Biomedical Engineering Reference
In-Depth Information
and the surface tension was reduced to 29 mN/M. The biosurfactant produced consisted of
four different fengycin A homologues and thus has potential for oil removal from sludges.
NEW TECHNOLOGIES
New developments have been made in the area of biosurfactants with regard to
nanotechnology. Nanorods of NiO were produced by a water-in-oil microemulsion
(Palanisamy, 2008) and a biosurfactant was subsequently added to heptane. The pro-
duced nanorods were 22 nm in diameter and 150-250 μm in length at pH 9.6. This
could be due to the effect of pH on the biosurfactant morphology. The use of the
biosurfactant is a more eco-friendly approach.
Reddy et al. (2009) showed that the synthesis of silver nanoparticles could be sta-
bilized by surfactin. These nanoparticles have unique physical, chemical, magnetic,
and structural properties. Various pH and temperature conditions were evaluated.
The nanoparticles were stabilized for a period of 2 months by surfactin, which is a
stabilizing agent that is renewable, has low toxicity, and is biodegradable, and is thus
an environmentally friendly additive.
Rhamnolipid was evaluated for its effect on the electrokinetic and rheological
behavior on nanozirconia particles (Biswas and Raichur, 2008). The biosurfactants
adsorb increasingly onto the zirconia as the concentration increases. The biosur-
factant was able to disperse the zirconia particles at pH 7 and above as shown by
zeta-potential measurements, sedimentation, and viscosity tests. It can serve as an
eco-friendly product for flocculation and the dispersion of high solid contents of
microparticles.
Fatisson et al. (2010) evaluated various components on the stabilization of
CMC-coated zero-nonvalent iron nanoparticles (nZVI). Stabilization is important
to enhance the transport of the nZVI particles to the zone of contamination. The
effects of fulvic acid and rhamnolipid were evaluated as these are naturally found in
the groundwater and soil environment. The presence of the rhamnolipid led to the
lowest rate of deposition of the particles on silica.
Fe/Ni particles were used to degrade PCE extracted by soil washing of various
surfactants (Vipulanandan and Harendra, 2008). Within 45 min, CTAB extracted
(280 mg/L of PCE), SDS (240 mg/L PCE) and UH biosurfactant (214 mg/L PCE)
were completely degraded. More recent work by the same authors (Vipulanandan
and Harendra, 2011) examined the in situ degradation of PCE with a surfactant-
bimetallic nanoparticle colloidal solution. The colloidal solution was transported
through a clayey soil in a soil column. The UH biosurfactant-Fe/Ni colloidal solu-
tion decreased PCE by 82%, compared to 77% by the CTAB Fe/Ni colloidal solution.
Laboratory experiments were conducted to investigate the effect of the presence of
rhamnolipid on the production and stabilization of iron nanoparticles (Farshidy et al.,
2011). In addition, the effect of rhamnolipid on the remediation of chromium (VI) from
water using iron nanoparticles was tested. Iron nanoparticles were produced in the pres-
ence of different concentrations of rhamnolipid. Then, unmodified nanoparticles were
treated with different concentrations of rhamnolipid and carboxymethyl cellulose. The
TEM micrographs indicated that without adding rhamnolipid during the production pro-
cess, the size of iron nanoparticles is high due to the formation of micron-sized clusters.
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