The bandgap values of these samples were estimated by diffuse reflectance measurements. The effects of dye concentration, the type of radiation, and ZnO NP deposition on the degradation of AS-RB were evaluated. Decreases in chemical oxygen demand (COD) greater than 82% were obtained using solar irradiation and artificial light as the energy source. Regarding calcined brass sheet reutilization, a decrease of 45% in the photocatalytic activity efficiency after 5 cycles was noted due to the effect of photocorrosion of the ZnO nanowires. The photoreaction of the RW and TW effluents showed COD values of 21 and 35%, respectively, which are below the limits established by state environmental control. With respect to RB5 addition to the TW effluent (TW-RB5), a discoloration of 62% was noticed after 3 h of photodegradation. Furthermore, the toxicity tests of the AS-RB5 and TW-RB5 samples did not display toxic intermediates after the photoreaction since 80% of the seeds germinated. Finally, the photoreactor exhibited good performance regarding the decrease in effluent pollutant charge, in addition to the efficient discoloration of RB5 dye.

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Rigid polyurethane foams were prepared by the one-step expandable foam method using casting molding followed by forming clay-based composites. Polyurethane/vermiculite foam composites (PU/VMT) were controlled based on adding the percentage of clay in the formulation. The effects of composite modifications were evaluated by X-ray diffraction (XRD), thermogravimetric analysis (TG/DTG), and scanning electron microscopy (SEM/EDS) applied to the flame retardancy explored by the vertical burn test. The results indicated that adding clay controlled the particle size concerning polyurethane (PU) foams. However, they exhibited spherical structures with closed cells with relatively uniform distribution. XRD analysis showed the peaks defined at 2θ = 18° and 2θ = 73° relative to the crystallinity in formation and interaction of rigid segments were identified, as well as the influence of crystallinity reduction in composites. In the flame test, the flame retardant surface was successful in all composites, given the success of the dispersibility and planar orientation of the clay layers and the existence of an ideal content of vermiculite (VMT) incorporated in the foam matrix.

TiO2/Karaya composite was synthesized by the sol-gel method for the photoinactivation of pathogens. This is the first time that we have reported this composite for an antimicrobial approach. The structure, morphology, and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-rays (EDS), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance, and the surface area was characterized by the BET method. The XRD and EDS results showed that the TiO2/Karaya composite was successfully stabilized by the crystal structure and pore diameter distribution, indicating a composite of mesoporous nature. Furthermore, antibacterial experiments showed that the TiO2/Karaya composite under light was able to photoinactivate bacteria. Therefore, the composite is a promising candidate for inhibiting the growth of bacteria.

This paper aimed to develop a new photocatalytic reactor design with a rotary tree branch structure for wastewater treatment in the textile industry. The brass sheet calcined at 500 °C (B500) was used as the photocatalyst and as a substrate for ZnO nanoparticle immobilization (B500ZnO). The photoreactor performance was evaluated toward the photodegradation of an aqueous solution of Reactive Black 5 dye (AS-RB5), raw wastewater (RW), and treated wastewater (TW). X-ray diffraction (XRD) and scanning electron microscopy (SEM) results illustrated ZnO nanowire formation over B500 and B500ZnO substrates. The bandgap values of these samples were estimated by diffuse reflectance measurements. The effects of dye concentration, the type of radiation, and ZnO NP deposition on the degradation of AS-RB were evaluated. Decreases in chemical oxygen demand (COD) greater than 82% were obtained using solar irradiation and artificial light as the energy source. Regarding calcined brass sheet reutilization, a decrease of 45% in the photocatalytic activity efficiency after 5 cycles was noted due to the effect of photocorrosion of the ZnO nanowires. The photoreaction of the RW and TW effluents showed COD values of 21 and 35%, respectively, which are below the limits established by state environmental control. With respect to RB5 addition to the TW effluent (TW-RB5), a discoloration of 62% was noticed after 3 h of photodegradation. Furthermore, the toxicity tests of the AS-RB5 and TW-RB5 samples did not display toxic intermediates after the photoreaction since 80% of the seeds germinated. Finally, the photoreactor exhibited good performance regarding the decrease in effluent pollutant charge, in addition to the efficient discoloration of RB5 dye.