ADSORBENTS FOR CD REMOVAL FROM WATER WASTE: A SHORT REVIEW OF THE RECENT DEVELOPMENT - Management of Hazardous Residues Containing Cd - page 29

Özer t al. [115] studied the removal of Cd 2+ using inactivated Cladophora
crispata , a kind of green algae. They studied the pH influence of the medium
on Cd 2+ adsorption onto inactivated Cladophora crispate and they determined
that the optimum initial pH value was 5.0. The kinetic studies indicated that
the equilibrium time for Cd 2+ adsorption on C. crispata was 20 min and the
adsorption capacity was 28 mg g -1 .
Gélabert et al. [125] studied the Cd 2+ adsorption using diatom-water
interfaces for two marine planktonic ( Thalassiosira weissflogii and
Skeletonema costatum ) and two freshwater periphytic species ( Achnanthidium
minutissimum and Navicula minima ). The authors observed that the
dependence on the surface adsorption constants with various environmental
factors (pH, ionic strength, metal speciation and biomass concentration,
temperature, light) is the key parameter in the knowledge of the adsorption
process.
Protonated biomass of the seaweed Sargassum miticum was investigated
for its ability to remove cadmium (II) from aqueous solutions [126]. The
adsorption process is relatively fast, especially at pH 3, where 90% of the
equilibrium uptake is achieved in the first 20min. When the pH is 4, the
system takes more than 75 min to adsorb an identical percentage of the
metallic ion. The maximum uptake obtained was 134.8 mg g -1 at pH 4.5.
Oscillatoria sp. H1 (cyanobacteria, microalgae) was used for Cd 2+
removal from aqueous solutions in the following ways: dry biomass, alive and
heat-inactivated immobilized form on Ca-alginate [127]. The maximum
adsorption was observed at pH 6.0 and it took 1 h to reach the biosorption
equilibrium. The maximum biosorption capacities for plain alginate beads, dry
biomass, immobilized live Oscillatoria sp. H1 and immobilized heat-
inactivated Oscillatoria sp. H1 were 21.2, 30.1, 32.2 and 27.5 mg g -1 ,
respectively. The alginate-algae beads were regenerated using 0.1 M HCl
aqueous solution with about 85% of the recovery.
The sorption of Cd 2+ onto dried green macroalga Caulerpa lentilifera was
investigated by Pavasant et al. [128]. The analysis with FT-IR indicated that
O-H, N-H, N-H, C-N, C-O, S=O and S-O were the possible functional
groups involved in metal sorption by this alga. The sorption of metal ions
rapidly reached equilibrium within 20 min. The maximum adsorption capacity
was 4.7 at pH 5.
Lodeiro et al. [129] studied the Cd 2+ adsorption capacities of five different
brown seaweeds. The maximum adsorption capacities at pH 4.5 of Bifurcaria
bifurcata, Saccorhiza polyschides, Ascophyllum nodosum, Laminaria