Photocatalytic removal of organic dyes by titanium doped alumina nanocomposites: Using multivariate factorial and kinetics models

Hazardous containing different groups of dyes from various industries are extremely dangerous and causing unfavorably susceptible dermatitis, skin diseases, transformation, and malignant growth. To overcome the hazards caused by water pollution, eco-friendly composites (TiO2-Al2O3) of titanium oxide (TiO2) and alumina (Al2O3) were synthesized with different proportional ratios (0.25/1, 0.16/1, 0.125/1, and 0.1/1) by kneading method and characterized through X-ray diffraction, scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet-Visible (UV-Vis) spectrophotometry and high resolution transmittance electron microscopy (HR-TEM). Experimental finding showed that the sample TiO2 / Al2O3 with a molar-ratio of 0.1/1 had the higher photodegradation efficacy for malachite green and from the ratio 0.1/1, the higher photodegradation efficiency was achieved for eosin Y. The comparative studies of TiO2-Al2O3 samples were done for basic malachite green and acidic eosin Y and it was estimated that due to adsorbent, Al2O3 surface basicity it showed the highest adsorption for acidic eosin Y and hence had a higher photo degradation removal up to 90% for the eosin Y than for the basic malachite green with 80% photo degradation removal. Reaction mechanism for photodegradation were finest to define by Langmuir isotherms which trailed by pseudo-second order kinetics. The t/q(t) vs t plots for pseudo-second order kinetic produced high regression coefficients (R-2 = 0.963), which stated the adsorbate sorption's followed the pseudo second order kinetics. Thermodynamic parameters of dye degradation were calculated by the Van't Hoff equation that indicated the adsorption method was exothermic. The Delta H parameters were found to be -54.44 kJ mol(-1). The negative Delta H recommended the exothermic biosorption process. Residuals plots for responses, interaction plots for responses and inter-contour plots were utilized to study the optimum points. Furthermore, accredited to experimental results and a reaction mechanism is planned for the photodegradation of organic dyes with TiO2-Al2O3 photocatalyst. Thus the broad band gap of inert semiconductor TiO2 can be narrower by heterogeneous coupling with Al2O3 through kneading method and showed the excellent photodegradation of organic dyes in the visible region without producing any secondary pollutant. (c) 2023 Elsevier B.V. All rights reserved.