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學生:陳雅貞
日期:2010.12.14
Introduction
Polycyclic aromatic hydrocarbons (PAHs) are pollutants of
major concern in soils and sediments.
Surfactant-enhanced remediation (SER) has been suggested as
a promising technology for the removal of hydrophobic
pollutants from soil and groundwater.
surfactants are viewed as being potentially useful for aiding
the bioremediation of PAH-contaminated sites.
Introduction
In practical applications, mixtures of surfactants, rather than
individual surfactants are often used.
Anionic–nonionic surfactants reduced precipitation and
sorption loss, and enhanced the flushing and washing
efficiency for contaminated soils.
The surfactants, TW80, TX100, Brij35 and SDS were selected
because they have been extensively used in bioremediation
trials and are likely to be degraded in the environment.
Introduction
• The objectives of the present study are (1) to quantify the
extent of phenanthrene solubilization in mixed anionic–
nonionic surfactants; (2) to evaluate the biodegradation of
phenanthrene associated to the mixed micellar phase by
phenanthrene-degrading microorganisms.
Materials
• Phenanthrene (purity > 98%)
• Sodium dodecyl sulfate；SDS(purity>98%)
• Brij35
• TW80
• TX100
• HPLC-grade methanol
Experimental section
Measurement of surface tension and CMC
The CMC values were
obtained through a
conventional plot of the
surface tension versus the
logarithm value of the
surfactant concentration.
都諾表面張力測定儀
Experimental section
Solubilization test
Phenanthrene in solutions was analyzed at
single/mixed
surfactant solutions
254nm
Prepared at the total
concentration
Separate the undissolved
of phenanthrene
5.0 and 10.0mM
phenanthrene
The
(Mmixed
surfactant
was
separately
added
to solutions)
each tube in an
the molar ratios of SDS
amount slightly more
to nonionic surfactant
than required to
were 1:0, 9:1, 7:3, 5:5,
saturate the solution
3:7, 1:9 and 0:1.
，25 ±and
1 ℃surfactant–
1.0ml of 48h
methanol
water Solution diluted to 10ml.
Experimental section
Biodegradation test of phenanthrene
The biodegradation experiments in the
dark to avoid photooxidation of
phenanthrene.
Diluted with methanol and
filtered through 0.22μm syringe
filter.
Surfactant solution and fine
phenanthrene in the sealed flasks were
shaken and then filtered to separate he
crystalline particles
Ultraviolet spectrophoto detector
high-pressure liquid chromatography
mineral basal medium solution
microorganism solution
The filtrate was transferred into flask.
Results and discussion
• The surface tensions at a
given molar ratio decreased
The
CMCstotal
were
withmixed
increasing
intermediates
between the and
surfactant concentration,
eachofsurface
tension curve
CMCs
the individual
SDS and
had a breaking point that was
TX100.
taken as a mixed CMC.
Fig. 1. Plots of surface tension versus the
total concentrations of SDS-TX100.
For SDS-TW80 and SDS-Brij35
systems, similar tendency was
observed, but slightly different
from SDS-TX100.
Results and discussion
During
the formation
surfactant
When Xnon
was 0.9, of
themixed
mixedmicelle,
CMC ofnonionic
SDS-TW80
and SDSmolecules
insert
into the
micelle
of anionic
surfactant
andBrij35,
decrease
Brij35 were
somehow
less
than those
of pure
TW80 and
the
repulsion force among the ionic heads.
respectively.
Results and discussion
Solubililzation of phenanthrene
The solubilities of phenanthrene
were enhanced by each of surfactant
solutions, in which the solubilities
increased with increasing surfactant
concentrations.
Fig. 2. Solubilization of phenanthrene by single
surfactants
Results and discussion
SPAH,cmc (M) is the apparent solubility of a PAH compound at the CMC.
SPAH,cmc(M) is the total apparent solubility of the PAH compound in micellar solution at
a particular surfactant concentration greater than the CMC.
