Environmental Engineering Reference
In-Depth Information
The maximum adsorption capacities for RB and BB were 179 mg g -1 (at pH
of 2) and 295 mg g -1 (at pH of 10), respectively. Furthermore, they found
that after 10 cycles of biosorption-desorption, the reduction in biosorp-
tion percentages from the 1st to 10th cycle was approximately 7% for both
dyes. Çelekli et al. [25] verified the potential of walnut husk to remove
Lanaset Red G from aqueous solutions. Based on the artificial neural net-
work studies, they verified that the pH was the most important parameter,
followed by the initial dye concentration. More information about the use
of agricultural solid wastes as biosorbents can be obtained in a nice review
recently published by Salleh et al. [3].
8.2.2 AlgaeBiomass
The term algae refers to a large and diverse assemblage of organisms that
contain chlorophyll and carry out oxygenic photosynthesis [36]. However,
in this section, blue green algae (which are cyanobacteria) are also included
because they have similar characteristics from a biosorption viewpoint.
Algae biomass has been found to be potential biosorbents because of their
availability in both fresh and saltwater [6]. This type of biomass is com-
posed mainly of proteins, carbohydrates and lipids, which contain many
functional groups such as carboxyl, hydroxyl, sulfate, phosphate, amines,
aldehydes, ketones and others [37-40]. These functional groups have high
binding affinity for SODs [12,18,19,37-42]. The dye removal by algae can
be attributed to the accumulation of dye ions on the surface of algal bio-
polymers and further to the diffusion of the dye molecules from aqueous
phase onto the solid phase of the biopolymer [6,12]. Fast and easy growth
in simple medium, low cost, availability in large quantities, high binding
affinity and renewability are some of the advantages for the use of algae
biomass as biosorbents [38,39,41,42]. Table 8.2 summarizes the biosorp-
tion capacities of algae biomass.
Dogar et al. [39] studied the biosorption of methylene blue (MB) from
aqueous solutions using green algae Ulothrix sp. They concluded that
electrostatic interactions occurred between Ulothrix sp. and MB. he
brown macroalga, Stoechospermum marginatum , was tested by Daneshvar
et al.  [42] to remove Acid Blue 25 (AB25), Acid Orange 7 (AO7) and Acid
Black  1 (AB1) from aqueous solutions. They found that the equilibrium
curves were successfully described by the Freundlich model, and the esti-
mated biosorption capacities were 22.2, 6.73 and 6.57 mg g -1 for AB25,
AO7 and AB1, respectively. Dotto et al. [43] investigated the equilib-
rium and thermodynamics of the biosorption of azo dyes onto Spirulina
platensis . They found that Tartrazine biosorption occurred by formation
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