There are many factors which can contribute to the
sorbate concentration effect. The first and important one is
that adsorption sites remain unsaturated during the
adsorption reaction. The second cause can be the
aggregation/agglomeration of sorbent particles at higher
concentrations. Such aggregation would lead to a decrease
in the total surface area of the sorbent particles available for
metal adsorption and an increase in the diffusional path
length. The particle interaction brought about at high
sorbent concentrations may also desorb some of the metal
ions, which are loosely and reversibly bound to the sorbent
surface