Abstract:
Mixed oxide of iron-silicon adsorbent was synthesized chemically by a sol-gel
method. Fe-Si binary oxide adsorbents were prepared by varying the
concentration of Fe(III) while the concentration of Na2CO3 and Na2SiO3 were kept
constant and also by varying the concentration of Na2CO3 while the concentration
of Fe(III) and Na2SiO3 was chosen to be constant. In this study Fe/Si molar ratio
and Na2CO3 concentration were selected to be 3:1 and 0.5 M respectively.
The mixed oxide thus obtained and characterized by a wide range of EDX, XRD,
SEM, UV-Visible and IR spectroscopy techniques. Elemental analysis exhibited
the presence of iron, silicon and oxygen elements in the mixed oxide with a
composition of Fe1.47 Si0.53 O3. The results showed that the iron-silicon mixed
oxide were successfully synthesized. The IR spectra yielded the characteristics
signals of silicon oxide (470, 1099 cm-1), iron oxide (457, 545, 569 cm-1) and
iron−silicon mixed oxide (962 cm-1) and confirmed the presence of the
components in each substrate. The average crystallite size was calculated from
the XRD data to be approximately 18 nm. The specific surface area of this binary
oxide was found to be 46.79 m2g-1. The point zero charge of this surface was
observed to be at pH 8.8.
Surface capacity of the mixed metal oxide (MMO) were studied and thus it was
used as an adsorbent for the removal of organic dyestuff from water. In that case,
organic cationic (methylene blue abbreviated as MB) and anionic (orange green
abbreviated as OG) dyes were attempted to be adsorbed on the MMO surface.
The adsorption data showed that both the MB and OG dyes can be adsorbed on
the mixed oxide surface. But the extent of MB adsorption is much more higher
than OG, suggesting the present MMO an attractive adsorbent for the removal of
the cationic dye MB.
The adsorption property of mixed oxide for removal of organic cationic MB dye
was investigated with various parameters including effect of pH, contact time,
initial dye concentration, temperature and dose of mixed oxide. The adsorbent
was tested for removal of dyes from their aqueous solution. The maximum
adsorption capacity of binary mixed (Fe-Si) oxide for MB dye was found at pH 7.
Kinetic study showed that MB followed pseudo-second-order kinetics equation for
MB. Adsorption isotherm was interpreted by Langmuir equation from the obtained data. This study clearly demonstrated that dye can be removed efficiently by the
Fe-Si mixed oxide surface.
