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.