Effect of adsorbate polarity on thermodesorption profiles from oxidized and metal-impregnated activated carbons Original Research Article

Oxidation and impregnation treatments of activated carbons result in sorbents with selected properties and reduced surface areas. In this work, to investigate the effects of these methods on both the porous structure and surface chemistry, activated carbons derived from peach stones were oxidized with concentrated nitric acid and then impregnated with inorganic salts of iron and copper. The changes caused by the oxidative and impregnation treatments were characterized by elemental analysis, nitrogen adsorption isotherms, thermal analysis, and thermodesorption studies. It was found that oxidation and wet impregnation resulted in a decrease of the surface area of the activated carbons, due to partial or complete pore blockage with oxygen complexes and/or adsorbed species. The thermal behavior of unmodified and chemically modified activated carbons was investigated by thermogravimetric analysis (TGA) and it was observed that all the treatments lead to higher weight losses. Thermogravimetry studies were used to characterize the thermodesorption of water, n-butanol, and n-heptane and the effect of adsorbate polarity on the thermodesorption profiles from oxidized and metal-impregnated activated carbons. The thermogravimetric studies show that the temperature domain in which desorption occurs depends on the interaction between the adsorbate molecules and the carbon surface.