Chemical Geology 279 (2010) 106–119
Contents lists available at ScienceDirect
Chemical Geology
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c h e m g e o
Composition effects on synthetic glass alteration mechanisms: Part 1. Experiments
Natarajan Rajmohan, Pierre Frugier, Stephane Gin ⁎
CEA Marcoule, DTCD/SECM/LCLT, BP 17171, 30207 Bagnols-sur-Cèze Cedex, France
a r t i c l e
i n f o
Article history:
Received 21 January 2010
Received in revised form 29 September 2010
Accepted 13 October 2010
Editor: J.D. Blum
Keywords:
Glass
Nuclear glass
Alteration
Dissolution
Kinetics
Gel
Passivating layer
GRAAL
a b s t r a c t
Alteration of nuclear waste glasses and silicate minerals is governed by complex processes regulated by
several coupled mechanisms. Among these processes is reactive mass transfer through the amorphous gel
layer (known as the passivating reactive interphase (PRI) in case of a rate-limiting effect) located between the
pristine glass and the bulk solution. In order to assess the influence of the glass composition and the pH on the
properties of the PRI, and thus on the nuclear glass durability, an experimental leaching study was performed
on borosilicate glass samples with or without Ca, Al, and Zr. Experiments were conducted to understand the
influence of the pH and glass composition on the solvated cation diffusion coefficient within the PRI and to
generate data for calibration of a PRI solubility model (not presented here). All the experiments were carried
out at high S/V ratios so that silicon rapidly reached apparent saturated conditions and the PRI could form: in
such conditions glass alteration is controlled only by diffusion of water and dissolved species through the PRI
and by precipitation of crystallized secondary phases. The constituents in the PRI and the crystallized
secondary phases depend to a large extent on the glass composition and pH. Alkali metal (Na) or
preferentially alkaline earth (Ca) elements are retained in the PRI for charge compensation of Al and Zr. The
apparent diffusion coefficient calculated from the release of boron, a good tracer, varies with the pH from less
than 4 × 10−22 to 9 × 10-18 m2 s−1 in the studied glasses. These very low diffusion coefficients decrease as the
pH increases. Concerning the PRI composition we show that Si, Al, Ca and Zr have strong interactions and thus
major consequences on the glass durability. Our findings indicate that the SiO2aq activity is relatively constant
and independent of the pH below pH 9, followed by a drop at pH 10. In addition, the activity of SiO2aq is
affected by the glass composition, and especially by aluminum and zirconium. As soon as dissolved silicon
reaches steady state in solution the aluminum and zirconium concentrations start to decrease, probably due
to silicon, aluminum and zirconium interactions with retention in the PRI. The formation of crystallized
secondary phases is observed at pH 10 for aluminum-free glasses, which diminishes the saturation state of
amorphous silica in solution. In these glasses the saturation index indicates that the solution is oversaturated
with respect to calcium silicate hydrates (ex: tobermorite, gyrolite). Moreover, the formation of crystallized
secondary phases causes dissolution of the PRI and the glass, which sustains renewed alteration. This study
leads to the conclusion that modeling nuclear glass dissolution kinetics over a wide pH range (typically from
pH 7 to pH 10) must take into account (1) PRI composition variations and relations between the PRI
composition and properties (solubility, diffusion coefficient); and (2) crystallized secondary phases that can
consume elements from the PRI. Applying PRI modeling concepts to other kinds of natural glasses or even
multi-oxide minerals might prove useful for enhancing our understanding of alteration mechanisms.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
Many fields of research are concerned by water–rock interactions
ranging from global cycling of elements to the transport of
groundwater nutrients and contaminants. Mineral surface descriptions are required to understand the mechanisms involved. In France,
one reference option for the management of vitrified high-level waste
packages is deep geological disposal (waste management act of June
28, 2006). The current disposal concept studied by ANDRA (French
⁎ Corresponding author.
E-mail address: [email protected] (S. Gin).
0009-2541/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.chemgeo.2010.10.010
National Radioactive Waste Management Agency) is based on three
containment barriers: the glass package (inside its stainless steel
canister), a 55 mm thick carbon steel overpack, and finally the host
rock which is a 130 m thick Callovo-Oxfordian argillite layer (ANDRA,
2005). Based on the calculations for the safety assessment of a
geological repository, the most important phenomena that must be
thoroughly investigated concern radionuclide release from the glass
matrix due to alteration by groundwater and migration through the
host rock. In either normal or accident scenarios, these phenomena
will take hundreds of thousands of years before the radionuclides
reach near-surface aquifers. This is why a comprehensive methodology is required, including laboratory experiments to investigate
chemical processes at different scales, a mechanistic model to predict
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
the radionuclide source term, and model validation using natural or
archeological analogs, integrated mockups or in situ tests.
Dissolution of silicate glasses is a complex process controlled by
several mechanisms (Conradt, 2008; Frugier et al., 2008; Frizon et al.,
2009). The alteration kinetics of silicate glasses determined from
laboratory studies involve several characteristic process steps that are
detailed below (Advocat et al., 1991; Berger et al., 1987; Byers et al.,
1985; Crovisier et al., 1985, 1989, 1992; Guy, 1989; Vernaz and
Dussossoy, 1992; Verney-Carron et al., 2007; Van Iseghem et al.,
2007). Recently, Frugier et al. (2008) proposed a new mechanistic
model called GRAAL (Glass Reactivity with Allowance for the Alteration
Layer), which highlights the key mechanisms in the glass alteration
process. This model has been applied successfully to SON68 glass (i.e.
the French inactive reference glass) altered in various conditions
(Frugier et al., 2009). In the GRAAL paradigm, the glass alteration
process is a combination of the following steps: (1) exchange and
hydrolysis reactions first involve mobile glass components (alkali
metals, boron, etc.) (Geneste et al., 2006; Rebiscoul et al., 2007);
(2) hydrolysis, especially of silicon, results in the existence of an initial
glass dissolution rate; (3) the difference between these two kinetics
causes an amorphous alteration layer to form at the glass/solution
interface regardless of the alteration conditions; (4) the amorphous
alteration layer progressively creates a barrier limiting the transport of
water toward the glass and of solvated glass ions into solution; (5) some
glass constituents precipitate as crystallized secondary phases which are
present on the external surface or dispersed in solution. Depending on
their composition, the formation of these crystallized secondary phases
may accelerate or maintain a pseudo-constant glass alteration rate. The
“final” or “residual” alteration rate can be attributed to the mechanisms
of steps (4) and (5). Overall, glass alteration produces an amorphous
alteration layer (often called the “gel”) as well as crystallized secondary
phases, and these two phenomena are of a completely different nature
(Thomassin, 1984; Jercinovic et al., 1990, Advocat et al., 1991, Vernaz
and Dussossoy, 1992; Verney-Carron et al., 2007).
According to basic thermodynamics, the amorphous layer is
stable only when the solution is saturated with respect to its constituent elements such as silicon, zirconium, aluminum, calcium, etc.
Furthermore, the transport-inhibiting effect of the amorphous layer
between the glass and solution controls glass alteration (i.e. the
release of glass alteration tracers like boron or alkalis). The
amorphous layer is therefore termed a “passivating reactive interphase” (PRI) in accordance with its properties (Chave et al., 2007;
Frugier et al., 2008). However, a low-density amorphous layer can
form far from saturation thanks to low-solubility elements such as Zr.
