3.3. Optimization of functionalized SBA-15 amount
In order to consider the optimum amount of functionalized
SBA-15 for maximum take up of Pb2+, Cu2+, Zn2+ and Cd2+ ions,
the extraction was conducted by varying amounts of the functionalized
SBA-15 from 5–20 mg. Fig. 2b shows the obtaining results.
As it is seen, Pb2+, Cu2+, Zn2+ and Cd2+ can be extracted quantitatively
using 10 mg of functionalized SBA-15. Therefore subsequent
extraction experiments were carried out with 10 mg of functionalized
SBA-15.
3.4. The effect of the extraction time on extraction yield
The effect of the extraction time on the efficiency of the
extraction for a series of solutions containing 50 lg of Pb2+, Cu2+,
Zn2+ and Cd2+ ions was investigated and the results are depicted
in Fig. 2c. As it is seen, these ions can be extracted quantitatively
by the functionalized SBA-15 in the stirring time of 10 min and
more than it. Thus, the mixtures were stirred for 10 min in all of
the experiments.
3.5. The effect of the volume of acid on the stripping of Pb2+, Cu2+, Zn2+
and Cd2+
Some experiments were carried out in order to choose a proper
volume of nitric acid for the recovery of Pb2+, Cu2+, Zn2+ and Cd2+
ions after extraction by the functionalized SBA-15. The ions were
stripped with varying volumes of acid. Results showed (Fig. 2d)
that, 25 mL of 3.0 mol L1 nitric acid solution can accomplish the
quantitative elution of Pb2+, Cu2+, Zn2+ and Cd2+ ions from the
functionalized SBA-15.
3.6. Break through volume determination
The break through volume of the sample solution was studied
by dissolving 50 lg of the Pb2+, Cu2+, Zn2+ and Cd2+ ions in 250,
500, 1000, 2000 and 2500 mL of water, and the recommended procedure
was followed. In all cases, the extraction by functionalized
SBA-15 was found to be quantitative. Thus the break-through volume
for the method should be greater than 2500 mL. As recovery
of Pb2+, Cu2+, Zn2+ and Cd2+ ions was done with 25 mL nitric acid,
thus, preconcentration factor is 100.
3.7. Capacity of the functionalized SBA-15
The maximum capacity of functionalized SBA-15 was
determined by adding adsorbent to 25 mL portions of an aqueous
solution containing 10 mg Pb2+, 10mg Cu2+, 10mg Zn2+ and
10 mg Cd2+ and stirring it for 10 min and passing the resulting mixture
through a paper filter, followed by determination of the retained
metal ions using FAAS. The maximum capacity was found
to be 89.1 (±1.7) lg, 57.2 (±1.6) lg, 26.8 (±1.6) lg and 36.0
(±0.6) lg of Pb2+, Cu2+, Zn2+ and Cd2+ per mg functionalized
SBA-15, respectively.
3.8. Extraction and determination of Pb2+, Cu2+, Zn2+ and Cd2+ ions in
mixtures
In order to investigate the extraction of Pb2+, Cu2+, Zn2+ and Cd2+
ions from water solutions containing diverse metal ions, an aliquot
of aqueous solution (50 mL) containing 100 lg of Pb2+, Cu2+, Zn2+