Biosorption studies for removal of chromium using immobilized marine alga Isochrysis galbana

Abstract

A new biosorbent material marine micro alga Isochrysis galbana, from marine sources Bay of Bengal, was immobilized and used as an adsorbent for removal of chromium. It was found that the increase in aqueous metal concentration increased metal uptake within the range of present study. The presence of acid decreased metal uptake probably due to the preferential adsorption of hydrogen ion compared to chromium ion. The immobilized calcium alginate beads were also found to adsorb chromium in absence of biomass as well and presence of biomass increased the metal adsorption by 3-4 fold. This immobilized biomass was very effective for the removal of chromium. Isochrysis galbana was found to adsorb chromium more strongly when compared to another marine micro alga, Chaetoceros calcitrans, probably due to presence of polysilicate layers over Chaetoceros cells and also due to larger size of Chaetoceros cells. Equilibrium distribution data were best correlated by Freundlich type of equation for the range of experimental parameters covered in the present study. An empirical equation was proposed to estimate the equilibrium metal concentration in the immobilized algal beads (CS) as a function of pH and aqueous metal concentration (CA).