3.1 pH
The pH of the aqueous solution (wastewater) is one the most imperative factors that
directly influences the biosorption process to remove heavy metal from wastewater.
pH affects the dissociation of functional groups of the active sites of biosorbent as
well as chemistry of ionic solution. pH optima for biosorption via algae vary from
metal to other metals. Ajayan et al. (2011) reported a significant decrease in pH
ranging from 5.6 to 8.3 while removing heavy metal from tannery wastewater. Ritixa
and Monika (2013) reported that pH optima for iron and copper were 8 for both with
removal efficiency of 92–93%, respectively, in biosorption process. Dominic et al.
(2009) reported that pH level of industrially polluted wastewater shows a drift from
acid to alkaline, i.e., 6.0–8.1, after treatment with Chlorella vulgaris. Wastewater
treatment with Synechocystis salina shows a slight drift in pH from 6.0 to 8.0, while
the same wastewater shows variation in pH decrease (from 6.0 to 7.9) treated with
different algal species Gloeocapsa gelatinosa. Therefore, it is clear from the above
explanation that changes in pH have substantial potential to alter the biosorption
potential through various processes such as affecting ionic chemistry and metal
availability in medium and affecting algal growth in case of active algal biomass.
3.2 Temperature
The biosorption of heavy metals through algae is unaffected within the temperature
ranging from 20 to 35
C, while at 40–50
C, biosorption efficiency increased, but
such high temperatures may be responsible for permanent structural damage to the
Cell surface
adsorption
Bioaccumulation
Intracellular
Ligands
Vacuole
Ion exchange
Cation
exchange
Electrostatic
Interactions
HM
+
HM
+
HM
+
HM +
HM +
HM
+
HM
+
HM
+
HM
+
HM
+
C
Precipitation
Surface
complexation
SO 4
RCOOR 2 OSO 3 -
–NH 2
–SH
Efflux
Fig. 3.5 Mechanism of physical adsorption of heavy metals. (Ayansina and Olubukola 2017)
3 Phycoremediation: Algae as Eco-friendly Tools for the Removal of Heavy. . .
61
The pH of the aqueous solution (wastewater) is one the most imperative factors that
directly influences the biosorption process to remove heavy metal from wastewater.
pH affects the dissociation of functional groups of the active sites of biosorbent as
well as chemistry of ionic solution. pH optima for biosorption via algae vary from
metal to other metals. Ajayan et al. (2011) reported a significant decrease in pH
ranging from 5.6 to 8.3 while removing heavy metal from tannery wastewater. Ritixa
and Monika (2013) reported that pH optima for iron and copper were 8 for both with
removal efficiency of 92–93%, respectively, in biosorption process. Dominic et al.
(2009) reported that pH level of industrially polluted wastewater shows a drift from
acid to alkaline, i.e., 6.0–8.1, after treatment with Chlorella vulgaris. Wastewater
treatment with Synechocystis salina shows a slight drift in pH from 6.0 to 8.0, while
the same wastewater shows variation in pH decrease (from 6.0 to 7.9) treated with
different algal species Gloeocapsa gelatinosa. Therefore, it is clear from the above
explanation that changes in pH have substantial potential to alter the biosorption
potential through various processes such as affecting ionic chemistry and metal
availability in medium and affecting algal growth in case of active algal biomass.
3.2 Temperature
The biosorption of heavy metals through algae is unaffected within the temperature
ranging from 20 to 35
C, while at 40–50
C, biosorption efficiency increased, but
such high temperatures may be responsible for permanent structural damage to the
Cell surface
adsorption
Bioaccumulation
Intracellular
Ligands
Vacuole
Ion exchange
Cation
exchange
Electrostatic
Interactions
HM
+
HM
+
HM
+
HM +
HM +
HM
+
HM
+
HM
+
HM
+
HM
+
C
Precipitation
Surface
complexation
SO 4
RCOOR 2 OSO 3 -
–NH 2
–SH
Efflux
Fig. 3.5 Mechanism of physical adsorption of heavy metals. (Ayansina and Olubukola 2017)
3 Phycoremediation: Algae as Eco-friendly Tools for the Removal of Heavy. . .
61