Four types of soil clays from different sites in China have been chosen to simulate chemical remediation of soils contaminated with dyes by light-assisted Fenton-like method. X-Ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS) and electron spin resonance (ESR) measurements indicated that these soil clays contain iron oxides such as magnetite and hematite, where nondistorted iron active sites (ESR spectra, g = 2.3) predominate. Upon visible or UV irradiation, the soil clays were very effective for the degradation of nonbiodegradable cationic dyes such as Rhodamine B (RhB) by activating H2O2 at neutral pH. The photodegradation rates of RhB were closely related to total Fe content in clays and H2O2 dosage, indicating the mineral-catalyzed Fenton-like reactions operated. Soil organic matters (SOM) would remarkably inhibit the photodecomposition of RhB dye. The reaction products were some low-molecular-weight dicarboxylic acids and their derivatives, all of which are easily biodegradable. A possible mechanism was proposed based on the results obtained by spin-trapping ESR technique.
Wang, Z, Ma, W, Chen, C & Zhao, J 2009, 'Light-assisted decomposition of dyes over iron-bearing soil clays in the presence of H2O2', Journal of Hazardous Materials, vol. 168, no. 2-3, pp. 1246-1252.
Published version available from: http://dx.doi.org/10.1016/j.jhazmat.2009.02.160