Abstract:
Unmodified and aminated chitosan were used for the removal of phosphate from aqueous
solution. The unmodified and aminated crab shell chitosan were characterized by using infra-red
spectrophotometry, scanning electron microscope and X-ray diffractogram. The results show that
there were IR spectra that indicated the presence of amine in the aminated chitosan. The scanning
electron micrographs indicate increase porosity as a direct consequence of the loaded amine groups
attached to unmodified chitosan and the maximum peaks absorption correlates with the standard
XRD of chitosan. Phosphate removal was carried out under various experimental conditions by
varying the pH, contact time, biomass dose, concentration and temperature. Adsorption data have
been interpreted in terms of Langmuir and Freundlich equations. The results obtained provided
strong support for the adsorption of phosphate onto the biomass and was found to fit sufficiently
to the Freundlich isotherm but fairly to Langmuir isotherm model. The sorption kinetics was tested
using the pseudo-first-order and pseudo-second order models and good correlation coefficients
obtained for the pseudo-second-order kinetics model shows that phosphate uptake process
followed the pseudo-second-order rate expression. Results obtained showed that maximum
adsorption of 3.83mg/g and 3.92mg/g takes place at pH 3 for unmodified chitosan and aminated
chitosan and the optimum time for unmodified chitosan is 120 min while that of aminated chitosan
is 300 min, Varying the adsorbent biomass dosage shows increase in adsorption capacity (66.88%
- 86.88% for unmodified chitosan and 76.12% - 86.34% for aminated chitosan) with increase in
biomass dosage. Evaluation of thermodynamic parameters showed that the adsorption process is
endothermic and non-spontaneous in nature.
