A pseudo first order rate model for the adsorption of an organic adsorbatein aqueous solution

Five low rank, coal-based adsorbents, i.e. coal, grus, two chars, and an ac tivated carbon were used to adsorb a low molecular weight organic compound from aqueous solution. The rates of adsorption were found to conform to pse udo first order kinetics with good correlation (r(2) greater than 0.996). T his kinetic model was used to calculate pseudo first order rate constants ( k(1)' min(-1)) and relative rate constants (rate constant/unit mass of adso rbent, k(1)" min(-1) g(-1)) for the adsorption process. Rate properties hav e been explained in terms of both a diffusion and chemically controlled rat e determining step. Rate constants for the five adsorbents vary as expected on the basis of their physical properties, that is slowest for grus (compr essed coal) and fastest for the activated carbon. (C) 1999 Society of Chemi cal Industry.