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Arab Journal Of Nuclear Science And Applications, 46(2),(1-16) 2013
ii. Pseudo-second-order:
A pseudo-second-order rate model is used to describe the kinetics of the sorption of metal ions
onto sorbent materials (15,16,17) . The second model used to describe the kinetics of the adsorption of
Sr +3 , Co +2 , Cd +2 , Zn +2 , Nd +3 and Eu 3+ by poly-acrylic acid/2-Hydroxyethylmethacrylate (P-
AAc/HEMA) at different temperatures is pseudo second-order model, which presented in equation
(3).
t 1 1
t
(3)
q k q q
2
2 e e
Where, k2 is the pseudo second-order rate constant. The qe and k2 values of the pseudosecond-order
kinetic model can be determined from the slope and the intercept of the plots of t/q
versus t, respectively. Figs. (12-1) : (12-6) give the results of the linearized form of the pseudosecond-order
kinetic model. The calculated qe values are more closer to the experimental data than the
calculated values of pseudo-first-order model. Therefore, the sorption of the six ions can be
approximated more favorably by the pseudo-second-order model, Table (4) illustrates that the
correlation coefficients are very high, R 2 >0.99, for pseudo-second-order kinetic model this
reinforcing the applicability of this model.
Table (4) The kinetic parameters of Pseudo-second-order model for sorption of Sr 2+ , Nd 3+ , Eu 3+
,Co 2+ ,Cd 2+ and Zn 2+ onto P-AAc/HEMA at different temperatures.
Temp,
o K
k2
,g/mmol
.min
Sr Nd Eu
qe ,
calc.,
mmol/g
R 2
k2
,g/mmol
.min
12
qe ,
calc.,
mmol/g
R 2
k2
,g/mmol
.min
qe ,
calc.,
mmol/g
298 5.68 0.017065 0.999 5.96 0.016313 0.999 5.28 0.018797 0.997
303 7.22 0.018149 0.998 10.62 0.01642 0.999 7.77 0.01912 0.998
313 17.47 0.017637 0.999 16.96 0.016556 0.995 11.08 0.019231 0.999
323 28.25 0.017699 0.996 25.29 0.017241 0.999 17.49 0.019455 0.999
Temp,
o K
k2
,g/mmol
.min
Co Cd Zn
qe ,
calc.,
mmol/g
R 2
k2
,g/mmol
.min
qe ,
calc.,
mmol/g
R 2
k2
,g/mmol
.min
qe ,
calc.,
mmol/g
298 7.33 0.015576 0.999 8.05 0.01548 0.998 7.68 0.015748 0.999
303 9.81 0.015723 0.997 17.66 0.015552 0.999 14.271 0.015848 0.997
313 18.15 0.015823 0.999 19.6 0.016181 0.998 15.59 0.016807 0.998
323 42.2 0.015873 0.996 25.17 0.017153 0.999 27.81 0.016892 0.999
R 2
R 2