Marine Algae Biomass for Removal of Heavy Metal Ions 25.3 Experimental Methodology 615
Part D | 25.3
tive functional groups in their structure. Unfortunately,
these components are little involved in chemical binding with metal ions, because they are easily extracted
in organic and/or aqueous solvents, being responsible for the secondary pollution observed during of
the biosorption process [25.16]. Thus, by removing
such compounds by extraction with organic solvents
or alkaline treatment [25.49, 50], the main classes of
functional groups are not affected, and the obtained marine algae waste biomass has comparable or even higher
uptake capacity, for different metal ions from aqueous
solutions.
The presence of different functional groups in the
structure of marine algae and marine algae waste
biomass can be easily proved using FT-IR spectra,
recorded for dry samples. For exemplification, Fig. 25.1
illustrates the FT-IR spectra obtained for Ulva lactuca
sp. (marine green algae) before and after extraction of
oils (marine algae waste biomass).
A detailed analysis of the FT-IR spectra of these
biosorbents has indicated that in the structure of marine
algae, numerous functional groups (such as hydroxyl,
amine, carbonyl, carboxylic, sulfate) are present and
these can interact with heavy metals during the biosorption process. The same functional groups can also be
identified in the FT-IR spectra of all types of marine algae, whatever class they belong [25.26, 29, 30, 35, 48].
It was also observed that the nature of functional groups
is not changed significantly after the extraction step.
These low-cost biosorbents will act as a chemical substrate and will bond heavy metal ions from aqueous solutions by characteristic chemical (electrostatic and/or
complexation) interactions.
Although the constituents of the cell walls provide an extensive array of ligands with various functional groups capable of binding metal ions, the
role that any functional group has in the biosorption process depends on several factors. Thus, the
number of active sites on the biosorbent material surface, their accessibility and chemical state, and the
affinity of metal ions for a given functional group
play an important role in metal binding interactions,
and will influence the efficiency of the biosorption
process.
25.3 Experimental Methodology
Generally, the marine algae used as biosorbents in
the experimental studies are collected from their natural environment (seawater), washed several times with
distilled water to remove the impurities and dried in
air at 5060
ı C for 610 h, and then crushed and
sieved to a given granulation (0:51:5 mm). In the
case of marine waste algae biomass obtained after extraction steps with organic solvents and an additional
washing step with a NaOH solution is required, in
order to remove the trace of organic solvents. The
obtained materials are stored in desiccators and can
be directly used as biosorbent, without any additional
pretreatment. Because these kinds of biosorbents are
easily obtained and require only few numbers of operations, they can be included in the category of low-cost
biosorbents.
From the experimental point of view, the assessment
of a biosorption system is usually based on two types
of methodologies: equilibrium batch biosorption tests
and dynamic continuous-flow biosorption studies. Both
have several important advantages and disadvantages,
and choosing a specific methodology depends on the
objective of the study.
25.3.1 Equilibrium Batch
Biosorption Technique
The batch (or discontinue) methodology is relatively
simple and easy to use in the laboratory, especially for
the experimental study of single-metal ions biosorption.
This methodology is preferred when we want to establish the optimum conditions for retention of a given
metal ion on certain biosorbent, or to test the biosorptive performances of a new biosorbent.
In this case, a small amount of marine algae biomass
(biosorbent) is mixed with well-measured volume of
aqueous solution containing a given metal ion, in certain conical flasks, with intermittent or continuous
stirring for a required period of time. At the end of
the biosorption procedure, the biosorbent is separated
through filtration, and the concentration of the studied
metal ion in filtrate is analyzed, using an adequate analysis method.
It should be mentioned that in the biosorption
systems, the experimental parameters (solution pH,
biosorbent dose, metal ion concentration, contact time,
temperature, etc.) should be carefully controlled at the
Part D | 25.3
tive functional groups in their structure. Unfortunately,
these components are little involved in chemical binding with metal ions, because they are easily extracted
in organic and/or aqueous solvents, being responsible for the secondary pollution observed during of
the biosorption process [25.16]. Thus, by removing
such compounds by extraction with organic solvents
or alkaline treatment [25.49, 50], the main classes of
functional groups are not affected, and the obtained marine algae waste biomass has comparable or even higher
uptake capacity, for different metal ions from aqueous
solutions.
The presence of different functional groups in the
structure of marine algae and marine algae waste
biomass can be easily proved using FT-IR spectra,
recorded for dry samples. For exemplification, Fig. 25.1
illustrates the FT-IR spectra obtained for Ulva lactuca
sp. (marine green algae) before and after extraction of
oils (marine algae waste biomass).
A detailed analysis of the FT-IR spectra of these
biosorbents has indicated that in the structure of marine
algae, numerous functional groups (such as hydroxyl,
amine, carbonyl, carboxylic, sulfate) are present and
these can interact with heavy metals during the biosorption process. The same functional groups can also be
identified in the FT-IR spectra of all types of marine algae, whatever class they belong [25.26, 29, 30, 35, 48].
It was also observed that the nature of functional groups
is not changed significantly after the extraction step.
These low-cost biosorbents will act as a chemical substrate and will bond heavy metal ions from aqueous solutions by characteristic chemical (electrostatic and/or
complexation) interactions.
Although the constituents of the cell walls provide an extensive array of ligands with various functional groups capable of binding metal ions, the
role that any functional group has in the biosorption process depends on several factors. Thus, the
number of active sites on the biosorbent material surface, their accessibility and chemical state, and the
affinity of metal ions for a given functional group
play an important role in metal binding interactions,
and will influence the efficiency of the biosorption
process.
25.3 Experimental Methodology
Generally, the marine algae used as biosorbents in
the experimental studies are collected from their natural environment (seawater), washed several times with
distilled water to remove the impurities and dried in
air at 5060
ı C for 610 h, and then crushed and
sieved to a given granulation (0:51:5 mm). In the
case of marine waste algae biomass obtained after extraction steps with organic solvents and an additional
washing step with a NaOH solution is required, in
order to remove the trace of organic solvents. The
obtained materials are stored in desiccators and can
be directly used as biosorbent, without any additional
pretreatment. Because these kinds of biosorbents are
easily obtained and require only few numbers of operations, they can be included in the category of low-cost
biosorbents.
From the experimental point of view, the assessment
of a biosorption system is usually based on two types
of methodologies: equilibrium batch biosorption tests
and dynamic continuous-flow biosorption studies. Both
have several important advantages and disadvantages,
and choosing a specific methodology depends on the
objective of the study.
25.3.1 Equilibrium Batch
Biosorption Technique
The batch (or discontinue) methodology is relatively
simple and easy to use in the laboratory, especially for
the experimental study of single-metal ions biosorption.
This methodology is preferred when we want to establish the optimum conditions for retention of a given
metal ion on certain biosorbent, or to test the biosorptive performances of a new biosorbent.
In this case, a small amount of marine algae biomass
(biosorbent) is mixed with well-measured volume of
aqueous solution containing a given metal ion, in certain conical flasks, with intermittent or continuous
stirring for a required period of time. At the end of
the biosorption procedure, the biosorbent is separated
through filtration, and the concentration of the studied
metal ion in filtrate is analyzed, using an adequate analysis method.
It should be mentioned that in the biosorption
systems, the experimental parameters (solution pH,
biosorbent dose, metal ion concentration, contact time,
temperature, etc.) should be carefully controlled at the