5 Environmental Application of Biosurfactants
5.1 Use of Biosurfactant in Contaminated Soils
Majorly, common heavy metals found in contaminated soils are mercury (Hg), lead
(Pb), arsenic (As), chromium (Cr), cadmium (Cd), zinc (Zn), nickel (Ni), and copper
(Cu), which can cause many health issues and environmental hazards (Adamu et al.
2015; Hu et al. 2017; Li and Qian 2017; Liu et al. 2015, 2017; Tang et al. 2015). In
the removal of heavy metals from contaminated soil by using a biosurfactant
solution, three main steps are involved. First, the heavy metals adsorbed on the
surface of contaminated soil particles separate through the sorption of biosurfactant
molecules at the interfaces between metal in aqueous solution and wet soil (sludge).
Then, the metal will be absorbed by biosurfactants and trapped within the micelle
through electrostatic interactions. Finally, through the method of membrane separation, the biosurfactant can be recovered (Guan et al. 2017; Ibrahim et al. 2016).
Biosurfactants were also found to be a good agent to improve and augment soil
properties, including via their bioremediation capacities. In situ bioremediation
application of biosurfactants were influenced by soil properties, C:N ratio, and
other factors, such as inherent temperature, pH, etc. Vecino Bello et al. (2012)
postulated on the influence of pH, salinity, and temperature of soil on the bioremediation capabilities of L. pentosus biosurfactant, and also these parameters
impacted the surface tension of the biosurfactant; besides these soil parameters,
the emulsifying capacity of this biosurfactant was impacted by operation time
(Vecino et al. 2014).
Biosurfactants produced by microorganisms are reported to modify the physical
properties of soil. Lin et al. (2017) noted the effect of the rhamnolipid (125 and
625 mgL
À1 ) in lowering flow rates (cmh
À1 ) in soil when packed with it than rather
with CaCl 2 and FeCl 3 ; thus, the biosurfactant limited the soil permeability. In
another study, Rufino et al. (2011) gauged the role of Candida lipolytica
biosurfactant in hydraulic conductivity; these attributes of biosurfactants varied on
the soil texture, long compounding with the dosage involved and other features of
biosurfactants (Abu-Zreig et al. 2003). Another insight is the ability of plant roots to
hold the biosurfactant in the rhizosphere, impacting the retention and enhancing
plant’s capability to siphon the moisture and nutrients from the soil micropores. Soil
hydrophobicity is a significant factor in land management, and it is accessed by
wettability (measured by wettability angle). Surfactants were noted for their impact
to alter this wettability of soils (Akbulut et al. 2012). Hallmann and Mędrzycka
(2015) assayed the performance and power of rhamnolipid on contact angle on soil
surfaces and proved that, at a minimal load of rhamnolipid, it impacted the contact
angle. Al-Wahaibi et al. (2014) published a study wherein B. subtilis B30 accomplished lipopeptide biosurfactant 58.7
in the wettability of soils. As with the case of
other applications of biosurfactants, the wettability effects of biosurfactants also
18
K. Mulugeta et al.
5.1 Use of Biosurfactant in Contaminated Soils
Majorly, common heavy metals found in contaminated soils are mercury (Hg), lead
(Pb), arsenic (As), chromium (Cr), cadmium (Cd), zinc (Zn), nickel (Ni), and copper
(Cu), which can cause many health issues and environmental hazards (Adamu et al.
2015; Hu et al. 2017; Li and Qian 2017; Liu et al. 2015, 2017; Tang et al. 2015). In
the removal of heavy metals from contaminated soil by using a biosurfactant
solution, three main steps are involved. First, the heavy metals adsorbed on the
surface of contaminated soil particles separate through the sorption of biosurfactant
molecules at the interfaces between metal in aqueous solution and wet soil (sludge).
Then, the metal will be absorbed by biosurfactants and trapped within the micelle
through electrostatic interactions. Finally, through the method of membrane separation, the biosurfactant can be recovered (Guan et al. 2017; Ibrahim et al. 2016).
Biosurfactants were also found to be a good agent to improve and augment soil
properties, including via their bioremediation capacities. In situ bioremediation
application of biosurfactants were influenced by soil properties, C:N ratio, and
other factors, such as inherent temperature, pH, etc. Vecino Bello et al. (2012)
postulated on the influence of pH, salinity, and temperature of soil on the bioremediation capabilities of L. pentosus biosurfactant, and also these parameters
impacted the surface tension of the biosurfactant; besides these soil parameters,
the emulsifying capacity of this biosurfactant was impacted by operation time
(Vecino et al. 2014).
Biosurfactants produced by microorganisms are reported to modify the physical
properties of soil. Lin et al. (2017) noted the effect of the rhamnolipid (125 and
625 mgL
À1 ) in lowering flow rates (cmh
À1 ) in soil when packed with it than rather
with CaCl 2 and FeCl 3 ; thus, the biosurfactant limited the soil permeability. In
another study, Rufino et al. (2011) gauged the role of Candida lipolytica
biosurfactant in hydraulic conductivity; these attributes of biosurfactants varied on
the soil texture, long compounding with the dosage involved and other features of
biosurfactants (Abu-Zreig et al. 2003). Another insight is the ability of plant roots to
hold the biosurfactant in the rhizosphere, impacting the retention and enhancing
plant’s capability to siphon the moisture and nutrients from the soil micropores. Soil
hydrophobicity is a significant factor in land management, and it is accessed by
wettability (measured by wettability angle). Surfactants were noted for their impact
to alter this wettability of soils (Akbulut et al. 2012). Hallmann and Mędrzycka
(2015) assayed the performance and power of rhamnolipid on contact angle on soil
surfaces and proved that, at a minimal load of rhamnolipid, it impacted the contact
angle. Al-Wahaibi et al. (2014) published a study wherein B. subtilis B30 accomplished lipopeptide biosurfactant 58.7
in the wettability of soils. As with the case of
other applications of biosurfactants, the wettability effects of biosurfactants also
18
K. Mulugeta et al.