| Summary: | The synthesis of Fe3O4/SiO2 modified with N-(2-aminoethyl)-3-
aminopropyl group (Fe3O4/SiO2/ED) and investigation Au(III) recovery in the
multimetal system Au(III)/Cu(II)/Cr(VI) have been conducted. Fe3O4/SiO2/ED
was synthesized via Stöber�s modifications method with methanol as dispersant of
magnetite. Precursor sodium silicate and N-(2-aminoethyl)-3-aminopropyl
trimethoxy silane (EDS) was added as aminosilica shell shaper. The synthesized
samples were characterized by X-ray diffraction (XRD), Fourier transform
infrared (FT-IR) spectrophotometer and transmission electron microscopy (TEM).
Experimental parameter affecting Au(III) adsorption onto Fe3O4/SiO2/ED such as
pH, contact time, initial concentration were studied. Study of kinetic data was
analyzed using first-order, second-order, pseudo-first-order and pseudo-second
order. Furthermore, the Langmuir and Freundlich isotherm models were used to
determine it�s capacity and adsorption energy. Desorption by thiourea-HCl 2%
and the reusability of adsorbents were done by adsorption-desorption cycle.
The characterization with XRD, FT-IR and TEM proved that SiO2 and N-
(2-aminoethyl)-3-aminopropyl group was successfully covered the magnetite
particle to form Fe3O4/SiO2/ED adsorbent. Study of kinetic data showed that the
adsorption of Au(III) on Fe3O4/SiO2/EDS fits to pseudo-second order model with
rate constant of adsorption is 0.710 g mmol L-1min-1. The best interpretation for
the experimental data was given by Langmuir isotherm model. The maximum
adsorption capacity for Au(III) is 142.85 mg/g and the energy of adsorption is
25,052 kJ/mol. Gold loaded on the adsorbent could be easily desorbed by 0,2
mol/L HCl containing 2% of thiourea with 99,82% efficiency. The reusability
Fe3O4/SiO2/ED shows the high stability of the adsorbent within 5 times
adsorption-desorption cycle with more than 90% efficiency. Adsorbent also shows
selectivity in adsorbing Au(III) in the multimetal system Au(III)/Cu(II)/Cr(VI)
with the coefficient selectivity �Au-Cu (227.473) and �Au-Cr (12.261).
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