Geosynthetics October/November 2021 - 24

Hybrid GCLs for attenuation of PFAS in landfill leachates
1000
100
and not enough meso- and micropores
may result in a lower adsorption capacity.
When looking at PFAS, generally a good
balance of each size category results in
optimized adsorption.
AC can be manufactured from virtually
10
1
0.1
0.01
Leachate A
Leachate B
Leachate C
Perfluorobutane sulfonic acid (PFBS)
Perfluoropentane sulfonic acid (PFPeS)
Perfluorohexane sulfonic acid (PFHxS)
Perfluorooctane sulfonic acid (PFOS)
Perfluorobutanoic acid (PFBA)
Perfluoropentanoic acid (PFPeA)
Leachate D
Leachate E
Perfluorohexanoic acid (PFHxA)
Perfluoroheptanoic acid (PFHpA)
Perfluorooctanoic acid (PFOA)
4:2 Fluorotelomer sulfonic acid (4:2 FTS)
6:2 Fluorotelomer sulfonic acid (6:2 FTS)
Leachate F
FIGURE 4 PFAS concentrations of various Australian landfill leachates under study
any organic material. Because of their high
carbon contents, however, wood, coconut
shells and coal are the most used raw
materials. Activation may be carried out
by chemical means or, more commonly,
by high-temperature steam > 1,292°F (>
700°C) in a controlled atmosphere. There
are important differences between AC produced
from wood, coconut shells and coal.
Wood-based AC generally has a higher
level of macropores whereas coconutbased
AC has a higher level of micropores.
Coal-based AC is comprised of a good balance
of micro- (small), meso- (medium)
and macro- (large) pores, making it a
solid contender for efficient adsorption of
certain organic molecules, such as PFAS
(Nowicki et al. 2014).
Coals are classified according to their
age. Lignite, or brown coal, is the youngest
type of coal followed by subbituminous,
bituminous and anthracite. The origin
and age of the coal is a key factor in producing
an AC with a very high specific
surface area and a good particle size distribution
(PSD). Bituminous coal-based
AC has been shown to have superior performance
in trapping a wide range of
perfluorinated compounds over other AC
varieties (McNamara et al. 2018).
One of the earlier GCL modification
FIGURE 5 Part of the upgrade undertaken at the Geofabrics Australasia Pty Ltd. South
Queensland Manufacturing facility to blend bentonite and additives, allowing customization
of the hGCL according to site chemistries analyzed in the company's GRID R&D lab.
trials included a 3.24 ounces per square
yard (110 g/m2), 15.75 mil (0.4 mm)
thick AC cloth placed within the GCL
beneath the geotextile cover layer. This
data demonstrated that the addition of
an AC interface attenuated the PFOA,
PFOS and PFHxS further than what was
observed in the initial investigations
with the standard and PMB GCLs. PFOS
again was reduced to less than the LOR,
PFOA reduced to 0.25 ppb (0.25 µg/L)
24
Geosynthetics | October November 2021
Concentration (μg/L)

Geosynthetics October/November 2021

Table of Contents for the Digital Edition of Geosynthetics October/November 2021

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Geosynthetics October/November 2021 - 1
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