Under these conditions, it has no or negligible passivating properties
compared with the PRI that is eventually formed at saturation. It is
then called a depleted gel. The nature of the amorphous layer varies
with the reaction conditions (glass-surface-area-to-solution-volume
(S/V) ratio, flow rate, pH, temperature, etc.) and with the reaction
progress (forward rate, rate drop or residual rate regimes). At high S/V
ratios the system reaches saturation very rapidly, hence only the PRI is
observable and the depleted gel is not significant (b1 nm) (Frugier
et al., 2008). Moreover, Rebiscoul et al. (2005) carried out a detailed
investigation of the amorphous layer and its properties in different
reaction conditions, reporting that the amorphous layer has two
different parts: a porous layer in contact with water and a dense layer
at the gel-glass interface. Furthermore, the dense zone is identified as
the one controlling the residual rate, which is expected to be the most
important regime in a geological repository.
Numerous studies have reported the role of the amorphous layer
and its protective properties on the alteration of glass or silicate
minerals (Angeli et al., 2001; Ledieu et al., 2005; Hellmann et al., 2003,
2004; Lee et al., 2007; Rebiscoul et al., 2005). Some studies
investigated the amorphous layer characteristics and its structural
rearrangement during alteration, porosity, diffusion properties,
retention of elements in the amorphous layer, etc. (Arab et al.,
107
2008; Jollivet et al., 2008; Houston et al., 2008; Angeli et al., 2001b,
2008; Chave et al., 2007). Nevertheless, the composition of the
amorphous layer has still not been fully defined. Generally, the
amorphous layer is depleted in highly soluble elements and enriched
in sparingly soluble elements. The constituents of the amorphous
layer vary with glass composition, pH, temperature, etc. (Angeli et al.,
2006, 2008). However, silicon, aluminum and zirconium are the
predominant elements in the amorphous layer when SON68-type
nuclear waste glasses undergo alteration. Element interactions within
the amorphous layer are also an important factor; for example, in
aluminosilicate glasses, silicon and aluminum strongly interact in the
amorphous layer. Houston et al. (2008) studied the interaction
between aluminum and amorphous silica using bulk solution
chemistry experiments with NMR techniques. They reported three
reaction pathways for aluminum–silica interactions such as adsorption of Al at surface silanol sites, surface-enhanced precipitation of
aluminum hydroxides and aluminosilicate secondary phases. Several
researchers have documented the role of dissolved aluminum on
aluminosilicate mineral dissolution reactions (Oelkers and Schott,
1994; Bickmore et al., 2006; Chou and Wollast, 1985; Samson et al.,
2005; Jones and Handreck, 1963; Hingston and Raupach, 1967; Ballou
et al., 1973; Iler, 1973; Van Bennekom et al., 1991; Van Cappellen and
Qiu, 1997). They concluded that Al species diminish the silica or
silicate mineral dissolution rates in different reaction conditions.
Because the time scale considered for geological disposal is
inaccessible to laboratory experimentation, modeling is the principal
method used to assess the overall glass alteration behavior. Geochemical
models are widely employed to simulate crystallized secondary phase
formation during glass alteration (Advocat et al., 2001; Berger et al.,
1987, 1994; Crovisier et al., 1985, 1989, 1992; Gislason et al., 1993; Gong
et al., 1998; Grambow et al., 1985; Michaux et al., 1992,). These studies
examined and simulated the dissolution kinetics and the formation of
crystallized secondary phases, but the simulation did not take into
account the formation of an amorphous layer at the glass/solution
interface. Munier et al. (2004) modeled the amorphous layer composition of simple borosilicate glasses by the precipitation of an ideal solid
solution. They considered three types of solid solutions: oxides,
hydroxides and metasilicates. The major limitation of this work concerns the phases considered for the amorphous layer. Except for amorphous silica, silicates cannot form an amorphous layer. Furthermore, the
present work will show that sodium is not retained as sodium oxide or
hydroxide or silicates, but only as a charge compensator of Al and Zr in
the amorphous layer. Moreover, if calcium is present in the glass
constituents, most of the sodium will not remain in the amorphous
layer. In addition, the chemical interactions between elements such as Si,
Al, Ca, Zr within the amorphous layer were not considered in this study.
Likewise, in the GRAAL model (Frugier et al., 2009), the amorphous layer
(PRI) consists of simple phases which represent its forming elements
such as Si, Al, Ca and Zr, and does not take into account the chemical
interactions between these elements.
Hence, the present study was carried out to model the PRI
composition of French nuclear waste glasses (stoichiometry similar to
SON68) using simple and complex phases which represent PRIforming elements and their chemical interactions. This study focuses
on the main PRI-forming constituents of SON68 type glass: Si, Al, Zr
and Ca. The study combines experiments and modeling. Experiments
were carried out to understand the influence of the pH and glass
composition on the diffusion coefficient and glass alteration phenomena, and to generate data for model calibration and validation. The pH
range was chosen to cover alteration conditions imposed by the
groundwater (pH near neutrality in most cases) up to conditions
imposed by the glass dissolution (pH around 9.5). As the PRI is by
definition (Frugier et al., 2008) the most passivating amorphous layer
eventually formed in silicon-saturated condition, all the experiments
were carried out at a high S/V ratio (2000 m−1) and at 90 °C. In these
conditions, saturation is achieved in a few hours; consequently, the
108
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
amorphous layer contains negligible amounts of depleted gel.
Moreover, the activity of its constituents (Si, Al, Ca, Zr) will remain
almost constant after a few hours so that we may consider the
amorphous layer is homogenous PRI for modeling purpose.
Table 1
Glass composition (oxide wt.%/mol%).
a
Glass
SiO2
CJ2
CJ3
CJ4
CJ7
CJ8
CJ9
SON68a
61.2
58.1
56.2
59.1
62
59.8
45.5
B2O3
64.9
61.2
60.1
63.8
63.7
62.5
50.5
18.9
17.9
17.3
18.2
19.1
18.5
14.0
Na2O
17.3
16.3
16.0
17.0
16.9
16.7
13.4
13.3
12.6
12.2
12.8
13.4
13.0
9.9
SON68 contains other minor elements.
Al2O3
13.6
12.9
12.6
13.4
13.3
13.2
10.6
6.6
6.3
6.1
6.4
4.9
CaO
4.1
3.9
3.8
4.1
3.2
ZrO2
5.2
5.0
5.8
5.7
5.5
5.3
4.0
6.1
5.9
4.8
3.3
3.5
1.7
1.8
3.5
2.7
1.8
1.5
2. Methodology
2.1. Experimental procedure
2.1.1. Glass details
Table 1 indicates the glasses used in this study and their
composition. The detailed procedure for glass specimen preparation
Fig. 1. Equivalent thicknesses of elements versus time for CJ2, CJ3 and CJ8 glasses at pH 7. S/V = 2000 m−1, temperature 90 °C. Similar trends are observed in other glasses (CJ2 = CJ7,
CJ3 = CJ4 and CJ8 = CJ9).
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
is given in Jégou et al. (2000) and Gin and Jégou (2001). The glasses
were fabricated in an induction-heated furnace at 1500 °C. Rayleigh–
Brillouin light scattering was used to measure the glass homogeneity.
The 100 − 125 μm and 20 − 40 μm size fractions were obtained by
crushing glass rods in a ball mill followed by sieving. The powder
samples were washed in acetone, alcohol, and finally in ultrapure
water. The specific surface area of the sample was determined by BET
method using Kr.
The stoichiometry of these glasses is based on the SON68 glass
composition. In order to understand the effect of Ca, Al and Zr, glasses
109
were prepared by adding their oxides to the three major oxides Si, B
and Na (Table 1).
