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For the purpose of clay examination, a new one-step method for the removal of organic matter was developed using sodium peroxodisulphate combined with different buffers such as sodium hydrogen carbonate, disodium hydrogen phosphate and disodium tetraborate. From an early Cretaceous black shale from the Apennines with a high organic carbon content, the <2 gm clay fraction was separated and contained 10.9 wt% organic carbon. To prevent decomposition of the clay layers, the period of oxidation was short (25-60 min) and the pH was kept between 5 and 9.5. Up to 98% of carbon was removed by this method.

The use of disodium peroxodisulphate combined with a neutral buffer is a new method for the efficient removal of organic matter from clay-bearing sediments. The effects of this oxidation procedure on mineral structure were investigated by treatment of different standard clay minerals (kaolinite ‘china clay’, illite ‘Le Puy’, montmorillonite SWy-1). The materials were characterized by means of XRD, FTIR, SEM and TEM before and after leaching with disodium peroxodisulphate. Systematic experiments were conducted to determine the effects of leaching on the chemical and isotopic composition of oxygen, hydrogen and K-Ar in these samples. Effects on the physicochemical properties of the clays such as BET external surface area, cation exchange capacity (CEC) and expandability with ethylene glycol were also investigated. The results show that structure, chemical composition, oxygen and hydrogen isotope ratios, as well as the K-Ar system remain unaffected by leaching with disodium peroxodisulphate. The CEC and expandability remain unchanged, whereas changes in BET area can be attributed to mechanical dispersion by ultrasonic treatment.