● Álvarez Jove Keyla Ester
● Hernández Miranda Keren María
● Miranda Arrieta Esteban José
● Petro Cantero Reny Sofía
● Suárez Zúñiga Luz Dey
Professor: Monica Cecilia Cantero Benites
In situ soil flushing to
remediate confined soil
contaminated with PFOS- an
innovative solution for
emerging environmental
issue

1. INTRODUCTION
Perfluorooctane sulfonate (PFOS) is a toxic
anthropogenic chemical
Soil and groundwater
remediation strategies
● For soil remediation, activated carbon
(AC) and montmorillonite
● For groundwater remediation,
extraction with ion exchange resins,
nonionic exchange resins, and AC
adsorption. Other, such as thermal
treatment, chemical oxidation methods
and bioremediation. ETC
In situ soil flushing is a mature technology to remediate soil contaminated
with various organic and inorganic contaminants as it requires minimum
excavatio, in addition, it involves minimum disturbance to the existing soil
structure

2. METHODOLOGY
2.1. Proposed stages in the in situ flushing process
1- Solvent recovery
2- water treatment
3- mix treated water with organic
solvent
4- spray the contaminated soil with
the prepared solvent
5- transfer PFOS from soil to water
6- pump the contaminated water.
Fig. 1. Suggested process of in situ flushing technology to
remediate PFOS contaminated soil

2.2. Adsorbent pre-treatment
2.3. Soil collection,
preparation and analysis
● K6362, Amberlite IRA 67, PFA694E, MP 62,
Dowexoptopore V493, Dowexoptopore L493,
Dowex MarathonA, Jacobi, Filtrasorb 400,
Ovivo, Amberlite XAD 2, Amberlite IRA400
and Amberlite XAD 4)
● The filter materials were washed with deionized
water
● The activated carbon types were first rinsed
with deionized water and then washed in
deionized water at 80 °C for 2 h.
● They were then dried in an oven at 105 °C for
48 h, crushed in a mortar and passed through a
0.25-0.5 mm sieve.
● A mini excavator was used
● They were stored in airtight polypropylene.
● They were air dried, homogenized and
passed through sieves.
● The solid-liquid extraction method was used
● The soil samples were placed in
polypropylene bottles.
● 100 ml of methanol were added
● Shaken for 24 hours and centrifuged
● The samples were analyzed by mass
spectrometry.

2.4. Isothermal and kinetic experiment

2.5. Optimization of washing solvents and resins

2.6. Column experiment
The soil physical
characteristics of the site were
simulated in the column by
accurately maintaining soil
density, moisture content, and
permeability.
Fig. 2. A schematic view of the column
experiment test.

3. RESULTS AND
DISCUSSION.
3.1. Potential site to implement the
method
137 groundwater samples were
collected from existing boreholes in
the contaminated site and analysed
for PFOS concentration using EPA
method 537
Fig 3. Frequency distribution of PFOS
concentrations in the analysed samples.
The median PFOS level measured in
this study was 64 times higher than
the guideline set for drinking water.

3.2.Solvent optimisation
Fig 4. Variation of equilibrium liquid phase PFOS concentration
with various solvent concentrations of Ethanol, Methanol and
Propanol.
50% ethanol is selected
due to its better
dissipation efficiency,
lower environmental
and human toxicity than
methanol (metabolic
acidosis, renal failure
and blindness) and its
very frequent
application in other
studies.

It was observed that over
45%, 75% and 82% of PFOS
was eliminated by the first,
second and third bed volumes,
respectively. Less than 2% of
PFOS was retained in the soil
after five bed volumes of
solvent flushing.
Fig 5. Efficiency of PFOS removal from column experiment on
sandy soil.
3.3.Column experiment

3.4. Resin optimisation
They showed comparatively
higher adsorption capacity and
faster adsorption kinetics.
3 types of granular
activated carbon (GAC)
The commercially available
granular sorbent "Jacobi"
showed better performance
than the other two types of
GAC.
3 types of non-ion
exchange resins
Amberlite IRA400 and
Amberlite XAD 4, showed a
PFOS adsorption capacity 2 to 3
times higher than that of
Jacobi.
7 types of ion exchange
resins

Table 1
Freundlich constants and Pseudo-second-order kinetic parameters for PFOS with different adsorbents.
Kinetic characteristics and isotherms of PFOS for
various granular materials available on the market.
PFOS adsorption capacity of adsorbents ↓ pH increases.
Monovalent and divalent cations such as K + , Na + , Mg 2+ and Ca
2+↑ cap. adsorption of PFOS from the adsorbent

The effectiveness of a method in soils with high
permeability.
The heterogeneity of the soil prevents the uniform
distribution of the sln. of washing.
Porosity is reduced-surfactants adhere to soil
particles.
PFAS and solvent can migrate to other areas-
vadose zone-subterranean.
Loss of groundwater quality due to solvents.
The containment of soil contaminated with PFAS
prevents migration of contaminants.

Bibliography
Senevirathna, S. T. M. L. D., Mahinroosta, R., Li, M., & KrishnaPillai, K. (2021). In situ soil flushing to remediate confined
soil contaminated with PFOS-an innovative solution for emerging environmental issue. Chemosphere, 262, 127606.