2.1.2. Alteration methods
Experiments were carried out in a static system using PTFE reactors
(Savillex) at 90 °C. Glass samples with size fractions 100 − 125 μm and
20− 40 μm were selected for this study. Static leaching experiments
were carried out for about 150 days at a glass surface-area-to-solutionvolume (S/V) ratio of 2000 m−1 except for CJ9 (4800 m−1) and with
various imposed pH values (7, 8, 10) at 90 °C. This covers the pH range
Fig. 2. Equivalent thicknesses of elements versus time for CJ2, CJ3 and CJ8 glasses at pH 10. S/V = 2000 m−1, temperature 90 °C. Similar trends are observed in other glasses
(CJ2 = CJ7, CJ3 = CJ4 and CJ8 = CJ9).
110
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
expected in an argillaceous geological repository (Bildstein et al., 2007).
Experimental data for these glasses at pH 9 were taken from Jégou
(1998) and Gin and Jégou (2001). For pH 7 and 8, 0.2 mol of tris
(hydroxymethyl)aminomethane (TRIS) buffer solution was prepared in
0.1 mol/L and 0.01 mol/L HNO3 solutions, respectively. Potassium
hydroxide (KOH 0.028 mol/L) solution was used as a buffer for pH 10
experiments. In order to avoid the large pH adjustment, buffer solutions
were directly used as the solvent for all the leaching experiments. The
quantity of buffer solutions needed for each reaction was calculated
with the JCHESS code (van der Lee et al., 2003). Buffer solutions were
heated to 90± 1 °C before addition to the reactor to avoid the initial
delay in the reaction. After adding the glass powder and solvent, reactors
were kept in 1000 mL PTFE reactors with a small quantity of water to
prevent evaporation loss of the reaction solution. Solutions were not
stirred during the experiment.
2.1.3. Sampling and chemical analysis
Two milliliters of solution was sampled from the reactor and
ultrafiltered to 10 000 Da, and then acidified with 3 mL of 0.5 N HNO3
to prevent the formation of colloids. The solution samples were
refrigerated at 4 °C pending analysis. Analysis was carried out using
inductively-coupled plasma atomic emission spectrometry (ICP-AES)
for cations (Si, B, Na, Al, Ca, K) and ion chromatography for chloride.
Fig. 3. Boron equivalent thickness versus time for different glasses and pH. Data for initially pure water leading to a pH close to 9 collected from Gin and Jégou (2001) and Jégou et al. (2000).
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
The uncertainty on these data is generally 3%, although potentially
higher for low Al concentrations.
2.2. Solid characterization
Altered glass samples were collected from the reactor and
characterized by SEM (JEOL JSM6330F, 15 kV, EDS analysis with PGT
system). We carried out direct observations of the altered grain
surface to view the crystallized secondary phases. Samples were
carbon coated prior to analysis. The altered glass powder was also
characterized by X-ray diffraction (Philips X'Pert).
2.3. Data analysis
Elemental analysis results were employed to calculate the altered
glass percentage, altered glass equivalent thickness, diffusion coefficient, and retention factor.
The altered glass percentage (AGB%) was estimated from the boron
solution analysis by iteratively calculating the leached fraction
without omitting all mass losses due to sampling. Boron is generally
selected for such calculations because it is not retained in secondary
phases and is one of the first leached components (Scheetz et al.,
1985). AGB% was calculated at each sampling interval using the
following relation:
mleached
mleached
boron
=
=
AGB % = boron
m0boron
m0glass ⋅xB
t
t
t−1
i
i
CB ⋅V + ∑ CB ⋅ VSV
i=1
m0glass ⋅ xB
ð1Þ
where CBi is the boron concentration (g/m3) at time i in solution, CBt is
the boron concentration (g/m3) at time t in solution, V t is the solution
t
volume (m3) remaining in the reactor at time t, VSV
is the solution
3
0
volume (m ) sampled at time t, mglass is the initial mass of glass
powder (g), and xB is the boron mass fraction in the glass (g/g).
The altered glass equivalent thickness Eq(B) (m−1) calculated
from mobile element (B) is given by
!
dEqðBÞ
d
Ct
t B t
=
dt
dt xB S = V ρ
ð2Þ
111
is mainly an amorphous phase that grows within the volume of altered
glass.
The retention factor (RF) for element i in the glass alteration
products is calculated using the following relation:
RFi = 1−
EqðiÞ
EqðBÞ
ð5Þ
where Eq(i) is the equivalent thickness of element i.
The diffusion coefficient of boron through the PRI was determined
using Fick's second law by the following relation (Chave et al., 2007):
rffiffiffiffiffiffiffiffi
DB t
π
EqðBÞ−EqðSiÞ = 2
ð6Þ
where Eq(B) − Eq(Si) is the equivalent gel thickness, DB is expressed
in (m2/s) and t is the time (s). During glass alteration, once saturation
with respect to PRI is achieved, the boron concentration increases only
due to the diffusion process (Frugier et al., 2008). As long as saturation
with respect to the PRI is not reached, boron also enters solution due
to the PRI dissolution process. Consequently, the equivalent thickness
calculated from silica must be subtracted from the equivalent
thickness calculated from boron to obtain a better estimate of the
diffusion coefficient. This equation is a valid approximation as long as
the amount of silica in secondary phases is negligible compared to the
amount of silica in solution, and as long as the amount of silica in
solution is negligible compared to the amount of silica in the PRI.
The chemical analysis results were employed to calculate the
activity of individual species and the saturation index of minerals in
solution using the JCHESS code (van der Lee et al., 2003; Wolery, 1992).
The saturation index shows whether the water will tend to dissolve or
precipitate a particular mineral. Its value is negative when the mineral
may be dissolved, positive when it may be precipitated, and zero when
the water and mineral are at chemical equilibrium. The saturation
index (SI) is calculated by comparing the chemical activities of the
dissolved ions of the mineral (ion activity product, IAP) with their
solubility product (Ksp). In equation form, SI = log(IAP/Ksp).
where ρ is the glass density (g/m3). Eq. (2) defines the altered glass
equivalent thickness based on the mass balance of elements between
the solid and the solution. Another equation (Eq. (3)) can be derived
for the same purpose. It is assumed that glass grains are perfect
spheres and have the same specific surface area, Sp (m2/g). Based on
this assumption, the altered glass equivalent thickness (Eq(i)) is
obtained from the altered glass percentage (AGi%) (Chave et al.,
submitted for publication).
1=3
R0
EqðiÞ = 1−ð1−AGi %Þ
R0 =
3
ρSp
ð3Þ
ð4Þ
As mentioned earlier, boron is a good tracer of glass alteration
because it is not retained in the alteration products (PRI and crystallized
secondary phases) (Scheetz et al., 1985). Based on solubility data,
condensation/precipitation of boron may only be observed at very high
boron concentrations in solution to precipitate phases such as borax
(Na2B4O7 •10H2O) or colemanite (Ca2B6O11•5H2O). Such concentrations
are rarely obtained during glass alteration processes and have never
been observed in our experiments. The consequence is that equivalent
thicknesses calculated for boron do in fact represent the amount of glass
that has been altered whatever the underlying mechanism. It is a good
approximation of the thickness of the amorphous layer when the latter
Fig. 4. Altered glass percentage at the 150th day, calculated for boron, for studied
glasses and various pHs.
112
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
3. Experimental results
3.1. Glass alteration at various pH values
Fig. 1 illustrates the evolution curve for equivalent thicknesses of
elements (see Eqs. (1) and (3)) as a function of time for three of the
six glasses studied. Only glasses CJ2, CJ3 and CJ8 are shown in Fig. 1
because the element leaching trends in CJ2 and CJ7, CJ3 and CJ4, and
CJ8 and CJ9 are similar. Furthermore, the element leaching trends are
similar at pH 7 and pH 8. In CJ2, at pH 7, the boron and sodium trends
are similar, continuously increasing but at a decreasing rate (Fig. 1,
CJ2). A similar observation can be made for CJ3 glass. In CJ8 and CJ9,
the curves for boron and sodium are completely different from the
other glasses. Early dissolution of these elements is high: the
Fig. 5. Scanning electron microscope images (15 kV) of altered glass surface (CJ8 (a), CJ9 (b)) and XRD patterns (CJ8 and CJ9 (c)) at pH 10, S/V = 2000 m−1, temperature 90 °C,
duration 150 days. Secondary phases are likely calcium silicate hydrates (CSH).
