7/30/2019 Adsorption of Dl Alanine by Allophane
http://slidepdf.com/reader/full/adsorption-of-dl-alanine-by-allophane 1/6
C l a y M i n e r a l s (1999) 34,233~38
A d s o r p t i o ne f f e c t o f p H
o f D L - a l a n i n e b y
and unit partic le
a l lophane:a g g r e g a t i o n
H. HAS HI ZU ME AND B. K. G. TH EN G *'1
N a t i o n a l I n s t i tu t e f o r R e s e a r c h i n I n o r g a n i c M a te r ia ls ', T s u k u b a 3 0 5 , J a p a n , a n d * L a n d c a r e R e s e a r c h , P r i v a t e B a g
1 1 0 52 , P a l m e r s t o n N o r th , N e w Z e a l a n d
( R e c e i v e d 2 4 F e b r u a r y 1 9 98 ," r e v i s e d 1 5 J u n e 1 9 9 8 )
ABSTRACT: The adsorption of DL-alanine at pH 4, 6 and 8 by a soil allophane has been
determined. Two sets of experiments were carried out: (1) in which the allophane had been kept in a
moist state throughout; and (2) in which the mineral had previously been dried at 50~ In both
instances, the adsorption isotherms showed three distinct regions as the concentration of alanine in
solution was increased: (1) an initial, nearly linear, rise at low equilibrium concentrations; (2) a
levelling off to a plateau at intermediate concentrations; and (3) a steep linear increase at highconcentrations. For comparable concentrations of alanine in solution, adsorption decreased in the
order pH 6 > pH 8 > pH 4. Irrespective of pH, however, more alanine was adsorbed by the 'wet'
allophane than by its 'dry' counterpart. These observations are interpreted in terms of the
morphology and aggregation of allophane unit particles together with the pH-dependent chargecharacteristics of allophane and alanine. The results are compared with published data on the
adsorption of alanine by montmorillonite.
Amino acids as such, or as peptides, or associated
with humic substances (organic matter), occur
widely in soils and sediments (Stevenson, 1982).
The persistence and survival of amino acids in these
environments have been ascribed to adsorption and
physical protection by clays and other fine-grained
mineral constituents (Theng, 1974a; Bada, 1991;
Curry e t a l . , 1994). Clays have also been reported
as being capable of catalysing peptide bond
formation, and of differentiating between the L-
and D-optical isomers of some amino acids (Degens
e t a l . , 1970; Jackson, 1971; Lahav e t a l . , 1978;
Siffert & Naidja, 1992; Bujdak e t a l . , 1996). For all
these reasons, the clay-amino acid interaction has
received a great deal of attention. The focus of
research, however, has been on the adsorption and
intercalation of amino acids by crystalline layer
silicates with pH-independent ('permanent' ) charge,
among which montmorillonite has received much
1 Corresponding author
attention (Theng, 1974a,b; Siffert & Kessaissia,
1978; Dashman & Stotzky, 1982; Hedges & Hare,
1987; Naidja & Huang, 1994).
On the other hand, little is known about the
interactions between amino acids and short-range
order (poorly crystalline) alumino-silicates with
variable charge (e.g. allophane) which seems
surprising as these minerals are widespread in
volcanic ash soils (Wada, 1989; Parfitt, 1990),
and have a large propensity for accumulating and
stabilizing organic matter in soil (Oades e t a l . ,
1989; Theng e t a l . , 1989; Andreux & Theng, 1990).
Although the reactivity of allophane towards
organic compounds, in general, may be ascribed
to the size, shape, and peculiar structure of its unit
particles, the underlying mechanisms are not well
understood (Tate & Theng, 1980; Theng e t a l . ,
1982; Parfitt, 1990). Here we investigate the
adsorption of DL-alanine by a soil allophane from
New Zealand as part of a larger programme of
research on the stabil ization of organic matter in
allophanic soils (Parfitt e t a l . , 1997), and the
possible role of allophane in discriminating
~) 1999 The Mineralogical Society
7/30/2019 Adsorption of Dl Alanine by Allophane
http://slidepdf.com/reader/full/adsorption-of-dl-alanine-by-allophane 2/6
2 3 4 H . H a s h i z u m e a n d B. K . G. T h e n g
b e t w e e n e n a n t i o m e r i c f o r m s o f a m i n o a c id s
( H as h i zu me & T h en g , 1 9 9 6 ) .
