The results obtained in the present work demonstrate that the
pecan shells (C. illinoinensis) contains calcium compounds which
favor the biosorption of anionic dyes. Accordingly, the biosorption
mechanism is influenced by the number of suphonic groups
presents in the dye molecules which are thought to interact with
the calcium present in pecan shells. Modeling of the biosorption
results indicated that the pseudo-second order model offers a better
correlation of experimental kinetic data and both Langmuir
and Sips models are a suitable option for modeling the sorption
isotherms of AB25, RB4 and AB74 on pecan shells. Finally, the
results show that pecan shells have a very limited performance
in dye removal processes using dynamic adsorption configurations
(packed-bed columns). Alternatively, batch mode operation should
be preferred for these biosorbent.