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
equivalent thickness is around 400 nm at pH 7 and 500 nm at pH 8.
However, after reaching these values, the boron and sodium
equivalent thicknesses remain stable without fluctuations.
In CJ3 and CJ8, the equivalent thicknesses of boron and sodium are
identical, which indicates that boron and sodium are leached
congruently. However, this is not observed in calcium-free glasses.
Indeed, in CJ2 the difference between the boron and sodium
equivalent thicknesses is significant. This difference is consistent
with sodium being retained in the amorphous layer (Houston et al.,
2008; Angeli et al., 2001a, 2008).
The silicon concentration in solution reaches an apparent steady
state quickly (b 15 days) and consequently the equivalent thickness
remains almost constant (Fig. 1, CJ2 and CJ3). In other words, silicon
retention in the amorphous layer increases regularly over time. This
observation is common to both CJ2 and CJ3. In contrast, silicon reaches
steady state more rapidly in CJ8 than in CJ2 and CJ3, and then remains
stable throughout the experimental duration. The equivalent thickness
of silicon is greater than 90 nm in CJ8, which shows that dissolution is
higher than for the other glasses (40 nm for CJ2, 60 nm for CJ3).
Aluminum reaches a maximum within a few days, then begins to
decrease in the case of CJ2. It is important to note that once silicon is
stabilized or has reached steady-state conditions, aluminum starts to
diminish. This behavior has been reported elsewhere (Ribet and Gin,
2004). The concentrations of aluminum and zirconium in solution are
generally below or near the detection limits (Al: 0.01 mg/L; Zr:
0.005 mg/L). In CJ3, aluminum is below the detection limit.
Fig. 2 shows the evolution curve for Si, Al, B, Na and Ca at pH 10 for
CJ2, CJ3 and CJ8 glasses. At pH 10 for CJ2 the equivalent thickness of
boron is less than at pH 7 and 8. In contrast, the equivalent thickness
of silicon exhibits the opposite trend and is higher at pH 10 (Figs. 1
and 2). For example, the equivalent thickness of silicon at pH 10 for
CJ2 is 200 nm, whereas it is 40 nm at pH 7 and pH 8. In CJ3, all
elements except Ca are initially congruent (b30 days), after which
silica and aluminum stabilize. In CJ8, Si, B and Na are congruent until
60 days, when a sudden increase in both B and Na is observed. The
evolution curve of Ca shows that it decreases progressively throughout the reaction.
113
Table 2
Elements in glass and PRI.
Glass
Elements in glass
Elements in PRI
Crystallized secondary phases
CJ2
CJ7
CJ3
CJ4
CJ8
CJ9
Si,
Si,
Si,
Si,
Si,
Si,
Si, Al, Na
Si, Al, Na, Zr
Si, Al, Ca
Si, Al, Ca, Zr
Si (Ca)a
Si, Zr (Ca)a
No
No
No
No
Only at pH 9 and pH 10
Only at pH 10
Al, Na, B
Al, Na, B, Zr
Al, Ca, Na, B
Al, Ca, Na, B, Zr
Ca, Na, B
Ca, Na, B, Zr
a
pH 8 for CJ8 and pH 7-9 for CJ9. Elements retention in the PRI varies with pH. See
the text for more detail.
glass experiments which prevents direct comparison based on altered
glass fractions: same equivalent thicknesses correspond to larger
altered glass fractions if the grains are smaller. Fig. 4 suggests that
glass alteration is highly pH-dependent, and minimum alteration
(b 1%, CJ3) is observed at pH 10. The alteration is very high at pH 7.
This was the case for all the studied glasses except CJ8 and CJ9.
Aluminum-free glasses (CJ8 and CJ9) show high alteration (~50%) at
pH 10 (see equivalent thicknesses for comparison with CJ9).
3.3. Solid characterization
The formation of secondary phases can lead to a resumption of
alteration by dissolution of the amorphous layer. The altered grain
surfaces are therefore observed by SEM (Fig. 5a, b and c); XRD is also
performed when crystallized secondary phases are observed by SEM.
This was the case for CJ8 and CJ9 at pH 10: Fig. 5a and b show SEM
images for CJ8 and CJ9 after 150 days of alteration. As there is no
aluminum in these glasses, the possible crystallized secondary phases
are calcium silicate hydrates (CSH). X-ray diffraction patterns on CJ8
and CJ9 seem to confirm the formation of CSH even if the clear
identification of the precipitated minerals is not possible due to the
large amount of amorphous material in the samples (Fig. 5c).
Moreover, the calculated saturation index confirms solution saturation state with respect to CSH.
4. Discussion
3.2. Effect of glass composition and pH on glass alteration
The experimental results suggest that the glass alteration process
is significantly affected by the glass composition, but these elemental
effects strongly depend on the solution pH. Fig. 3 shows the
equivalent thickness of altered glass, calculated for boron, as a
function of time for different glasses and at various pH values. The
curves show that the glasses behave quite distinctly in the studied pH
range (Fig. 3). Among the glasses, CJ2 exhibits the greatest alteration,
except at pH 10. In CJ2, aluminum is added to the basic three-oxide
composition (Si, B and Na). Substitution of Ca to CJ2 decreases the
degree of alteration significantly at high pH (see CJ3 glass), and
slightly at pH 7. Like Ca, the incorporation of Zr in CJ2 and CJ3 also the
reduces alteration kinetics (see CJ7, CJ4). Nevertheless, glasses CJ2 and
CJ7 show more or less identical properties and are more altered at
pH 7 than at pH 10. Furthermore, comparison of glass pairs e.g. CJ2
and CJ3 (effect of Ca), CJ2 and CJ7 (effect of Zr without Ca), CJ3 and CJ4
(effect of Zr with Ca) clearly reveals that the addition of Ca and Zr
diminishes glass alteration below pH 10. These observations are
consistent with the literature (Gin and Jégou, 2001; Sicard et al., 2004;
Spalla et al., 2004; Angeli et al., 2001a; Cailleteau et al., 2008). CJ8 and
CJ9 show different trends compared to other glasses: at pH 7 to 9 they
initially undergo significant alteration, then the reaction ceases.
However, at pH 10 CJ8 and CJ9 behave differently and show constant
alteration progress, which suggests a specific mechanism.
Fig. 4 shows the altered glass fraction for the longest duration for
five of the six glasses. CJ9 alteration is not included because its specific
surface area and S/V ratio are significantly different from the other
Experimental results demonstrated that the glass alteration
process strongly depends on the glass composition and pH. These
Fig. 6. Na and Ca retention properties at various pH values in the studied glasses.
Alteration duration 150 days, S/V = 2000 m− 1, temperature 90 °C.
114
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
factors influence element retention and diffusion processes in the
amorphous layer, and the formation of crystallized secondary phases.
