Environmental Engineering Reference
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Posidonia oceanica
. On the other hand, in a study on the biosorption of
Acid Orange 10, Acid Red 18, and Acid Red 73 onto chitosan, Wong
et al.
[75] verified that the biosorption capacities increased when the tempera-
ture increased from 298 to 333 K. They attributed this phenomenon to
the fact that the temperature increase produces a swelling effect within
the internal structure of the chitosan, facilitating the biosorption. Also,
they affirmed that the dyes mobility was increased due to the faster rate of
diffusion of adsorbate molecules from the solution to the biosorbent. The
same dependence in relation to the temperature was observed by Reddy
et al.
[35] in the biosorption of Congo Red onto Indian Jujuba Seeds and
Mahmoud
et al.
[92] in the biosorption of Methylene Blue onto
Hibiscus
cannabinus
.
8.3.3 BiosorbentDosage
The biosorbent dosage is particularly important because it determines the
extent of decolorization and may also be used to predict the cost of bio-
sorbent per unit of solution to be treated [9]. The study of the effect of
biosorbent dosage gives an idea of the effectiveness of a biosorbent and
the ability of a dye to be adsorbed with a minimum dosage [3]. Generally,
the percentage of dye removal increases with an increase in biosorbent
dosage, since the number of biosorption sites is higher. However, the bio-
sorption capacity increases significantly as biosorbent dosage decreases,
since it is expressed in mg of dye adsorbed per gram of biosorbent. This
can be attributed to overlapping or aggregation of biosorption sites result-
ing in a decrease in total biosorbent surface area available to the dye and
an increase in diffusion path length. Zhang
et al.
[93] verified the biosor-
bent dosage effect in the biosorption of Rhodamine B (RhB) by sugarcane
bagasse. They found that the percentage of RhB removal increased from
28.0 to 99.0% when the biosorbent dosage was increased from 1 to 20 g L
-1
.
As expected, the biosorption capacity decreased from 65.7 to 11.0 mg g
-1
.
Dawood and Sen [94] verified that in the biosorption of Congo Red by pine
cone powder, an increase in biosorbent dosage from 0.01 to 0.03 g resulted
in a decrease of the amount of adsorbed dye from 13.44 to 6.28 mg g
-1
.
Elkady
et al.
[95] verified that in the biosorption of Remazol Reactive Red
198 onto eggshells, an increase in biosorbent dosage from 5 to 20 g L
-1
caused an increase in percentage of dye removal from 38 to 65%.
8.3.4 ParticleSize
The biosorbent particle size is another important effect which should be
studied. As biosorption is a surface phenomenon and can be attributed to
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