The pseudo-second-order kinetic model is analyzed by Ho and
McKay [21] based on the adsorption capacity and is expressed as
follows:
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where k2 is the equilibrium rate constant of pseudo-second-order
adsorption, mgg−1 min−1 and qe is the equilibrium adsorption
capacity, mgg−1. When the effect of initial concentration of both
single (RB21, RR195) and binary solution (RB21with RR195, RR195
with RB21) were compared, it was observed that k1 and k2 values
decrease with increasing initial concentrations. As shown in
Table 4, the values of correlation coefficients of the rate constant of
pseudo-first-order are less than R2 < 0.980. As a result, the models
which provided the best correlation with experimental data were
the pseudo-second-order model.