| dc.description.abstract | Two natural occurring materials were investigated to test their efficacy in the removal of methylene
blue dye from an aqueous solution: A natural marine plant material (Carteriospongia Foliascens),
which is locally available and abundant in Coast and Lake Victoria and (Telfairia pedata) found in
Meru. The effect of equilibration time, ionic strength, adsorbate concentration, adsorbent loadings
and pH were investigated. For Carteriospongia Foliascens, fifteen minute's equilibration time was
found to be adequate and yielded 72% adsorption with a dye concentration of 2.5x 1a-sM.
Instantaneous adsorption of the dye was achieved at values higher than 66%. The surface material
was saturated and this was indicated by monolayer coverage adsorption after the conformity of the
data with the Langmuir isotherm. The % adsorption was found to increase with material weight due
to the increase of the available active sites for adsorption as well as with concentration of the dye.
The ionic strength of the solution had no effect on % adsorption. The isotherm studies were carried
out and both Langmuir and Freundlich models were applicable: The non-linearlised Freundlich
isotherms for the establishment of the existence of multilayer sorption and the linearlized Langmuir
isotherm to confirm the existence of monolayer coverage.
Similar studies were carried out using Telfairia Pedata and the results were quite similar as to the
above but for effect of KCI, where there was a decrease in% adsorption with increase in ionic
strength. The pH of the solution mixtures were found to increase with time. % Adsorption increased
with the pH, at lower pH, there was higher concentration of hydrogen ions hence possible
competition for the adsorption sites with the positive dye moiety, thus reduced adsorption. With
higher pH, there was low concentration of hydrogen ions in the solution; hence the dye molecules
received no competition thus exhibited higher % adsorption. 25minutes equilibration time was found
to be adequate with a % adsorption of 96. There was a subsequent adsorption of above 95% with a
dye concentration of 2.5x 1a-5M. The % adsorption showed a minimal increase with increasing
weight of the material and % adsorption increased with dye concentration. The conformity to both
Langmuir and Freundlich isotherm were investigated. | en_US |
