Alginate was reagent grade (300–400 cP) of Wako
Pure Chemicals (Tokyo, Japan) and used without further
purification. Fig. 1 shows a schematic diagram of a
device for the preparation of alginate beads. An alginate
solution (2 wt.%) was sprayed through a thin inner
nozzle (£ 0.8 mm) into a 150 mM calcium chloride
solution with nitrogen gas blown from an outer space of
the nozzle. The resultant beads were allowed to stand in
the solution for 24 h at room temperature with gentle
agitation on a magnetic stirrer. After being washed with
deionized water, the beads were sieved between 16 mesh
(0.991 mm) and 32 mesh (0.495 mm). The Hþ form of
the beads was obtained by immersing the beads three
times in 0.1 M HCl. After being extensively washed with
deionized water, the beads were used for sorption
experiments.
polluted streams in response to growing environmental
legislation and enforcement. In addition, groundwater
often contains iron and manganese, which cannot only
affect the flavor and color of water but also accumulate
to cause obstruction in the water equipment and pipelines.
Conventional methods employed to remove heavy
metals contained in water streams include chemical precipitation,
filtration, electrodialysis, and ion exchange.
However, electrodialysis and ion exchange plants have
high maintenance and operation costs. Chemical precipitation
is inexpensive but incapable of removing trace
levels of heavy metal ions.
Adsorption is expected to overcome such impediments,
having a wide variety of applications. Of many
sorbents, utilization of naturally occurring materials has
been recognized as a way of reducing waste treatment
cost (Bailey et al., 1999). Alginate, which is a polysaccharide
biopolymer composed of varying compositions
of b-1,4 linked D-mannurinic and L-guluronic acids