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Abstract
Mass transfer behavior of ion exchange of both Nt2 and Cd+2 ion has been studied using batch gas sparged vessel in relation to the following parameters
Variables studied were (1) physical properties of the solution (p, ~, D), (2) superficial gas velocity,(3) initial concentration of the heavy metal,(4) temperature (5) amounl of resin.
The study revealed the following results for Ni+2 ions:
(1) First order kinetic model best described the kinetic data for Ni+2 ion exchange a1 low concentration rang (50 - 100 ppm), where film diffusion is controlled and the first order rate constant increased as the gas superficial velocity increased accordin~ to the following equation:
Also first order rate constant increased with increasing temperature and amount 0: resin.
However, with increasing the initial Ni+2 concentrations, the first order rate constan’ decreased.
(2) The kinetic data were correlated using dimensionless analysis for the conditions: 365 Sc 501
1.7 Re.Fr 2.87
by the following equation:
Jo = 0.17 (Re. Frro.13
(3) Pseudo second order kinetic model best described the kinetic data for Nt2 io: exchange at concentration rang (150 - 250 ppm).
In which both film diffusion and intra-particle diffusion are contributing in the rate c ion exchange. The second order rate constant increased as superficial gas velocit increases also it increased as Ni+2 initial concentration decreased.
The study also revealed the following results for Cd+2 ions:
(l) First order kinetic model best described the kinetic data for Cd+2 ion exchange; concentration rang (50 - 200 ppm), where both film and intraparticle diffusion controlled and the first order rate constant increased as the gas superficial veloci’ increased according to the following equation:
Also first order rate constant increased with increasing temperature and amount resin.
by the following equation:
JD = O. I 8 (Re. Fr)-o•15
(3) Pseudo second order kinetic model best described the kinetic data for Cd+2 ion exchange at concentration (50 - 200 ppm).
In which both film diffusion and intra-particle diffusion are contributing in the rate of ion exchange. The second order rate constant increased as superficial gas velocity, temperature and amount of resin increases also it increased as Cd+2 initial concentration decreased.
Comparative study between ion exchange of Ni+2 and ion exchange of Cd+2 revealed the following:
(I) Intraparticle diffusion is predominant in Cd+2 ion exchange case than in Ni+2 case. (2) Activation energy calculation revealed that both reactions are diffusion controlled with average activation energies 5 kcal/mol and 7 kcal/mol for Nt2 and Cd+2 respectively.
(3) Thermodynamic functions calculations showed that the ion exchange reaction of both heavy metals is endothermic reaction.
The presence of Cd+2 with Ni+2 could effect the ion exchange removal of Nt2 especially at low gas velocity, as the concentration of Cd+2 increased, % Nt2 removal decreased.