4.1. Nature of the PRI and crystallized secondary phases
As mentioned earlier, alteration of nuclear waste glasses produces
a PRI and crystallized secondary phases as the main alteration
products. The PRI constituents vary with the glass composition and
pH. Based on the experimental results, elements retained in the PRI of
each test glass are indicated qualitatively in Table 2. Except for
aluminum-free glasses (CJ8 and CJ9) and the highest pH, secondary
phases are not observed in these experiments. Therefore, Table 2
assumes that elements leached congruently with boron (same
equivalent thicknesses) will not be retained in the PRI. For CJ9,
calcium is retained in the PRI for charge compensation of zirconium at
lower pH (7, 8). In the case of CJ8, calcium is not retained at pH 7 and
the PRI is mostly amorphous silica. However, calcium is partly
retained at pH 8 in CJ8 due to the presence of negatively charged
species of silicon. Due to the formation of secondary phases at pH 10
in the aluminum-free glasses, the PRI is mostly amorphous silica (CJ8)
or amorphous silica with zirconium (CJ9).
Alkali (Na) or alkaline-earth (Ca) elements can be retained in the
PRI for charge compensation of Al and Zr (Houston et al., 2008; Angeli
et al., 2001a, 2008). In this study, in order to understand the role of Na
and Ca in charge compensation in the PRI at various pH values,
retention factors were calculated relative to boron (Eq. (5)) and
plotted for the studied glasses (Fig. 6). In CJ2 and CJ7, there is no
calcium in the glass composition and Na is retained in the PRI. Fig. 6
shows that Na retention is close to 30%, the same at pH 7 and pH 8 for
a given glass; there is no retention at pH 10. The opposite is the case
for Ca: calcium is retained more at pH 10 (in the PRI and/or CSH) than
at pH 7. Moreover, Na retention is almost zero or very low when the
glasses contain Ca. It is apparently observed in glasses CJ3, CJ4, CJ8 and
CJ9 (Table 2, Fig. 6). This observation strongly suggests that the PRI
Fig. 7. Equivalent thickness and retention factor of Na and Ca in CJ2 and CJ3 glasses versus time. Alteration duration 300 days, S/V = 2000 m− 1, temperature 90 °C.
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
115
Fig. 8. Boron and silicon equivalent thicknesses versus time for different glasses at various pH values. S/V = 2000 m− 1, temperature 90 °C.
prefers Ca rather than Na. This is well correlated with published
experimental data (Angeli et al., 2006, 2008). Fig. 6 also illustrates that
Ca retention in CJ4 and CJ9 is high at all pH values compared to CJ3 and
CJ8, respectively. The only difference between CJ3 and CJ4 (and
between CJ8 and CJ9) is zirconium (Table 1). This shows that glasses
with zirconium retain more calcium in the PRI (Angeli et al., 2008). In
other words, zirconium enhances the retention of charge compensators in the PRI.
As mentioned earlier, Na is not retained in the PRI at pH 10 (Fig. 6).
At pH 10, KOH is used as a buffer, and K may be retained in the PRI for
charge compensation. In order to verify this assumption, two
experiments were selected (CJ2 and CJ3 at pH 7) and a known
quantity of KCl solution was added to these experiments. Fig. 7
displays the results of leach test experiments. Fig. 7 shows that for CJ2,
Na is congruent with boron after adding KCl. Before adding KCl,
around 25% to 30% of Na is retained in the PRI (Fig. 7c). After adding
KCl, the Na retention factor drops to zero. In CJ3, Na is congruent with
boron and consequently the Na concentration remains unchanged
after adding KCl. However, calcium behaves differently after adding
KCl. Fig. 7d indicates that around 50% to 60% of calcium is retained in
the PRI before adding KCl. After adding KCl, a rapid drop is observed in
Ca retention. These results evidence that PRI may use whatever cation
available in solution depending on its concentration and reactivity.
The PRI probably retains Ca rather than Na for charge compensation.
Fig. 8 can be interpreted considering that the glass alteration is
initially governed by dissolution. Once silicon reaches a steady state
(after about 20 days in most cases), PRI dissolution ceases and the
glass dissolution rate drops by several orders of magnitude. In such
conditions glass alteration remains controlled only by a diffusion
process. This mechanism is clearly observed in CJ2 glass and
dissolution is active for the first 20 days (Fig. 8, CJ2). Conversely, in
the case of CJ9, initial dissolution is fastest at pH 7 and 8, and then the
glass alteration reaction ceases. Alteration of CJ9 strongly suggests
that dissolution is the predominant process that regulates overall
glass alteration and that diffusion through the PRI is very slow.
Previous studies have shown that in CJ8 and CJ9 the PRI formed at
pH 7 and 8 is very protective due to the porosity clogging by efficient
silicon condensation reaction within the PRI because of the absence of
4.2. Influence of pH and glass composition on the diffusion kinetics
Nuclear waste glass alteration is governed by dissolution and
diffusion phenomena (Grambow and Muller, 2001; Rebiscoul et al.,
2004, 2007; Conradt, 2008; Gin et al., 2008; Frugier et al., 2008; Frizon
et al., 2009). Boron is a good diffusion tracer in silicon saturation
conditions. Silicon represents the dissolution front in glass alteration.
Fig. 8 shows how the dissolution and diffusion phenomena drive glass
alteration at various pH. Fig. 8 shows only CJ2 and CJ9, although a
similar trend is observed in other glasses. CJ3, CJ4 and CJ7 behave like
CJ2, while CJ9 represents CJ8.
Fig. 9. Apparent diffusion coefficient calculated for studied glasses at various pH using
boron. Alteration duration 150 days, S/V = 2000 m− 1, temperature 90 °C.
116
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
aluminum (Arab et al., 2008; Jollivet et al., 2008). Arab et al. (2008)
studied the alteration of aluminum-free five-oxide silicate glasses
with varying percentages of zirconium, and characterized the PRI
using SAXS. They reported that the reorganization of PRI can occur
very early, leading to porosity clogging. Likewise, Jollivet et al. (2008)
used 29Si isotopic tracing to investigate gel (PRI) porosity clogging for
the same glasses (Arab et al., 2008) and suggested that porosity
clogging occurs in the external part of the PRI (solution/PRI interface)
after densification of the layer by silicon condensation. In these
studies the glass composition is similar to CJ8 and CJ9, and the
conclusion is consistent with our study. In addition, the CJ9 alteration
curve at pH 10 shows different trends in comparison with pH 7 and
8 (Fig. 8, CJ9). At pH 10, glass alteration is driven by precipitation of
crystallized secondary phases, calcium silicate hydrates (CSH),
followed by renewed alteration (e.g. after 90 days in case of CJ9,
Fig. 8, CJ9) (Gin et al., 2001; Ribet and Gin, 2004). During CSH
precipitation, glass alteration is governed only by dissolution of the
PRI and not by a diffusion process: CSH precipitation decreases the
activities of Si and Ca in solution, just as pure water renewal would,
leading to PRI dissolution to keep these activities high.
Fig. 8 also illustrates that in the studied pH range, high diffusion is
observed at pH 7 followed by pH 8 and 10: the greater the difference
between the equivalent thicknesses of boron and silicon, the more
important the diffusion mechanism in the glass alteration. This
observation is common to all the studied glasses except CJ8 and CJ9,
for which the residual diffusion process is too low to be measurable
whatever the pH.
