BIOSORPTION PERFORMANCE OF A BINARY METAL MIXTURE BY ALGAL BIOMASS: COLUMN EXPERIMENTS

Raw seaweed Gelidium sesquipedale and a composite material prepared from an industrial algal waste have been converted into inexpensive biosorbents, which were used for removal of Pb

2+

/Cd

2+

from aqueous solutions. The equilibrium data follow a multi-component discrete model and indicate a good adsorption capacity. The biosorption behavior of both materials during one sorption-desorption cycle of Pb

2+

/Cd

2+

has been investigated in a packed-bed flow-through column. In the sorption process, Cd breaks through the column faster than Pb due to its low affinity. An overshoot in the outlet Cd concentration was observed and explained by ion exchange between Pb and Cd, whereby the higher affinity of the Pb ion displaces the Cd ion bounded to the biosorbent. A 0.1 M HNO

3

solution was used as eluant for the desorption process. Desorption was 100% effective for Cd and Pb. A mass transfer model for the adsorption and desorption processes was used to simulate the column performance.