Influence of surface properties of carbon black on the activity of adsorbed catalase

Homologous series of carbon samples were prepared from a non-porous thermal carbon black by oxidation with various concentrations of hydrogen peroxide at 95 degrees C. The samples were characterized by X-ray photoelectron spectroscopy, gas adsorption, and electrophoretic mobility measurement; the enzymatic activity of catalase adsorbed on the carbons blacks was also examined. No significant variation of texture was produced by oxidation. The oxygen surface concentration increased as a function of the H2O2 concentration up to 0.8 M, and tended to decrease above this concentration; this is attributed to the competition between surface modification and release of products of oxidation. The surface was found to be more negative as the oxygen concentration increased. The specific activity of catalase adsorbed (degree of coverage about 0.5%) on non-oxidized carbon is much lower that the specific activity of dissolved catalase, indicating a modification of the enzyme conformation in the adsorbed slate. The activity increases with the oxygen surface concentration; this is attributed to a weaker interaction with the surface, due to its lower hydrophobicity, or a stronger contribution of electrostatic repulsion. Catalase activity measurements appear as a promising way to probe carbon surface properties.