SPECTROSCOPIC STUDY OF OXYGEN SORPTION AND DIFFUSION IN A MEMBRANE CONTAINING A COBALT PORPHYRIN COMPLEX.

The kinetics and equilibrium of molecular oxygen sorption in the membrane containing left bracket alpha , alpha prime , alpha double prime , alpha triple prime -meso-tetrakis(o-pivalamidophenyl) porphinato right bracket cobalt(II)-1-methylimidazole (CoPIm) complex which forms oxygen adduct rapidly and reversibly are studied spectroscopically. Oxygen sorption in the membrane containing the complex is interpreted in terms of dual mode sorption, whereby the sorbed oxygen exists as two populations: one sorbed to a polymer matrix according to Henry's law and the other to the fixed complex according to the Langmuir isotherm. The diffusion of oxygen in the membrane is found to be Fickian. Apparent oxygen diffusivity increases with an increase in the upstream oxygen pressure, which is in accordance with the dual mode transport model.