Fig. 9 shows how the apparent diffusion coefficient of boron varies
with the pH. The diffusion coefficient, DB (see Eq. (6)), is influenced by
the pH, temperature, PRI composition, etc. (Chave et al., 2007). In the
studied glasses, the diffusion coefficient varies from less than 4 × 10−22
to 10−18 m2 s−1. The diffusion coefficient decreases with increasing pH
(Ojovan et al., 2006; Verney-Carron et al., 2010) (Fig. 9). Note that for
CJ9 the value of 4 × 10−22 m2 s−1 was obtained by simply applying
Eq. (6) for comparison with other glass, but it has no real meaning: the
boron equivalent thicknesses minus the silicon equivalent thicknesses
do not follow a square root of time evolution for these two glasses. This
suggests a strong decrease over time of the apparent diffusion
coefficient to an unmeasurable value. In such a case, it makes no sense
to take into account any diffusion process. Nevertheless it is interesting
to know that, should the model remain applicable, the value would be
below 10−24 m2 s−1. Furthermore, the studied glasses can be classified
into 3 pairs: CJ2 and CJ7, CJ3 and CJ4, and CJ8 and CJ9, based on DB. The
only difference within each pair is zirconium. Glasses without
aluminum (CJ8, CJ9) have the lowest diffusion coefficient. A comparison
of CJ2 and CJ3 suggests that incorporating calcium in the glass
composition significantly diminishes the diffusion process. This highlights the roles of aluminum and calcium in glass alteration.
4.3. Influence of the PRI on the solution chemistry
Speciation calculations of all these solutions were carried out with
JCHESS using the chess.tdb database taken from EQ3/6 database for
each glass, pH and sample time (Van der Lee et al., 2003; Wolery,
1992). As solution samples were ultrafiltered to 10000 Da, the
speciation calculation represents only dissolved species in solution.
Fig. 10 shows the activities of SiO2aq and Ca2+, and their relation with
pH when the solution is at equilibrium with the PRI. Fig. 10 indicates
that SiO2aq activity is relatively constant and independent of the pH
below pH 9, followed by a drop at pH 10. At pH 10, silicon activity is
diminished for all the glasses except those without calcium. In CJ8 and
CJ9, SiO2aq can only be stabilized with calcium and significantly
decreases at pH 10.
Fig. 10 also indicates the influences of the glass composition on the
SiO2aq activity. The activity of SiO2aq is the highest for aluminum-free
glasses (CJ8, CJ9). In CJ8 and CJ9, silicon is mostly recondensed as pure
silica below pH 9 (Fig. 11). In other glasses, silicon interacts with Al
and Zr, which reduces silicon activity in solution.
Calcium concentrations are high near neutral pH (7, 8). Calcium
could be congruent with boron but a fraction of calcium is retained in
the PRI for Al and Zr charge compensation. At pH 9 the calcium
activity drops sharply: PRI silicon species have a major role in calcium
condensation. At pH 10 the formation of secondary phases controls
calcium activity. This is also true for CJ8 glass at pH 9 because
secondary phases were observed in the long duration experiments
(Gin and Jégou, 2001).
Saturation indices were calculated for all the glasses in the studied
pH range. The results reveal that the solution is saturated or near
Fig. 10. Activities of SiO2(aq) and Ca2+ versus pH for studied glasses. S/V = 2000 m−1, temperature 90 °C.
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
117
Fig. 12. Saturation index of CSH phase versus pH. S/V = 2000 m−1, temperature 90 °C.
5. Conclusions
The alteration of nuclear waste glasses and silicate minerals is
governed by dissolution and diffusion phenomena. Alteration produces
a silica-rich amorphous layer and sometimes crystallized phases as the
main alteration products. Part of the amorphous layer can be passivating
depending on the alteration conditions (in such cases this material is
known as the passivating reactive interphase (PRI)). Modeling the PRI
composition taking into account the chemical interactions between the
main forming elements (Si, Al, Ca, Zr) is the goal of the present study. For
this purpose the study combines two approaches: experimentation
(this paper) and modeling. Experiments were carried out to understand
the influence of the pH and glass composition on the diffusion
coefficient and glass dissolution kinetics, and to generate data for
model calibration.
Our findings suggest that Si, Al, Ca and Zr have strong interactions
that influence the PRI properties (solubility and diffusivity) and thus
the glass durability.
Fig. 11. Evolution of saturation index of amorphous silica versus time and pH. S/V =
2000 m−1, temperature 90 °C. For pH variations a mean value has been plotted (based on
values at 60, 90 and 150 days.
saturation with respect to amorphous silica and oversaturated with
respect to chalcedony, quartz and other high-temperature silica
phases. Amorphous gel is the only phase observed by solid
characterization methods when the pH is less than 10. Fig. 11 shows
the saturation index of amorphous silica for various glasses with
respect to time and pH. Fig. 11 indicates that CJ8 and CJ9 leachates are
close to saturation whereas CJ7 and CJ2 leachates are undersaturated.
This observation suggests that silicon activity is reduced by aluminum. Neglecting the Al effect when modeling the Si concentrations
would lead to a significant overestimation by a factor of two to five.
At pH 10, secondary phase precipitations were observed for CJ8
and CJ9 glasses, which diminished the saturation state of amorphous
silica in solution. In these glasses the saturation index indicates that
the solution is oversaturated with respect to classical calcium silicate
hydrates available in the data base such as gyrolite, tobermorites
(11 Å, 14 Å, 9 Å), etc. (Fig. 12). CSH stoichiometry and solubility
should be confirmed precisely. Nevertheless oversaturation is consistent with a kinetically limited precipitation. Slight differences are
observed in pH and solution compositions between 10 and 60 days
when alteration renewal is observed on CJ8 at pH 10.
• Al, and to a small extent Zr, have been shown to reduce the Si
activity at saturation: an Al-rich glass will be more resistant to pure
water renewal for this reason alone. Moreover, the lower the Si
activity, the higher the pH required for precipitation of hydrated
calcium silicates.
• Ca interacts mainly with Al and Zr at pH below 8, but starts to
interact with Si above pH 9: CSH are observed to form at pH 10 and
sustain alteration but the most notable phenomenon is a Ca–Si
interaction in the PRI at pH 9. This interaction strongly limits the
calcium activity in solution and sharply decreases the reactive
diffusion coefficient of water and solvated ions within the PRI.
Up to now kinetic models have neglected interactions between
elements such as those discussed in this paper (Grambow and Muller,
2001; Frugier et al., 2009; Verney-Carron et al., 2010). Except for the
last reference, the reason is that such models were applied in media
chemically controlled by glass dissolution, i.e. in a sufficiently narrow
pH range (typically near pH 9 for borosilicate glasses) to be able to
disregard pH-dependant element interactions within the PRI. In case
of Roman archaeological glass, this simplification is acceptable
because the PRI contains 85% of silica (Verney-Carron et al., 2008).
For nuclear and also basaltic glass we think that this simplification
must be revised to improve the models.
Precipitation of crystallized secondary phases that consume elements from the PRI is another phenomenon that must be taken into
account to model and predict the glass durability. Precise modeling of
this phenomena requires a sophisticated PRI model. The next steps of
118
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
this work will be: (1) modeling the PRI composition and diffusivity
within the GRAAL model framework and (2) validating the model for
complex nuclear glass compositions in realistic conditions (e.g.
alteration by groundwater).
References
Advocat, T., Crovisier, J.L., Vernaz, E.Y., Ehret, G., Charpentier, H., 1991. Hydrolysis of
R7T7 nuclear waste glass in dilute media: mechanisms and rate as a function of pH.
Materials Research Society Symposium Proceedings 212, 57–64.
Advocat, T., Jollivet, P., Crovisier, J.L., Del Nero, M., 2001. Long-term alteration
mechanisms in water for SON68 radioactive borosilicate glass. Journal of Nuclear
Materials 298, 55–62.
ANDRA, 2005. Evaluation of the feasibility of a geological repository in an argillaceous
formation. ANDRA report available at http://www.ANDRA.fr.
Angeli, F., Boscarino, D., Gin, S., Della Mea, G., Boizot, B., Petit, J.C., 2001a. Influence of
calcium on sodium aluminosilicate glass leaching behavior. Physics and Chemistry
of Glasses 42, 279–286.
