engleski

The rate controlling step in competitive binding of Pb, Cd and Zn from binary systems onto fixed zeolite bed

The rate controlling step in the fixed bed has been qualitatively evaluated by the graphical method and quantitatively determined by calculation of the overall mass transfer coefficient, for binary systems (Pb+Zn) and (Cd+Zn). The overall mass transfer is higher in the (Cd+Zn) system compared to the (Pb+Zn) one for the same experimental conditions. The reason for this is much less pronounced competition between Cd and Zn ions in the (Cd+Zn) binary system compared to Pb and Zn in the (Pb+Zn) binary system, due to similar physical properties of Cd and Zn ions. By increasing the flow rate the increase in the overall mass transfer coefficient has been obtained due to shorter contact time between the solute and zeolite. The mass transfer of Zn ions increases with decreasing Cd or Pb concentrations in the influent, as well as with increased flow rate, since all this contributes to reducing the competition effect.

lead, zinc, cadmium, binary systems, zeolite fixed bed, rate controlling step

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