Surface and catalytic properties of gamma-irradiated CuO and NiO catalysts

The effects of gamma-irradiation (20-160 Mrad) on surface and catalytic properties of CuO and NiO were investigated. The surface characteristics namely S-BET, V-p, and (r) over bar of various solids were determined from nitrogen adsorption isotherms conducted at -196 degrees C and their catalytic activities were measured by following up the kinetics of CO-oxidation by O-2 using a static method, The results showed that gamma rays brought about a small increase (24%) in the S-BET of CuO till a dose of 40 Mrad, and a dose of 80 Mrad was found to increase considerably its S-BET (224%) due to narrowing of its pores ((r) over bar decreased from 110 to 61 Angstrom). In the case of NiO solid its S-BET was found to vary in a complex manner up on exposure to different doses of gamma-rays. Gamma rays modified the catalytic activity of CuO catalyst in a complex manner. The catalytic activity of NiO, being expressed as the reaction rate constant k, was found to decrease progressively by increasing the dose in the range 20-120 Mrad. However, the reaction rate constant per unit surface area ((k) over bar) of NiO decreased slightly (18%) by exposure to a dose of 20 Mrad. By increasing the dose to 40 Mrad a maximum specific catalytic activity ((k) over bar) was observed. The further increase of the dose to 80 Mrad resulted in a sudden drop (69%) in the specific catalytic activity ((k) over bar) of the treated solid. Irradiation at 120 Mrad brought about an increase (14%) in the value of (k) over bar.