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

Scenedesmus exists comonly in the plankton of freshwater ponds, rivers, and
lakes, and occasionally in brine environments. Its location starting from all of North
America from tropical to arctic climates. In nutrient-rich waters, the growth of the
biomass might be dense. As in the case of other algae types, it is an leading producer
and it has food source property for higher trophic degrees.
The genus, Scenedesmus, is frequently utilized as a bioindicator for the
detection of nutrients or toxins coming from anthropogenic inputs to aqueous media.
For example, Scenedesmus produces phytochelatin when the metal content of the
medium is increased.
1.6. Use of Immobilized Biomass in Biosorption
One of the major problems in the use of algae for the biological treatment of
wastewaters is their recovery from the treated effluent. So as to solve the problems
associated with the harvesting the biomass, many systems have been proposed or
tried (Olguin 2000). Among the most recent ways of passing this problem are
immobilization techniques applied to algal cells. In fact, in the case of photosynthetic
cells, over the last 20-25 years considerable progress has been achieved in the
immobilization of photobiologhical organisms and organelles such as cyanobacteria,
photocynthetic bacteria, algae and chloroplasts.
1.6.1. Immobilization Techniques
Since the microbial biomass is composed of small particles with low density,
poor mechanical strength and little rigidity, to use the biomass in the treatment
process cell immobilization becomes an emerging path for the elimination of the
problem. The cell immobilization is an interesting method to fix and retain biomass
on appropriate natural or synthetic materials support by performing a range of
physical and biochemical procedures. The immobilization of the biomass in materials
leads to the formation of a material having a tunable size, mechanical strength and
rigidity and porosity which is required to accumulate the metals. Immobilization of
the biomass can produce beads and also granules, this materials could be activated
and used repetitively like in a similar way of ion exchange resins and activated carbon.
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