M A T E R I A L S A N D M E T H O D S
T h e a l l o p h a n e w a s o b t a i n e d f r o m a s o i l n e a r T e
K u i t i , N e w Z e a l a n d , a n d i s d e r i v e d f r o m t h e
r h y o l i t i c Ro t o e h u t ep h r a , d a t ed a t 4 2 0 0 0 y e a r s
B . P . ( T h e n g e t a l . , 1 9 8 2 ) . T h e f i e l d - mo i s t s o i l w as
s amp l ed f r o m a f r e s h l y ex p o s ed p r o f i l e a t a d ep t h
o f 2 m , a n d t a k e n t o t h e l a b o r a t o ry i n a d o u b l e
p l a s t i c b ag . T h e c l ay ( < 2 g m eq u i v a l en t s p h e r i ca l
d i ame t e r ) f r ac t i o n w as s ep a r a t ed b y d i s p e r s i n g t h e
b u l k s a m p l e i n w a t e r a t p H 3 . 5 w i t h a n u l t r a s o n i c
p r o b e , s e d i m e n t i n g u n d e r g r a v it y , a n d c o a g u l a t i n g
w i t h 1 M N aC1 a t p H 6 . A f t e r d e can t i n g t h e b u l k
s o l u t i o n , t h e c o a g u l a t e d m a t e r i a l w a s d i a l y s e d
a g a i n s t d e i o n i z e d w a t e r u n t i l f r e e o f c h l o r i d e , a n d
s t o r ed a s an aq u eo u s s u s p en s i o n i n a s t o p p e r ed
g l a s s co n t a i n e r . A p o r t i o n o f th i s 'w e t ' a l l o p h an e
w a s d r i e d i n a n o v e n a t 5 0 ~ t o o b t a i n t h e ' d r y '
s amp l e . T h e A 1 /S i r a ti o o f t h e s amp l e , d e r i v ed f r o m
e l e m e n t a l a n a l y s i s o f a n a c i d a m m o n i u m o x a l a t e
ex t r ac t, i s 1 . 57 , w h i l e i ts p o i n t o f z e r o ch a r g e
( P Z C ) , d e t e r m i n e d b y a d s o r p t io n o f N a + a n d C I - , i s
5 . 7 ( T h e n g e t a l . , 1982).
A d s o r p t i o n i s o t h e r ms a t 20 _ + I ~ w e r e d e t e r -
m i n e d b y e q u i l ib r a t i n g t h e ' w e t ' o r ' d r y ' a l l o p h a n e
w i t h 0 . 0 0 6 - 0 . 2 M s o l u t io n s o f a l a n i n e i n st o p p e r ed
p o l y t h e n e t u b e s. R e a g e n t g r a d e a l a n i n e w a s
s u p p l i e d b y W a k o P u r e C h e m i c a l s , J a p an , a n d
u s e d a s r e c e i v ed . T h e s o l u ti o n s w e r e m a d e u p i n
0 . 0 0 4 M N aC1, co n t a i n i n g 1 0 3 M N aN 3 t o i n h i b i t
mi c r o b i a l g r o w t h . I n t h e f i r s t s e t o f ex p e r i men t s w e
u s e d 1 0 0 m g o f ' w e t ' a l l o p h a n e to 1 0 m l o f a l a n i n e
s o l u t io n , w h i l e i n t h e s e c o n d s e t w e a d d e d 2 0 m l o f
s o l u t io n t o 2 0 0 m g o f ' d r y ' a l l o p h a n e . T h e
s u s p e n s i o n s w e r e a d j u s te d t o t h e d e s i r e d p H b y
d r o p w i s e a d d i t io n o f 0 . 1 M H C 1 o r N a O H u s i n g a n
O x f o r d m i c r o p i p e t t e . A f t e r s h a k i n g e n d - o v e r - e n d
f o r 6 6 h , a n d c e n t r i f u g i n g , - t h e c o n c e n t r a t i o n o f
a l a n i n e i n t h e s u p e r n a t a n t w a s m e a s u r e d i n a
S h i m a d z u T O C - 5 0 0 0 a n a l y s er . T h e a m o u n t
a d s o r b e d w a s e s t i m a t e d f r o m t h e d i f f e r e n c e
b e t w e e n t h e a m o u n t i n i t i a l l y a d d e d a n d t h a t
m e a s u r e d a t e q u i l i b r i u m w i t h th e a l l o p h a n e .
