Formation of hydroxyl radical mediated by oxygenation of reduced Fe-bearing aluminosilicate clay minerals: Implications for straw degradation

Three clay minerals (i.e., chlorite, montmorillonite and attapulgite) were selected with the exploration of the formation and mechanisms of HO• and its influences on straw degradation by incubation experiment, Fe K-edge X-ray absorption near edge structure spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy, etc. The formation of HO• was mainly regulated by oxygen vacancies of minerals which determined the peroxidase-like activity and electron transportation rate between Fe(II) and O2, rather than by the content and form of Fe(II). The Raman spectroscopy results showed that the intensity of β-folded conformation within the mineral in this incubation system which represents cellulose degradation products increased as compared to the raw mineral, providing direct evidence for the straw degradation. Montmorillonite was more favorable for HO• formation and the related straw degradation.