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Chromate removal as influenced by the structural changes of soil components upon carbonization at different temperatures

Chen, K.Y., Liu, J.C., Chiang, P.N., Wang, S.L., Kuan, W.H., Tzou, Y.M., Deng, Y., Tseng, K.J., Chen, C.C., Wang, M.K.
Environmental pollution 2012 v.162 pp. 151-158
Fourier transform infrared spectroscopy, air, carbon, carbonization, chromium, heat, nuclear magnetic resonance spectroscopy, potassium chloride, soil organic matter, temperature
Surface fire could induce heat transferring into the soil, creating a carbonized environment, which may alter the chemical compositions of soil organic matters (SOM). In the study, a surface soil was carbonized at up to 600 °C with limited air to simulate soils experiencing a surface fire, and Cr(VI) removal on the carbonized soils was investigated. NMR and FTIR analyses demonstrated a remarkable change of SOM structures at 300–400 °C. TGA-MS spectra indicated that (e.g. C₂H₄, CH₃OH and C₃H₈) were the major components in the evolved gases from the pyrolyzed soil. A maximum amount of Cr(VI) removal (ca. 4 mg g⁻¹ soil) occurred for the 200 °C-carbonized soils, attributed mainly to a significant increase of Cr(VI) reduction by 0.1 M KCl extractable organic carbon (EOC) with abundant carboxylic groups. Nonetheless, the formation of aromatic C upon carbonization of the soil at >400 °C may be responsible for Cr(VI) reduction.