R E S U L T S
Fi g u r e 1 s h o w s t h e ad s o r p t i o n i s o t h e r ms f o r t h e
'w e t ' a l l o p h an e ( A w ) , an d F i g . 2 f o r t h e s amp l e t h a t
h a s p r ev i o u s l y b ee n d r ied a t 5 0 ~ ( A d) . I n b o t h
cas e s ad s o r p t i o n d ec r ea s ed i n t h e o r d e r p H 6 > p H
8 > p H 4 . T h e cu r v es a l s o s h o w t h a t ap p r ec i ab l y
m o r e a l a n i n e w a s t a k e n u p b y A w t h a n b y A d a t
c o m p a r a b le v a l u e s o f p H a n d e q u i l i b r iu m c o n c e n -
t r a t i o n . H o w ev e r , a l l t h e i s o t h e r ms a r e s i mi l a r i n
s h ap e h av i n g t h r ee d i s t i n c t r eg i o n s o f ad s o r p t i o n . I n
r eg i o n I ad s o r p t i o n i n c r ea s e s mo r e o r l e s s l i n ea r l y
u p t o a c e r t a i n co n c en t r a t i o n o f a l an i n e i n s o l u t i o n ,
r each es a p l a t eau i n r eg i o n I I , an d s h o w s a s t e ep ,
l i n e a r i n c r e a s e i n r e g i o n I I I . H o w e v e r , t h e l i m i t o f
c o n c e n t r a t i o n to w h i c h e a c h r e g i o n e x t e n d s t e n d s t o
b e w i d e r f o r A w t h an f o r A d . Reg i o n I , f o r ex amp l e ,
r an g e s f r o m 0 t o 0 . 0 3 M f o r A w b u t o n l y f r o m 0 t o
0.01 M for Ad.
3
pH
62
8
"o 1<
4
0
0.1 0.2Equilibrium oncentrationmol/I)
FIG. 1 . I so therms fo r the adsorp t ion o f DL-alan ine by
'w e t ' a l l o p h an e .
1 . 0 I I p H
0.8 ~ 68
0.6 4g
S- 0 . 4
0 . 2
0 , I
0 0.10 0.20
Equilibrium oncentrationmol/I)
FIG. 2 . I so therms fo r the adsorp t ion o f DL -alan ine by
'd ry ' a l lophane .
7/30/2019 Adsorption of Dl Alanine by Allophane
http://slidepdf.com/reader/full/adsorption-of-dl-alanine-by-allophane 3/6
Adsorption of alanine by allophane 235
D I S C U S S I O N
Morphology , charge charac ter i s t i c s , and
a g g r e g a t i o n o f a l l o p h a n e u n i t p a r t i c l e s
Allophane is a collective term for a series of
hydrated alumino-silicates with short-range order,
and an A1/Si ratio typically ranging from 1:1 to 2:1
(Wada, 1989). The primary or un it particle of
allophane is a hollow spherule with an outer diameter
of 3 .5-5.0 nm, and a wall thickness of -0.7 nm.
Aluminium-rich (soil) allophanes apparently have the
imogolite structure over a short range with the
spherule wall being composed of an A1-O,OH
octahedral (gibbsitic) sheet to which orthosilicate
(03 SiOH) groups are attached on the inside (Partqtt,
1990). In Si-rich allophanes, some of the silicate is
polymerized, and a large proportion of the silicate
may be bound to the outside surface of the alumina
octahedral sheet (Wada, 1989; Parfitt, 1990).
Structural defects within the spherule wall give
rise to ~0.3 nm-wide perforations (Wada & Wada,
1977). Theng et al. (1982) have suggested that
(OH)AI(H20) groups, exposed at such defect sites,
are responsible for the variable charge character-
istics of the allophane used here. That is, these
groups can gain protons on the acid side, and lose
protons on the alkaline side, of the PZC (pH 5.7).
In other words, the net surface charge of the
mineral would be positive at pH < PZC, and
negative at pH > PZC.
Rheological measurements suggest that in aqueous
suspensions the unit particles of allophane tend to
form small aggregates through electrostatic and van
der Waals interactions (Wells & Theng, 1985). The
extent of aggregation ( 'flocculation') is close to
maximal at pH 6 when the net surface charge
approaches zero. On the other hand, at pH 8 and pH
4, the particles tend to repel each other, leading to a
reduction in aggregate size. In line with these
suggestions, transmission electron micrographs of
an aqueous suspension at pH -6 of the allophane
used, show hollow spherules with an average
diameter of 4.3 nm, forming 0.030-0.0 35 ~tm
spheroidal aggregates which, in turn, coalesce into
globular clusters of varying size (Hall et al. , 1985).