Angeli, F., Charpentier, T., Gin, S., Petit, J.C., 2001b. 17O 3Q-MAS NMR characterization of
a sodium aluminoborosilicate glass and its alteration gel. Chemical Physics Letter
341, 23–28.
Angeli, F., Gaillard, M., Jollivet, P., Charpentier, T., 2006. Influence of glass composition
and alteration solution on leached silicate glass structure: a solid-state NMR
investigation. Geochimica Cosmochimica Acta 70, 2577–2590.
Angeli, F., Charpentier, T., Gaillard, M., Jollivet, P., 2008. Influence of zirconium on the
structure of pristine and leached soda-lime borosilicate glasses: towards a
quantitative approach by 17O MQMAS NMR. Journal of Non-Crystalline Solids
354, 3713–3722.
Arab, M., Cailleteau, C., Angeli, F., Devreux, F., Girard, L., Spalla, O., 2008. Aqueous
alteration of five-oxide silicate glasses: experimental approach and Monte Carlo
modeling. Journal of Non-Crystalline Solids 354 (2–9), 155–161.
Ballou, E.V., Leban, M.I., Wydeven, T., 1973. Solute rejection by porous glass
membranes: III. Reduced silica dissolution and prolonged hyperfiltration service
with feed additives. Journal of Applied Chemistry & Biotechnology 23, 119–130.
Berger, G., Schott, J., Loubet, M., 1987. Fundamental processes controlling the first stage
of alteration of a basalt glass by seawater: an experimental study between 200° and
320 °C. Earth and Planetary Science Letters 84, 431–445.
Berger, G., Claparols, C., Guy, C., Daux, V., 1994. Dissolution rate of a basalt glass in silicarich solutions: implications for long-term alteration. Geochimica Cosmochimica
Acta 58, 4875–4886.
Bickmore, B.R., Nagy, K.L., Gray, A.K., Brinkerhoff, A.R., 2006. The effect of Al(OH)(4)(-)
on the dissolution rate of quartz. Geochimica et Cosmochimica Acta 70 (2), 290–305.
Bildstein, O., Trotignon, L., Pozo, C., Jullien, M., 2007. Modeling glass alteration in an
altered argillaceous environment. Journal of Nuclear Materials 362, 493–501.
Byers, C.D., Jercinovic, M.J., Ewing, R.C., Keil, K., 1985. Basalt glass: an analogue for the
evaluation of the long-term stability of nuclear waste form glasses. Materials
Research Society Symposium Proceedings 84, 67–83.
Cailleteau, C., Angeli, F., Devreux, F., Gin, S., Jestic, J., Jollivet, P., Spalla, O., 2008. Insight
into silicate glass corrosion mechanisms. Nature Materials 7, 978–983.
Chave, T., Frugier, P., Ayral, A., Gin, S., 2007. Solid state diffusion during nuclear glass
residual alteration in solution. Journal of Nuclear Materials 362, 466–473.
Chave T., Frugier P., Gin S., Ayral A., submitted for publication. Glass-water interphase
reactivity with calcium rich solutions, implications for glass long term modeling,
Geochimica et Cosmochimica Acta.
Chou, L., Wollast, R., 1985. Steady-state kinetics and dissolution mechanisms of albite.
American Journal of Science 285, 963–993.
Conradt, R., 2008. Chemical durability of oxide glasses in aqueous solutions: a review.
Journal of the American Ceramic Society 91, 728–735.
Crovisier, J.L., Fritz, B., Grambow, B., Eberhart, J.P., 1985. Dissolution of basaltic glass in
seawater: experiments and thermodynamic modeling. Materials Research Society
Symposium Proceedings 50, 273–280.
Crovisier, J.L., Atassi, H., Daux, V., Honnorez, J., Petit, J.C., Eberhart, J.P., 1989. A new
insight into the nature of the leached layers formed on basaltic glasses in relation to
the choice of constraints for the long term modeling. Materials Research Society
Symposium Proceedings 127, 41–48.
Crovisier, J.L., Honnorez, J., Fritz, B., Petit, J.C., 1992. Dissolution of subglacial basaltic
glasses from Iceland: laboratory study and modeling. Applied Geochemistry (1),
55–81.
Frizon, F., Gin, S., Jégou, C., 2009. Mass transfer phenomena in nuclear waste packages.
In: Wang, Liqiu (Ed.), Advance in Transport Phenomena, vol. 1. Springer Verlag,
Berlin-Heidelberg, pp. 31–133.
Frugier, P., Gin, S., Minet, Y., Chave, T., Bonin, B., Godon, N., Lartigue, J.E., Jollivet, P.,
Ayral, A., De Windt, L., Santarini, G., 2008. SON68 nuclear glass dissolution kinetics:
current state of knowledge and basis of the new GRAAL model. Journal of Nuclear
Materials 380, 8–21.
Frugier, P., Chave, T., Gin, S., Lartigue, J.E., 2009. Application of the GRAAL model to
leaching experiments with SON68 nuclear glass in initially pure water. Journal of
Nuclear Materials 392, 552–567.
Geneste, G., Bouyer, F., Gin, S., 2006. Hydrogen-sodium interdiffusion in borosilicate
glasses investigated from first principles. Journal of Non-Crystalline Solids 352,
3147–3152.
Gin, S., Jégou, C., 2001. Limiting mechanisms of borosilicate glass alteration kinetics:
effect of glass composition. Water-Rock Interaction. A.A. Balkema, Villasimius, Italy,
pp. 279–282.
Gin, S., Ribet, I., Couillard, M., 2001. Role and properties of the gel formed during nuclear
glass alteration: importance of gel formation conditions. Journal of Nuclear
Materials 298, 1–10.
Gin, S., Jégou, C., Frugier, P., Minet, Y., 2008. Theoretical consideration on the AagaardHelgeson rate law to the dissolution of silicate minerals and glasses. Chemical
Geology 255, 14–24.
Gislason, S.R., Veblen, D.R., Livi, K.J.T., 1993. Experimental meteoric water-basalt
interactions: characterization and interpretation of alteration products. Geochimica et Cosmochimica Acta 57, 1459–1471.
Gong, W.L., Wang, L.M., Ewing, R.C., Vernaz, E., Bates, J.K., Ebert, W.L., 1998. Analytical
electron microscopy study of surface layers formed on the French SON68 nuclear
waste glass during vapor hydration at 200 °C. Journal of Nuclear Materials 254,
249–265.
Grambow, B., Muller, R., 2001. First-order dissolution rate law and the role of surface
layers in glass performance assessment. Journal of Nuclear Materials 298, 112–124.
Grambow, B., Jercinovic, M.J., Ewing, R.C., Byers, C.D., 1985. Weathered basalt
hyaloclastites: a natural analogue for the effects of saturation on nuclear waste
glass durability. Materials Research Society Symposium Proceedings 50, 263.
Guy C., 1989. Mécanismes de dissolution des solides dans les conditions hydrothermales déduits du comportement de verres basaltiques et de calcites déformées.
Ph.D. thesis, Université de Toulouse III, France.
Hellmann, R., Penisson, J.M., Hervig, R.L., Thomassin, J.H., Abrioux, M.F., 2003. An
EFTEM/HRTEM high resolution study of the near surface of labradorite feldspar
altered at acid Ph/evidence for interfacial dissolution-reprecipitation. Physics and
Chemistry of Minerals 30, 192–197.
Hellmann, R., Penisson, J.M., Hervig, R.L., Thomassin, J.H., Abrioux, M.F., 2004. Chemical
alteration of feldspar: a comparative study using SIMS and HRTEM/EFTEM. In: Wanty,
R.B., Seal, R.R. (Eds.), Water Rock Interaction. A.A. Balkema, Rotterdam, pp. 753–756.
