Abstract
This work investigated the relation between direct band-gap conversion and excitation wavelength towards catalysis efficiency in red, green, and blue (RGB) light-emitting diode (LED) reactors. An integrating sphere and spectroradiometer system obtained the emission wavelengths of the operating modes spectra of the RGB-LED reactors. The effects of pH, catalyst, and H2O2 dosage were investigated, and the optimal photocatalysis conditions were found to be at pH 3, catalyst loading of 0.25 g L−1, 0.25 mmol L−1 of H2O2(aq) (30% v/v) for an initial model pollutant concentration of 75 mg L−1 and reaction time of 60 min. Under the higher intensity red mode (R1), the highest color removal rate was reached (88.1%), while in the conventional white light mode (WL), the decolorization efficiency remained 64.3%. Furthermore, the R1 mode showed a superior TOC removal than the WL mode, reaching the final removal efficiencies of 91.86% and 61.06%, respectively. Contrary to what has been reported, as the dominant wavelength of the irradiation source decreased, the efficiency also tended to decrease. The electron-hole recombination increased as the irradiation mode decreased, and a work function (φ) representing this phenomenon was obtained by the deduction of the relation between energy (E) and frequency (f) of the photons involved. Therefore, the insights presented in this work are valuable tools in increasing LED photocatalysis efficiency.
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