Removal of organic matter by disodium peroxodisulphate: effects on mineralstructure, chemical composition and physicochemical properties of some clay minerals

The use of disodium peroxodisulphate combined with a neutral buffer is a ne w method for the efficient removal of organic matter from clay-bearing sedi ments. The effects of this oxidation procedure on mineral structure were in vestigated by treatment of different standard clay minerals (kaolinite 'chi na clay', illite 'Le Puy', montmorillonite SWy-1). The materials were chara cterized by means of XRD, FTIR, SEM and TEM before and after leaching with disodium peroxodisulphate. Systematic experiments were conducted to determi ne the effects of leaching on the chemical and isotopic composition of oxyg en, hydrogen and K-Ar in these samples. Effects on the physicochemical prop erties of the clays such as BET external surface area, cation exchange capa city (CEC) and expandability with ethylene glycol were also investigated. T he results show that structure, chemical composition, oxygen and hydrogen i sotope ratios, as well as the K-Ar system remain unaffected by leaching wit h disodium peroxodisulphate. The CEC and expandability remain unchanged, wh ereas changes in BET area can be attributed to mechanical dispersion by ult rasonic treatment.