Hingston, F.J., Raupach, M., 1967. The reaction between monosilicic acid and aluminum
hydroxide: I. Kinetics of adsorption of silicic acid by aluminum hydroxide.
Australian Journal of Soil Research 5, 295–309.
Houston, J.R., Herberg, J.L., Maxwell, R.S., Carroll, S.A., 2008. Association of dissolved
aluminum with silica: connecting molecular structure to surface reactivity using
NMR. Geochimica et Cosmochimica Acta 72, 3326–3337.
Iler, R.K., 1973. Effect of adsorbed alumina on the solubility of amorphous silica in
water. Journal of Colloid and Interface Science 43, 399–408.
Jégou C., 1998. Mise en évidence expérimentale des mécanismes limitant l'altération du
verre R7T7 en milieu aqueux. Critique et proposition d'évolution du formalisme
cinétique. Ph.D. thesis, Université de Montpellier II.
Jégou, C., Gin, S., Larche, F., 2000. Alteration kinetics of a simplified nuclear glass in an
aqueous medium: effects of solution chemistry and of protective gel properties on
diminishing the alteration rate. Journal of Nuclear Materials 280, 216–229.
Jercinovic, M.J., Keil, K., Smith, M.R., Schmitt, R.A., 1990. Alteration of basaltic glasses
from north-central British Columbia, Canada. Geochimica et Cosmochimica Acta 54,
2679–2696.
Jollivet, P., Angeli, F., Cailleteau, C., Devreux, F., Frugier, P., Gin, S., 2008. Investigation of
gel porosity clogging during glass leaching. Journal of Non-Crystalline Solids 354,
4952–4958.
Jones, L.H.P., Handreck, K.A., 1963. Effects of iron and aluminum oxides on silica in
solution in soils. Nature 198, 852–853.
Ledieu, A., Devreux, F., Barboux, P., 2005. The role of aluminum in the durability of
alumino-borosilicate glasses. Physics and Chemistry of Glasses 46, 12–20.
Lee, M.R., Brown, C.L., Hodson, M.E., MacKenzie, M., Hellmann, R., 2007. Characterization of mineral surfaces using FIB and TEM: a case study of naturally-weathered
alkali feldspars. American Mineralogist 92, 1383–1394.
Michaux, L., Mouche, E., Petit, J.C., Fritz, B., 1992. Geochemical modeling of the longterm dissolution behavior of the French nuclear glass R7T7. Applied Geochemistry
Suppl. 1, 41–54.
Munier, I., Grambow, B., Fritz, B., Clement, A., 2004. Modeling the alteration gel composition
of simplified borosilicate glasses by precipitation of an ideal solid solution in
equilibrium with the leachant. Journal of Nuclear Materials 324 (2–3), 97–115.
Oelkers, E.H., Schott, J., 1994. The effect of aluminum, pH, and chemical affinity on the rates
of aluminosilicate dissolution reactions. Geochimica et Cosmochimica Acta 58 (9),
2011–2024.
Ojovan, M.I., Pankov, A., Lee, W.E., 2006. The ion exchange phase in corrosion of nuclear
waste glasses. Journal of Nuclear Materials 358 (1), 57–68.
Rebiscoul, D., Van der Lee, A., Rieutord, F., Né, F., Spalla, O., El-Mensouri, A., Frugier, P.,
Ayral, A., Gin, S., 2004. Morphological evolution of alteration layers formed during
nuclear glass alteration: new evidence of a gel as diffusive barrier. Journal of
Nuclear Materials 326, 9–18.
Rebiscoul, D., Frugier, P., Gin, S., Ayral, A., 2005. Protective properties and dissolution
ability of the gel formed during nuclear glass alteration. Journal of Nuclear
Materials 342, 26–34.
Rebiscoul, D., Rieutord, F., Né, F., Frugier, P., Cubitt, C., Gin, S., 2007. Water penetration
mechanisms in nuclear glasses by X-ray and neutron reflectometry. Journal of NonCrystalline Solids 353, 2221–2230.
Ribet, S., Gin, S., 2004. Role of neoformed phases on the mechanisms controlling the
resumption of SON68 glass alteration in alkaline media. Journal of Nuclear
Materials 324, 152–164.
Samson, S.D., Nagy, K.L., Cotton, W.B., 2005. Transient and quasi-steady-state
dissolution of biotite at 22-25 °C in high pH, sodium, nitrate, and aluminate
solutions. Geochimica et Cosmochimica Acta 69, 399–413.
Scheetz, B.E., Freeborn, W.P.D.K., Anderson, C., Zolensky, M., White, W.B., 1985.
Materials Research Society Symposium Proceedings 44, 129.
Sicard, L., Spalla, O., Barboux, P., 2004. Study of the kinetics of glass alteration by smallangle X-ray scattering. Journal of Physical Chemistry B 108, 7702–7708.
N. Rajmohan et al. / Chemical Geology 279 (2010) 106–119
Spalla, O., Barboux, P., Sicard, L., Lyonnard, S., Bley, F., 2004. Influence of insoluble
elements on the nanostructure of water altered glasses. Journal of Non-Crystalline
Solids 347, 56–68.
Thomassin J.H., 1984. Étude expérimentale de l'altération des verres silicates dans l'eau
douce et en milieu océanique. Apport des techniques d'analyse de surface des
solides. Ph.D. thesis, Universite d'Orléans, France.
Van Bennekom, A.J., Buma, A.G.J., Nolting, R.F., 1991. Dissolved aluminum in the
Weddell-Scotia Confluence and effect of Al on the dissolution kinetics of biogenic
silica. Marine Chemistry 35, 423–434.
Van Cappellen, P., Qiu, L., 1997. Biogenic silica dissolution in sediments of the Southern
Ocean: I. Solubility. Deep-Sea Research II 44, 1109–1128.
Van der Lee, J., De Windt, L., Lagneau, V., Goblet, P., 2003. Module-oriented modeling of
reactive transport with HYTEC. Computers & Geosciences 29 (3), 265–275.
Van Iseghem, P., Aertsens, M., Gin, S., Deneele, D., Grambow, B., McGrail, P., Strachan, D.,
Wicks, G.A., 2007. Critical Evaluation of the Dissolution Mechanisms of High-Level
Waste Glasses. Conditions of Relevance for Geological Disposal (GLAMOR). SCK.
CEN, CEA, Subatech, PNNL, and SRNL. EUR 23097, pp. 1–164.
119
Vernaz, E.Y., Dussossoy, J.L., 1992. Current state of knowledge of nuclear waste glass
corrosion mechanisms: the case of R7T7 glass. Applied Geochemistry 1, 13–22.
Verney-Carron, A., Gin, S., Libourel, G., 2007. Use of natural and archaeological
analogs to validate long-term behavior of HLW glass in geological disposal
conditions. In: Bullen, T.D., Wang, Y. (Eds.), Water-Rock-Interaction. Balkema,
Rotterdam, pp. 659–662.
Verney-Carron, A., Gin, S., Libourel, G., 2008. A fractured Roman glass block altered 1
800 years in seawater: analogy with nuclear waste glass in deep geological
repository. Geochimica et Cosmochimica Acta 72, 5372–5385.
Verney-Carron, A., Gin, S., Frugier, P., Libourel, G., 2010. Long-term modeling of
alteration-transport coupling: application to a fractured Roman glass. Geochimica
et Cosmochimica Acta 74 (8), 2291–2315.
Wolery T.J., 1992. A software package for geochemical modeling of aqueous systems:
package overview and installation guide (version 7.0), Lawrence Livermore
National Laboratory (USA), UCRL-MA-110662 ed., 1992.