4. Conclusions
In this study, the removal of copper, cadmium and lead
metal ions from aqueous solution by adsorption on olivestone
activated carbon produced by thermo chemical
process using phosphoric acid (COSAC) was investigated.
The obtained results show that metal adsorption is pH-
dependent and maximum adsorption was found to occur at
an initial pH of 5.0. The adsorption equilibrium was fast and
was achieved, in our experimental conditions, after 200 min
for the three metal ions studied. The kinetics of metal
adsorption on COSAC follows the pseudo-second-order rate
model and calculated initial rate constants (h) and external
mass transfer coefficients (kL) follow the order: Pb(II) > CCd(
II) > Cu(II). The equilibrium adsorption data are best fitted
by the Redlich–Peterson model as compared to Langmuir,
Freundlich and Sips models, and the adsorption capacity of
COSAC decreased in the order: Pb(II) (147.526 mg/g) > Cd(II)
(57.098 mg/g) > Cu(II) (17.665 mg/g).
Our binary adsorption study evidences that the affinity
of copper toward the carbon surface is stronger than that of
nickel or lead. The examination of binary adsorption
systems Cu–Cd and Cu–Pb shows that the affinity of copper
toward prepared activated carbon surfaces was strongly
dependent on the initial concentration of nickel and lead.
The adsorption amount of copper increased in the presence
of nickel and decreased in the presence of lead.
The results evidence that COSAC is a promising material
for metal ions elimination in single and binary mixtures, due
to its high specific surface area and to the presence of
specific oxygen functional groups such as carbonyl, phenol
and carboxylic ones, responsible for heavy metal ion uptake.
.