Highly Deacetylated Chitosan as Low-cost Adsorbent Material for Removal of Heavy Metals from Water

Background and Aim: Chitin, a naturally occurring polysaccharide was isolated from the shells of crabs. The chitin was chemically modified to give alkali chitin, carboxymethyl chitin, highly deacetylated CM chitosan and highly deacetylated chitosan. The highly deacetylated chitosan was used as an adsorbent for removal of heavy metals from surface and groundwater samples collected from Lagos metropolis.

Experimental: The process was performed by using chitosan to reduce the concentration of heavy metals from the water samples by packing a column with the chitosan in a burette. 100 ml of the water samples were passed through the packed column and 2.5 ml of concentrated nitric acid was added to the filtrate in a 250 ml beaker. The mixture was evaporated on a hot plate to about 20 ml. The filtrate was transferred to a 100 ml volumetric flask and it was diluted to the mark and mixed thoroughly. A portion of the digested samples was taken for required metal determination using Atomic Absorption Spectroscopy.

Results: The heavy metal adsorption capacity of the deacetylated chitosan was assessed by running surface and groundwater samples through a column packed with deacetylated chitosan. The percentage removal of Pb, Cd and Cu from the water samples was as follows; lead in the borehole (57%), lagoon (39%), well water (8%). cadmium in borehole (80%), lagoon (43%), well water (54%) and copper in borehole (61%), lagoon (44%) and well water (0%).

The chemical integrity of the chitin derivatives was confirmed through IR studies.