In this study, a green adsorbent was successfully applied to remove toxic metals from aqueous solutions.
Dried minced castor leaves were fractionated into 63-m particles to perform characterization
and extraction experiments. Absorption bands in FTIR (Fourier Transform Infrared Spectroscopy) spectra
at 1544, 1232 and 1350 cm−1 were assigned to nitrogen-containing groups. Elemental analysis showed
high nitrogen and sulfur content: 5.76 and 1.93%, respectively. The adsorption kinetics for Cd(II) and Pb(II)
followed a pseudo-second-order model, and no difference between the experimental and calculated Nf
values (0.094 and 0.05 mmol g−1 for Cd(II) and Pb(II), respectively) was observed. The Ns values calculated
using the modified Langmuir equation, 0.340 and 0.327 mmol g−1 for Cd(II) and Pb(II), respectively,
were superior to the results obtained for several materials in the literature. The method proposed in this
study was applied to pre-concentrate (45-fold enrichment factor) and used to measure Cd(II) and Pb(II)
in freshwater samples from the Paraná River. The method was validated through a comparative analysis
with a standard reference material (1643e).