1984 Volume 10 Issue 4 Pages 461-468
From the measurement of equilibrium relations of three water-soluble organic compounds containing nitrogen, dicyandiamide (S1), melamine (S2) and p-phenylene diamine (S3), on active carbon, it was found that these adsorbates have the same order of magnitude of adsorbability as those of other organic adsorbates which have high adsorbabilities on active carbon.
The intraparticle distributions of accumulated average concentration, Qx, exp. were measured by the nitrogen-tracer method. The Qx, exp.-values were then compared with the Qx, calc.values calculated from diffusion equations, and on the basis of the above comparisons the adsorption and desorption rates as well as the intraparticle diffusion mechanisms were studied. 1) The shapes of the intraparticle distributions of accumulated average concentration showed close linkage to the diffusion mechanism assumed. For sample S2, simultaneous pore- and surface-diffusion dominate the rates. On the other hand, the adsorption rates of samples Si and S3 are controlled by surface diffusion alone. 2) The same diffusion mechanism is valid for both adsorption and desorption, and the surface diffusivity, Ds, of sample S1 for desorption has almost the same value as that for adsorption. For sample S2, the Ds-value for desorption is 0.1 to 0.3 times smaller than that in adsorption.