The Effect of Electronic and Optical Properties on the Kinetic Photocatalytic Model of Methyl Blue Degradation

TL;DR

This study examines how light properties affect the breakdown of a dye using a photocatalyst, finding that UV light from a mercury lamp improves the process.

Contribution

A new kinetic photocatalytic model is proposed that incorporates effective irradiance, quantum yield, and reactant coverage.

Findings

The low-pressure Hg lamp enhanced MB photodegradation due to UV radiation and Ag nanoparticle effects.

High effective irradiance increases photocatalytic activity by generating more electron-hole pairs.

The proposed model considers pseudo-steady state and charge carrier transfer processes.

Abstract

The photocatalytic activity as a function of effective irradiance, photocatalytic quantum yield and reactant coverage was thoroughly assessed for the proper photoreactor (PhR) selection. The emitted wavelength and effective irradiance of several PhRs, equipped with fluorescent and light-emitting diode (LED) lamps, were tested in the photodegradation of methylene blue (MB) in the solid phase using an AgTiO2 photocatalyst. Among all tested PhRs, the one equipped with the low-pressure Hg lamp enhanced the photodegradation of MB, as the Hg lamp emitted UV-type radiation, which promotes the simultaneous photoactivation of the TiO2 and the surface plasmon resonance phenomenon of the Ag nanoparticles. It was determined that high values of effective irradiance promoted photocatalytic activity because of the greater amount of photogenerated species [e−/h+]. Also, it was determined that the effective irradiance used in the photocatalytic process slows down the recombination rate of the [e−/h+] into photocatalytic material. A kinetic photocatalytic model (KPM) was proposed to describe photocatalytic reactions as a function of effective irradiance, photocatalytic quantum yield and reactant coverage, considering photocatalytic pseudo-steady state according to the reactant equilibrium coverage (Langmuir isotherm) and the transfer processes of the photoinduced charge carrier species.

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