Plasma-surface modification vs air oxidation on carbon obtained from peach stone: Textural and chemical changes and the efficiency as adsorbents

Abstract

Carbons were prepared from peach stones (Prunus persica) using different carbonization temperatures (600, 800 and 1000°C). A selected sample was modified by oxidation using conventional oxidation techniques (thermal treatment in air atmosphere) and with cold oxygen plasma oxidation, under different conditions. Samples were characterized using elemental analysis, FT-IR spectroscopy, nitrogen adsorption isotherms at −196°C, SEM/EDX analysis, potentiometric titration and XPS analysis. Carbons with and without oxidation were employed in the adsorption of Pb2+ in aqueous solution. Results obtained indicated that the materials with high contents of acidic oxygen groups were more efficient in the removal of Pb2+, values as high as approx. 40mgg−1 being obtained for the best performing carbon. Textural properties of the original, un-oxidized carbon were significantly altered only after oxidation under air atmosphere at 450°C. On the other hand, the samples oxidized with plasma show little changes in the textural parameters and a slight increase in the specific surface was observed for the sample treated at high RF power (100W). Additionally, a significant increment of the oxygen content was observed for the plasma oxidized samples, as measured by XPS.