ABSTRACT
This study was carried out to investigate the removal of chromium (VI) from chromate solution using deacetylated chitin extracted from mussel shell. Mussel shells were obtained from Gubi dam in Bauchi, Nigeria and chemical method was used to extract chitin and then chitosan from these shells. The mussel shell contained 15.14% chitosan as obtained from the proximate analysis. The extracted chitosan was characterised and used for removal of Cr6+ from dichromate - water solution of 0.62 mg of Cr6+ per litre of deionised water. The results obtained revealed that the Carbon-Nitrogen ratio of deacetylated chitin was 5.9, with a degree of deacetylation (DDA) of 60.69% and 60.66% as calculated from elemental analysis and FTIR spectra of chitosan respectively. The surface area of the chitosan was determined to be 2.7225 � 0.0741 m2/g using the BET machine. The optimum chitosan dosage for chromium removal was found to be 2.5 g at 28 oC with a Cr6+ removal of 82.3%, the time required for equilibrium to be attained was 80 minutes. The Langmuir isotherm was the best fitted isotherm with an R2-value of 0.983 and the adsorption process follows the pseudosecond order kinetics with an R2-value of 0.9997, the adsorption process was established to be reversible with an RL-value of 0.314. The free sorption energy was (0.224 kJ/mol) which suggests the process was physical. The enthalpy of adsorption was -67.295 kJ/mol K and the Gibbs free energies were all negative, thus the process is spontaeneous and exothermic. The concentration of chromium (VI) ion was successfully reduced via adsorption from the chromium solution using the extracted chitosan from mussel shell.