INFLUENCE OF SURFACE-PROPERTIES OF CARBON-BLACK ON THE ACTIVITY OF ADSORBED CATALASE

Homologous series of carbon samples were prepared from a non-porous th ermal carbon black by oxidation with various concentrations of hydroge n peroxide at 95 degrees C. The samples were characterized by X-ray ph otoelectron spectroscopy, gas adsorption, and electrophoretic mobility measurement; the enzymatic activity of catalase adsorbed on the carbo ns blacks was also examined. No significant variation of texture was p roduced 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 betwe en surface modification and release of products of oxidation. The surf ace was found to be more negative as the oxygen concentration increase d. The specific activity of catalase adsorbed (degree of coverage abou t 0.5%) on non-oxidized carbon is much lower that the specific activit y of dissolved catalase, indicating a modification of the enzyme confo rmation 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 contribut ion of electrostatic repulsion. Catalase activity measurements appear as a promising way to probe carbon surface properties.