Experimental and theoretical studies of sorption kinetics of the anthracycline antitumor antibiotic rubomycin on a carboxylic heterogeneous sorbent Bidisperse model of sorption kinetics

The present work is devoted to experimental and theoretical studies of the sorption kinetics of the anthracycline antitumor antibiotic rubomycin on a carboxylic heteroreticular sorbent, BDM-12. The dependence of sorption kinetic parameters on the radius of sorbent grains has been experimentally obtained. The comparison of experimental data with the predictions of both homogeneous and "shell-and-core" models demonstrates the impossibility of using these models for adequate description of the rubomycin sorption kinetics on the sorbent, BDM-12. We have proposed a theory using the bidisperse model of heterogeneous sorbent grain and "linear driving force" approximation. This approximation can be applied at 10(-3) < alpha = tauI/tauA < 1, x < 1 and gives the values of the degree of process completion with relative errors approximately (alpha x)2. Here tauI and tauA are the characteristic times required for diffusion penetration into the macro- and microspheres, respectively, x is the ratio of the microsphere and macrosphere uptakes at equilibrium. The dependences of two characteristic times of the sorption process (for short- and long-time regions) on the radius of a sorbent grain have been derived. The predictions of the theory developed here are in good agreement with our experimental data and make it possible to calculate the kinetic parameters tauI, tauA and x.