SORPTION-DESORPTION MECHANISM OF Zn(II) AND Cd(II) ON CHITIN
ABSTRACT: This study reports
the results of the elucidation of the sorption-desorption mechanism of Zn(II)
and Cd(II) on chitin through the determination of capacity, energy, and rate
constant of sorption as well as the investigation of their desorption
properties in NaCl and Na 2 EDTA solutions. The chitin was isolated through
deproteination followed by demineralization of crab (Portunus pelagicus Linn)
shell using NaOH solutions. The sorption of both metal ions followed the
Langmuir isotherm model, resulting the sorption capacities of 3.2 x 10 -4 and
2.8 x 10 -4 mol g -1 for Zn(II) and Cd(II), respectively, and sorption energies
of 15.1 kJ mol -1 for Zn(II) and 17.9 kJ mol -1 for Cd(II). It was also observed
that Zn(II) was sorbed slightly faster than Cd(II) with first order sorption
rate constants of 2.82 x 10 -3 min -1 for Zn(II) and 2.61 x 10 -3 min -1 for
Cd(II). The result of the desorption experiment showed that Cd(II) and
especially Zn(II) could only be exchanged by Na(I) after desorbing those metal
ions by strong chelating agent of EDTA 2- . The easier desorption of Zn(II)
than Cd(II) by EDTA 2- must be attributed by the smaller sorption energy of
Zn(II) and by harder acid property of Zn(II) than Cd(II) as EDTA 2- contained
hard electron donor elements.
Author: Sri Juari Santosa,
Narsit , and Aldes Lesbani
Journal Code: jpkimiagg060012
