The parameters with greater influence in the adsorption
properties of the activated carbons are the precursor nature, the
activation temperature, and the impregnation ratio. Aguaje stones
offer a promising raw material for the production of activated
carbon for water treatment purposes.
The activated carbon chemical and textural characteristics are
highly related to the precursor nature and generate different
adsorption capacities, although both precursors (aguaje and olive
fruit stones) were prepared under the same conditions.
The activated carbons with the highest adsorption capacities
were: from AG series, AG0.75_600 (26.33 mg g1
) and from OL
series OL1_600 (24.83 mg g1
) at pH 5. Both activated carbons
presented a high developed mesoporous area (140 y 125 m2 g1
,
respectively) and a high superficial acidity (2.43 y 2.37 mmol
H+ g1
, respectively). The high lignin content and natural fiber
compaction in olive stones required a higher impregnation ratio to
get a suitable superficial acidity and mesoporous area to increase
the cadmium ion adsorption.
The kinetic curve fitted suitably to pseudo second order model,
which allows to establish that the adsorption process is the result
of two types of interactions, chemical and physical, between the
metal ion and the activated carbon surface.
The isotherm model fits suitably to Langmuir model. In
accordance with Redlich–Peterson’s G parameter near to 1, the
adsorption process mostly takes place in homogeneous active sites
over the activated carbon surface.
Co