Room-temperature synthesis and photocatalytic properties of lepidocrocite by monowavelength visible light irradiation

Lepidocrocite was synthesized by aerial oxidation using an Fell EDTA solution. The synthesis was performed under irradiation from different monowavelength light emitting diode (LED) lamps at room temperature. X-ray diffraction results showed the formation of differently crystallized lepidocrocite. The indirect bandgap values of the lepidocrocite samples were about 2.34, 2.36, and 2.31 eV for red, green, and blue light, respectively. The kinetics of the photo-decolorization of crystal violet (CV) was investigated in a system composed of lepidocrocite, H2O2, and visible light. H2O2 concentration, light irradiation, and catalyst concentration were also investigated. The rate of CV decolorization was found to fit pseudo-first-order kinetics. The results show that different as-prepared lepidocrocite have different adsorption and photocatalytic characteristics. A possible mechanism was also suggested for the dye degradation. (C) 2011 Elsevier B.V. All rights reserved.