Abstract:
In this research work natural bio polymer “chitosan” was synthesized using locally available
shrimp shells and adsorption of chromium by chitosan was studied. Synthesize of chitosan
involved four main stages as preconditioning, demineralization, deprotenisation and
deacetylation. “Preconditioning” process is a new step introduced in this research, to remove
loosely bound protein. In the preconditioning, the skeletal matrix structure is first weakened
which makes easier to remove soluble protein by washing with water. Therefore during
deproteination process less alkali concentration can be used. Effect of deacetylation
conditions such as alkali concentration, number of times of deacetylation performed and
reaction temperature was investigated. Chitosan was characterized using Fourier Transform
Infrared Spectroscopy (FTIR), Differential Thermal analysis (DTA), Thermal Gravimetric
Analysis (TGA) and X-ray diffraction (XRD). These characterization techniques confirm the
existence of chitosan. Degree of deacetylation was calculated using FTIR spectra. This value
was highly depending on reaction temperature, reaction time, alkali concentration and
number of times of deacetylation. Both characterization techniques confirm the existence of
chitosan.
The affinity of chitosan for chromium was studied using K2Cr2O7 solution as the heavy metal
solution containing Cr (VI) ions. Adsorption of chromium ions by chitosan was investigated
under different conditions. The effect of reaction temperature, particle size of chitosan and
pH of solution were studied. Amount of chromium absorbed under different conditions was
evaluated using atomic absorption spectroscopy.
