Photocatalytic degradation of Novacron blue and Novacron yellow textile dyes by the TiO2/palygorskite nanocomposite.

The photocatalytic discoloration of industrial dyes, Novacron blue (NB) and Novacron yellow (NY), was investigated using composites based on TiO2 and natural palygorskite (Pal-Ti10 and Pal-Ti30). The method consisted of synthesizing the composites starting from a physical mixture of TiO2 and natural palygorskite in the presence of alcohol, for impregnation through calcination under conditions of temperature equal to 450 °C and atmospheric air. The characterization techniques used in this work were FTIR, XRD, XRF, SEM, particle size analysis and zeta potential. The photocatalysis for the NB dye was investigated through the application of a factorial 24 experimental design, aiming at the best experimental conditions and finally applying them in another NY industrial dye. The investigated concentrations of NB were 10 ppm and 30 ppm, the composites were synthesized using 10 and 30% (p/p) of titanium dioxide in palygorskite, the two pH values were 2.0 and 6.0 and the light intensities 9 and 18 W were used. Tests performed at pH 2.0, Pal-Ti30 composite, power 18 W and 10 ppm of dye showed 100% color removal of both dyes in 90 min. The bleaching process followed the pseudo-first order kinetic model, and the apparent constants (Kapp) were 0.0216 min-1 and 0.0193 min-1 for NB and NY dyes, respectively. The results of total organic carbon (TOC) showed mineralization of 61.70% and 58.06% for NB and NY, respectively, in 90 min of treatment, and the by-products were detected by GC-MS.

Experimental design for optimization of the photocatalytic degradation process of the remazol red dye by the TiO2/expanded perlite composite.

In this study, the photocatalytic decolorization of remazol red dye (RR) was evaluated using TiO2 based composites supported on the expanded perlite (T-EP-10% and T-EP-30%). The characterization techniques used in this work were IR, XRD, XRF and particle size analysis. In order to optimize the RR discolouration process, a factorial planning was applied. The best experimental conditions are the RR initial concentration of 10 mg L-1, composite T-EP-30% and both PHs showed positive results in the decolorization. The tests performed at pH 2.0 showed 100% removal of RR colour in 180 min and at pH 5.0 100% colour removal was obtained in 120 min. The decolorization process follows a pseudo first-order-kinetics, the kapp of 0.01191 min-1 for the tests at pH 5.0 and 0.00812 min-1 for the tests at pH 2.0. The results of energy cost shown that in both pH 2.0 and 5.0 tests were feasible in efficiency and economically. The energy consumption for the test at pH 2.0 was 0.297 kWhdm3 and final cost of R$ 0.163, while the energy consumption for the test at pH 5.0 was 0.198 kWhdm3 and a final cost of R$ 0.111.

Obtaining and Applying Nanohybrid Palygorskite-Rifampicin in the pH-Responsive Release of the Tuberculostatic Drug.

Despite having good efficacy in the treatment and prevention of tuberculosis, the administration of rifampicin (RIF) can cause serious side effects, resulting from the prolonged use of this substance. Thus, it is necessary to seek new systems for administering tuberculostatic drugs, to avoid unwanted adverse effects, increase their bioavailability and, consequently, improve their therapeutic efficacy. The present work describes the achievement of a pH-responsive system for RIF, using palygorskite, a fibrous clay mineral, as a nanocarrier. To evaluate the influence of some operational variables on the drug adsorption process, a 24 factorial experimental design was used. The experiment using a maximum concentration (0.125 mg/mL), lower mass of PAL (300 mg), and lower pH (pH 2) was more efficient compared to other experiments, resulting in a higher dose of the incorporated drug, equivalent to 33.62 mg/g. To elucidate the mechanism of interaction between the materials, the hybrid obtained was characterized by different characterization techniques (Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry/derived thermogravimetry, zeta potential, scanning electron microscopy, and dispersive energy spectroscopy). In addition, kinetic models and adsorption isotherms were applied to the experimental data. Through in vitro release studies, it was possible to verify the effectiveness of the pH-dependent system obtained. The adjustment of experimental release data to the theoretical model of Higuchi indicated that the release of rifampicin occurs in a prolonged way from the palygorskite.