Fe-Doped TiO₂-Carbonized Medium-Density Fiberboard for Photodegradation of Methylene Blue under Visible Light

Fe-doped titanium dioxide-carbonized medium-density fiberboard (Fe/TiO₂-cMDF) was evaluated for the photodegradation of methylene blue (MB) under a Blue (450 nm) light emitting diode (LED) module (6 W) and commercial LED (450 nm + 570 nm) bulbs (8 W, 12 W). Adsorption under daylight/dark conditions (three cycles each) and photodegradation (five cycles) were separately conducted. Photodegradation under Blue LED followed pseudo-second-order kinetics while photodegradation under commercial LED bulbs followed pseudo-first-order kinetics. Photodegradation rate constants were corrected by subtracting the adsorption rate constant except on the Blue LED experiment due to their difference in kinetics. For 8 W LED, the rate constants remained consistent at ~11.0 × 10^-3/h. For 12 W LED, the rate constant for the first cycle was found to have the fastest photodegradation performance at 41.4 × 10^-3/h. After the first cycle, the rate constants for the second to fifth cycle remained consistent at ~28.5 × 10^-3/h. The energy supplied by Blue LED or commercial LEDs was sufficient for the bandgap energy requirement of Fe/TiO₂-cMDF at 2.60 eV. Consequently, Fe/TiO₂-cMDF was considered as a potential wood-based composite for the continuous treatment of dye wastewater under visible light.