By comparing the correlation coefficients, it is found that the
pseudo-first-order model is unable to fit the experiment data,
while the pseudo-second-order model can give a well description
of the kinetic behavior (R2 > 0.999 for all cases), suggesting that
the rate-limiting factor may be chemical adsorption involving
valence forces through sharing or exchange of electrons between
adsorbent and adsorbate as covalent forces [30]. Azizian [31]
proved theoretically that if the initial concentration of solute is
high for the amount of active sites, then the pseudo-first-order