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Factorial Design of Experiments for Optimization of Photocatalytic Degradation of Tartrazine by Zinc Oxide (ZnO) Nanorods with Different Aspect Ratios

preprint
submitted on 04.04.2020, 09:13 and posted on 06.04.2020, 10:15 by Andrew Skinner, Anthony DiBernardo, Arvid Masud, Nirupam Aich, Alexandre Pinto
The photocatalytic degradation of the azo dye tartrazine using zinc oxide (ZnO) as photocatalyst under ultraviolet light was investigated using a 24 factorial design. The variables studied were the aspect ratio of ZnO nanorods, the ZnO load, the initial pH of tartrazine solution, and the H2O2 volume. These variables were studied aiming to maximize the tartrazine removal efficiency and the pseudo-1st-order rate constant of the removal process. The ZnO aspect ratio was tuned by varying the Lewis base during the synthesis, hexamethylenetetramine (HMTA) was used to prepare ZnO with low aspect ratio (ZnO_LowAR), and NaOH was used to prepare ZnO with high aspect ratio (ZnO_HighAR). The microstructural characterizations indicated that ZnO_LowAR and ZnO_HighAR nanorods have similar structural, textural and optical properties. The only exception was the dimensions of the nanorods obtained, which could result in differences in the facets exposed on each type of nanorod surface. The factorial design revealed that ZnO aspect ratio, the initial pH of tartrazine solution, and the H2O2 volume all have primary significant effects, whereas the ZnO load is not significant neither in the tartrazine removal efficiency nor in the pseudo-1st-order rate constant. Statistical models considering the coefficients of the significant interactions were obtained, leading to reasonable predicted results in comparison to the results experimentally obtained. The conditions leading to highest removal efficiency (~92%) and pseudo-1st-order rate constant (3.81 x 10-2 min-1) were carried out with ZnO_HighAR, initial pH 7, and without H2O2, which outperformed the TiO2 P-25 under the same conditions.

History

Email Address of Submitting Author

alex.pinto@manhattan.edu

Institution

Manhattan College

Country

United States

ORCID For Submitting Author

0000-0001-9584-8183

Declaration of Conflict of Interest

The authors declare no conflict of interest

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