Csurf is the surfactant concentration at which SPAH,mic was evaluated.
surfactant
TW80
MSR
0.165
Brij35
＞
0.124
TX100
＞
0.0949
SDS
＞ 0.0243
Results and discussion
Fig. 3. Synergistic solubilization of phenanthrene by
mixed surfactants, (a) SDS-TW80
The compositions of mixed systems,
Smix is greater than Scal.
(c) SDS-Brij35
(b) SDS-TX100
Results and discussion
Ideal additivity rule
Snon is the apparent solubility of phenanthrene in sole nonionic surfactant solution.
the apparent solubility in sole SDS solutions.
the intrinsicsolubility of phenanthrene in water (1.18mgL-1，25 ℃)
Results and discussion
The degree of phenanthrene
solubility enhancements by mixed
surfactants (Smix)followed the order
of SDS-TW80 > SDS-Brij35 >
SDS-TX100.
The degree of synergistic
Th
evalues of Risshows
SDSsolubilization
relativethat
large
when
Brij35
exhibits
Xnon is
small. larger extent of
synergistic solubilization, which
may be attributed to the same alkyl
chain in the molecular structures of
Brij35 and SDS.
Results and discussion
Biodegradation of phenanthrene
Surfactants may improve the mass
transfer of solid hydrocarbons, there
nonionic
surfactant to
with
byMixing
increasing
the availability
SDS
mixed micelle CMC , as
microorganisms.
mentioned
bioavailability
However,above,
with high
CMC and
of
.
lowphenathrene
solubilizing capacity,
SDS
would not enhance availability of
contaminants significantly.
Fig. 4. Degradation of phenanthrene
in single or mixed surfactants. (a)SDS
Results and discussion
That 17.39mgl-1 of phenanthrene in
0.5mM (655mgl-1) of TW80
solution disappeared within 60h.
The degrading rate of phenanthrene
was slightly faster in 2.0–0.5mM of
SDS-TW80 solution.
Fig. 4. Degradation of phenanthrene in
single or mixed surfactants. (b) TW80
and SDS-TW80.
A large amount of phenanthrene
(26.80mgL-1) in 5.0–0.5mM of
SDS-TW80 was degraded with 96h.
Results and discussion
SDS-TX100 systems, the
degradation rates of phenanthrene
in 2.0–1.0 and 5.0–1.0mM of SDSTX100 systems were at large the
same as that in 1.0mM (625mgl-1)
of TX100.
Fig. 4. Degradation of phenanthrene in single
or mixed surfactants (c) TX100 and SDS-TX100.
Results and discussion
Phenanthrene in 1.0mM of Brij35
solutions was depleted within 36h.
24.50mgl-1 of phenanthrene in 2.0–
1.0mM of SDS-Brij35 solution
disappeared at 48h.
The microorganisms took up about
96h to consume 33.32mgl-1 of
phenanthrene in 5.0–1.0mM of
SDS-Brij35 solution.
Fig. 4. Degradation of phenanthrene in single
or mixed surfactants. (d) Brij35 and SDSBrij35.
Results and discussion
When the concentration of
SDS increased, phenanthrene
degradation could slow down.
The application of surfactants
to soil environments
contaminated with PAHs has
become a possible means to
increase the bioavailability of
these hydrophobic
compounds and to facilitate
their biodegradation.
Conclusions
• The experiment showed that CMCs of mixed surfactants are
much lower than that of individual SDS.
• The solubility of phenanthrene was proportional to the
concentration of the single surfactants when above the CMC.
• On the basis of MSR, solubilization capacity for phenanthrene
was in the order: TW80 > Brij35 > TX100 > SDS.
Conclusions
• Given the molar fraction of nonionic surfactant and the total
surfactant concentrations,SDS-TW80 enhanced the solubility
of phenanthrene most significantly among three mixed systems,
while SDS-Brij35 exhibited larger extent of synergistic
solubilization.
• In view of the biodegradation experiments, phenanthrene
in mixed surfactant solutions was readily degradable during
the experiment.
Conclusions
• No inhibitory effects on the microorganism duo to the
mixing of SDS with TW80, TX100 and Brij35 were
found.
• These results suggest the mixed surfactant solution may
improve the performance of SER by increasing the
bioavailability and biodegradation of PAHs and reducing
the level of remediation expanses.