Mass transfer studies of the adsorption of dialysates from artificial kidney by activated carbon

Abstract

The mass transfer characteristics on the adsorption of dialysates by activated carbon was investigated. Experimental data show that the isotherm of urea in linear and those of creatinine and uricacid are of Langmuir type. A 1000 gr. bed of carbon has equilibrium capacities for only 5.5gr. of urea, for 20gr. of creatinine and uric acid respectively. thus, adsorption of creatinine and uric acid by activated carbon was effective but the adsorption of urea was not. The equilibrium adsorption capacity of carbon for these adsorbates decreases when the temperature is raised. The external diffusion coefficient varied as the 0.16 power of the velocity and inversely as the 0.58 power of the particle diameter and represented for the Urim-Charcoal (Seoul, Korea) as follows. $$K_s\;\alpha(V)^{0.16}(dp)^{-0.58}$ Effectiveness factor for activated carbon particles (18-30 mesh sizes) was studied and decreased when the particle size becomes larger. This means that the larger particles are more strongly affected by the intraparticle resistances. It was shown that external and internal diffusional resistance are significant in the present study. Overall membrane resistance is determined by a duel closed - loop technique with which the effects of blood flow rate, dialysate flow rate on the overall membrane resistance is examined. The increase of blood flow rate and dialysate flow rate decreases overall membrane resistance due to the reduction of film resistance. The kinetics of metabolic wastes (creatinine) by hemodialyzer with packed column was simulated. The results from simulation show that the metabolites can be removed effectively with the packed column of activated carbon.