Part D | 25.4
618 Part D Marine Algal Biotechnology
process is lower due to the decrease of the specific surface area. Thus, for the best mass transfer and utilization, the biosorbent granules should
be as small as possible. Practically, the recommended biosorbent dimension rages between 0:5 and
2:0 mm.
The main disadvantage of using marine algae
biomass in dynamic continuous-flow biosorption systems is the easy with which the column is clogged,
due to the small size of biosorbent. In consequence,
the flow rate of aqueous solution through the column will be obstructed, and thus the efficiency of
the biosoption process will be drastically affected.
To solve this problem, some studies from the literature have proposed the conversion of marine algae
biomass into granules by including them in various
organic polymer matrices (see Table 25.3). But, by
using this procedure, some functional groups from
the marine algae biomass surface become unavailable for the heavy metal ions from aqueous solution, because they are blocked by interactions with
the polymer matrix. This makes the biosorption capacity of marine algae biomass decrease, and the
efficiency of the biosorption process in continuousflow conditions less than those obtained in batch systems [25.65]. In order to avoid this inconvenience,
Bulgariu and Bulgariu [25.42] propose the mixing of
marine algae waste biomass with commercially available anion exchanger resin (Purolite A-100), and the
obtained biosorbent mixture has proven to be efficient in the removal of Pb(II) ions from aqueous
media. Because on this resin the retention of Pb(II)
ions is insignificant, it can be considered an inert
material, which has the role to prevent the clogging
of the column, due to the larger size of its particles. In addition, the Purolite A-100 resin has an excellent retention capacity for some inorganic anions
(such as nitrate or sulfate) [25.81], which are also
present in wastewater and are also pollutants for aquatic
environment.
25.4 Influence of Experimental Parameters
The removal of heavy metal ions from aqueous solutions by biosorption on marine algae biomass takes
places with maximum efficiency only in well-defined
experimental conditions. In consequence, an important part of the studies related to the removal of
heavy metal ions by biosorption on low-cost materials such as marine algae biomass was the study
of the influence of several experimental parameters
on the retention process efficiency. As a function
of the experimental technique used in the biosorption studies, the experimental parameters that should
be considered in the experimental studies are as
follows:
i) For batch technique – solution pH, biosorbent dose,
initial metal ion concentration, contact time between the two phases, and temperature.
ii) For the dynamic continue-flow technique – height
of biosorbent bed, aqueous solution flow rate, and
initial concentration of heavy metal ions.
The experimental results obtained in these studies
have provided a complete view of the biosorption process and allowed us to establish the optimal conditions
for that the removal efficiency of metal ions from aqueous solutions is maximum.
25.4.1 Influence of Experimental
Parameters on Batch-Technique
Effect of Solution pH
The pH of heavy metal ions solutions is the most important experimental parameter that governs the biosorption process. When designing a process for metal ions
removal from wastewater, both optimal pH value for
metal biosorption and pH value required for effluent
discharge to comply with regulation must be taken into
consideration before making a final decision [25.82].
Many studies from the literature [25.16, 28–38]
have shown that the low-cost materials, including marine algae and marine algae waste biomass, act as
a good biosorbent in a rather narrow pH range. The solution pH strongly influences not only the dissociation
degree of functional groups from biomass surface, considered as biosorption sites, but also the solution chemistry of heavy metal ions (hydrolysis, complexation
by organic and/or inorganic ligands, redox reactions,
precipitation, etc.), the speciation and the biosorption
availability of the heavy metals [25.83–85].
In Sect. 25.2 it was already shown that the marine algae and marine algae biomass contains in their
structure various functional groups (such as carboxyl,
hydroxyl, amino, sulfate). With the change in the so-
618 Part D Marine Algal Biotechnology
process is lower due to the decrease of the specific surface area. Thus, for the best mass transfer and utilization, the biosorbent granules should
be as small as possible. Practically, the recommended biosorbent dimension rages between 0:5 and
2:0 mm.
The main disadvantage of using marine algae
biomass in dynamic continuous-flow biosorption systems is the easy with which the column is clogged,
due to the small size of biosorbent. In consequence,
the flow rate of aqueous solution through the column will be obstructed, and thus the efficiency of
the biosoption process will be drastically affected.
To solve this problem, some studies from the literature have proposed the conversion of marine algae
biomass into granules by including them in various
organic polymer matrices (see Table 25.3). But, by
using this procedure, some functional groups from
the marine algae biomass surface become unavailable for the heavy metal ions from aqueous solution, because they are blocked by interactions with
the polymer matrix. This makes the biosorption capacity of marine algae biomass decrease, and the
efficiency of the biosorption process in continuousflow conditions less than those obtained in batch systems [25.65]. In order to avoid this inconvenience,
Bulgariu and Bulgariu [25.42] propose the mixing of
marine algae waste biomass with commercially available anion exchanger resin (Purolite A-100), and the
obtained biosorbent mixture has proven to be efficient in the removal of Pb(II) ions from aqueous
media. Because on this resin the retention of Pb(II)
ions is insignificant, it can be considered an inert
material, which has the role to prevent the clogging
of the column, due to the larger size of its particles. In addition, the Purolite A-100 resin has an excellent retention capacity for some inorganic anions
(such as nitrate or sulfate) [25.81], which are also
present in wastewater and are also pollutants for aquatic
environment.
25.4 Influence of Experimental Parameters
The removal of heavy metal ions from aqueous solutions by biosorption on marine algae biomass takes
places with maximum efficiency only in well-defined
experimental conditions. In consequence, an important part of the studies related to the removal of
heavy metal ions by biosorption on low-cost materials such as marine algae biomass was the study
of the influence of several experimental parameters
on the retention process efficiency. As a function
of the experimental technique used in the biosorption studies, the experimental parameters that should
be considered in the experimental studies are as
follows:
i) For batch technique – solution pH, biosorbent dose,
initial metal ion concentration, contact time between the two phases, and temperature.
ii) For the dynamic continue-flow technique – height
of biosorbent bed, aqueous solution flow rate, and
initial concentration of heavy metal ions.
The experimental results obtained in these studies
have provided a complete view of the biosorption process and allowed us to establish the optimal conditions
for that the removal efficiency of metal ions from aqueous solutions is maximum.
25.4.1 Influence of Experimental
Parameters on Batch-Technique
Effect of Solution pH
The pH of heavy metal ions solutions is the most important experimental parameter that governs the biosorption process. When designing a process for metal ions
removal from wastewater, both optimal pH value for
metal biosorption and pH value required for effluent
discharge to comply with regulation must be taken into
consideration before making a final decision [25.82].
Many studies from the literature [25.16, 28–38]
have shown that the low-cost materials, including marine algae and marine algae waste biomass, act as
a good biosorbent in a rather narrow pH range. The solution pH strongly influences not only the dissociation
degree of functional groups from biomass surface, considered as biosorption sites, but also the solution chemistry of heavy metal ions (hydrolysis, complexation
by organic and/or inorganic ligands, redox reactions,
precipitation, etc.), the speciation and the biosorption
availability of the heavy metals [25.83–85].
In Sect. 25.2 it was already shown that the marine algae and marine algae biomass contains in their
structure various functional groups (such as carboxyl,
hydroxyl, amino, sulfate). With the change in the so-