Utilization of Cyanobacterium phormidium sp. to produce immobilized hybrid disc biosorbent for the removal of Cd²⁺ from aqueous solution

摘要

An indigenous strain of blue green microalga was entrapped within reticulated fibrous network of loofa sponge disc to produce immobilized hybrid disc biosorbent (IHDB) and successfully used for the removal and recovery of Cd2+from aqueous solution. The two biosorbents used as the symbiotic building block to produce IHDB, were the filamentous blue green alga Phormidium sp. (B1) and loofa sponge discs (B2). Maximum biosorption capacity of B1 and B2 was noted respectively to be 37.06 and 5.32 mg Cd2+g-1biosorbent. However, when the two biosorbents were combined to form IHDB, the biosorption capacity (48.53 mg g-1) was increased by 30.95%, 812.21%, respectively as compared to the ability of B1 and B2 when used alone, and by14.51% than the sum of individual abilities of the two biosorbents. The kinetics of Cd2+removal by IHDB was rapid, with 91.81% of Cd2+biosorption occurring within first 30 min., and equilibrium was reached after 60 min of contact. The Langmuir and Freundlich adsorption isotherm models were used for mathematical description of the sorption equilibrium. Equilibrium data fitted very well to the Langmuir model in the studied range of concentration (5-200 mg l-1). The biosorbed Cd2+was desorbed by washing the IHDB with dilute HCl (50 mM) and regenerated IHDB was reused in seven biosorption-desorption cycles without an apparent decrease in metal biosorption capacity. The metal removing capacity of IHDB was also tested in continuous flow fixed-bed column bioreactor and found to be highly effective in removing Cd2+from aqueous solution. The results suggested that IHDB could be used as low-cost and environment-friendly biosorbent for the efficient removal of Cd2+from aqueous solution.