From Table II, the R2 value for the

From Table II, the R2 value for the pseudo-second-order
model was higher than the pseudo-first-order model. This
showed that the adsorption of copper on chicken eggshells
was well-fitted to the pseudo-second-order kinetics model
compared to the first-order model. It can be concluded that the
pseudo-second-order kinetics model provides a good
correlation for the adsorption of Cu(II) on chicken eggshells
and it also suggests that the chemisorption process could be
the rate-limiting step in the adsorption process. Similar
conclusion was also reported for the adsorption of heavy metal
ions by other adsorbents such as modified groundnut husks,
oil palm fibres, waste tea leaves and tree leaves waste [12].