Characterization of Pequi (<i>Caryocar brasiliense</i>) Shells and Evaluation of Their Potential for the Adsorption of Pb<sup>II</sup>Ions in Aqueous Systems

Amorim, Dayane J.; Rezende, Hélen C.; Oliveira, Érica L.; Almeida, Ione L. S.; Coelho, Nívia M. M.; Matos, Túlio N.; Araújo, Cleide S. T.

doi:10.5935/0103-5053.20150304

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Articles • J. Braz. Chem. Soc. 27 (3) • Mar 2016 • https://doi.org/10.5935/0103-5053.20150304 copy

Characterization of Pequi (Caryocar brasiliense) Shells and Evaluation of Their Potential for the Adsorption of Pb^IIIons in Aqueous Systems

Authorship SCIMAGO INSTITUTIONS RANKINGS

In this study pequi (Caryocar brasiliense) shells were evaluated in relation to their potential for the adsorption of Pb^II ions in aqueous systems. The adsorbent was characterized by point of zero charge (PZC), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Pb^II ions were detected by flame atomic absorption spectrometry (FAAS). The adsorption parameters studied were solution pH, adsorbent mass, contact time and the optimum adsorption conditions were found to be 7.0, 50 mg and 30 min, respectively, using 15 mL of the metal solution. A study on the adsorption kinetics and isotherms was performed applying the optimized conditions. The adsorption process followed a pseudo-second-order model. The experimental adsorption data were fitted to the Langmuir and Freundlich isotherm adsorptions and a very good fit to the Langmuir linear model was observed. The maximum adsorption capacity was found to be 35.52 mg g^-1.

Keywords:
Pb^II adsorption; isotherm; kinetic of biosorption; pequi shell

Pseudo-first-order					Pseudo-second-order
k₁^a a k1: Pseudo-first-order rate constant; / min^-1	Q_e exp ^b b Qe exp: experimental biosorption capacity; / (mg g^-1)	Q_e cal ^c c Qe cal: biosorption capacity calculated; / (mg g^-1)	R²^d d R2: correlation coefficient;		k₂^e e k2: pseudo-second-order rate constant / (mg g^-1 min^-1)	Q_e exp ^b b Qe exp: experimental biosorption capacity; / (mg g^-1)	Q_e cal ^c c Qe cal: biosorption capacity calculated; / (mg g^-1)	R²^d d R2: correlation coefficient;
0.00921	0.92	12.11	0.484		0.053	12.68	12.66	0.999

Langmuir model					Freundlich model
Q₀^a a Q0: Amount of adsorbate that can be absorbed by a unit mass of the adsorbent; / (mg g^-1)	b ^b b b: Langmuir constant; / (L mg^-1)	R_L^c c RL: Langmuir equilibrium parameter;	R²^d d R2: correlation coefficient;		k_f^e e kF: constant related to the sorption capacity of the adsorbent;	n ^f f n: constant related to the sorption intensity.	R²^d d R2: correlation coefficient;
35.52	0.10	0.25	0.9971		3.49	1.71	0.9762

Adsorbent	Q₀^a a Q0: Amount of adsorbate that can be absorbed by a unit mass of the adsorbent / (mg g^-1)	Reference
Peanut shells	30	16
Cow bone (activated carbon)	32.1	37
Nanostructured cedar leaf ash	7.23	38
Moringa oleifera	34.6	39
Rice husk ash	12.61	40
Eichhornia crassipes	26.32	41
This Study	35.5	-

Sample	PbII initial / (mg L^-1)	PbII final / (mg L^-1)	Adsorption / %
Residue from experimental class	5.4	0.8	85.3

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Characterization of Pequi (Caryocar brasiliense) Shells and Evaluation of Their Potential for the Adsorption of PbIIIons in Aqueous Systems

Characterization of Pequi (Caryocar brasiliense) Shells and Evaluation of Their Potential for the Adsorption of Pb^IIIons in Aqueous Systems