BIOSORPTION OF Pb2+, Cd2+, & Ni2+ FROM WATERS BY ...

2.6.2. Immobilization of Biosorbents into Agarose
Another immobilization method was also applied in which the algae was fixed
in agarose (Lopez et al. 1997) (Figure 2.2 shows the structural unit of agarose (1 4)-
3,6-anhydro-α-L-galactopyranosyl-(1 3)-β-D-galactopyranan). For this purpose, 2.0 g
of agarose were dissolved in 90 mL of distilled water by heating at 100°C and after
cooling to 40°C, 10 mL of cell suspension (1 g dry weight/10 mL) were added and
mixed. The aqueous phase and the oily phase (vegetable oil, e.g. olive or sunflower),
in a proportion of 10:1, were placed in a funnel (15 cm diameter) connected to a
plastic tube closed with forceps (Figure 2.3). The cell-polymer mixture was added
dropwise rapidly into the oil-water mixture, and the polymerization/solidification
took place in the oily phase. When all gel-beads had been passed through the
interface they were collected directly in the aqueous phase at the end of the plastic
tube attached to the funnel. The gel-beads and a part of the aqueous phase were
collected in a container. To eliminate the oily phase, the gel-beads were washed once
with Triton X-100 (0.01 %) and three times with ultra-pure water. Blank agarose
beads were also prepared without the addition of algae. Then, the beads were dried at
40ºC in an oven, and agarose immobilized with algae was used in the sorption
experiments.
Figure 2.2. The structural unit of agarose.
28