For spherical particles, the specific surface area,
S (in mZ/g), may be derived from the relationship
S = (6/pD) x 103 (1)
where p is the density (in g/cm3), and D the
diameter (nm), of the particles. Taking a densi ty of
2.6 g/cm3 for allophane, a value of 537 m2/g is
obta ined for the total (external) spherule area, and
66-77 m2/g for the surface area of aggregates.
I s o t h e r m s h a p e a n d a d s o r p t i o n r e g i o n s
For the sake of convenience, we will first
consider the 'wet ' system at pH 6. With an
isoelectric point of 6.11, alanine would exist in
the zwitteri0nic form at this pH. At the same time,
the net surface charge on allophane is essentially
zero. Adsorption would therefore be primarily
controlled by electrostatic interactions involving
the COO and NI-I~ groups of alanine, on the one
hand, and the (OHz)+AI(H20) and (OH)AI(OH)-
groups of allophane, on the other.
We propose that region I of the isotherms
describes adsorption on the external surface of
allophane aggregates, and that the plateau (region
II) indicates full coverage of this surface by alanine
(Fig. 1). Assuming a molecular area of 0.28 nm2 for
alanine, the amount adsorbed at the plateau
(0.42 mmol/g) corresponds to a surface coverage
of 71 m2/g. The good agreement between this value
and the external surface area of allophane
aggregates (66- 77 mZ/g), estimated from electron
micrographs, lends further support to the proposal.
On this basis, it seems reasonable to suppose that
region III of the isotherms represents intra-
aggregate penetration by alanine, followed by
adsorption on surfaces of unit particles making up
an aggregate. Despite the limited data available, the
shape of the isotherms in this region accords with
this interpretation, since a linear increase in uptake
with concentration indicates that fresh sites are
continuously created as adsorption progresses (Giles
et al., 1974a,b). In this case, the process involves
intra-aggregate expansion, possibly accompanied by
some dissociation of uni t particles within aggre-
gates. Linear (C-type) isotherms further suggest
'constant ' partition of solute (here alanine zwitter-
ions) between the bulk and intra-aggregate solution,
terminating in a (second) flat plateau when all the
available (external) spherule surface is occupied by
the solute. The extent of this surface, derived from
equation (1), is 537 m2/g. To achieve complete
surface coverage would require the adsorption of
~3.2 mmol alanine per gram allophane. Since the
concentration of alanine in solution was clearly
insufficient to achieve this level of adsorption
(Fig. 1), no second plateau was observed. Figure 3
gives a schematic representation of the adsorption
process for the three regions of the isotherms.
7/30/2019 Adsorption of Dl Alanine by Allophane
http://slidepdf.com/reader/full/adsorption-of-dl-alanine-by-allophane 4/6
236 H. Hashizume and B. K. G. Theng
The isotherms at pH 8 and pH 4 are similar in
shape to that obtained at pH 6 but s ignificantly less
alanine is adsorbed at comparable concentrations in
so lu t ion . These observa t ions may l a rge ly be
explained in terms of the pH-dependent charge
characteristics of the reactants . At pH 8 both
allophane and alanine have a net negative charge,
while at pH 4 the net charge on both reactants is
posit ive. Because of electrostatic repulsion between
surface and solute, uptake at either pH is less than at
pH 6. The reason for the larger uptake at pH 8 than
at pH 4 is not obvious. However, at pH 8 the
allophane sample has a net negative charge of
20 cmol( ) /kg whereas at pH 4 the net posit ive
charge is 18 cmol(+)/kg (Theng et al. , 1982). It
seems likely, therefore, that charge~zharge repulsion
between allophane unit particles is greater at pH 8
than at pH 4. As a result , the size of allophane
aggregates at pH 8 would be smaller , and the surface
area available for adsorption larger, than at pH 4.
The isotherms for 'dry' allophane ( A d) , a s shown
in Fig. 2, are similar in shape to those observed for
the 'wet ' sample (Aw) as well as showing the same
dependence on pH. However, at comparable equili-
br ium concentrat ion and pH, the capaci ty of A d to
adsorb DL-alanine is appreciably diminished. This
observation is consistent with the structural changes
that drying and dehydration tend to induce. I t is well
known that allophane fails to rehydrate to i ts f ield-
moist s tate after air-drying (Warkentin & Maeda,
1980; Wells & Theng, 1985), while drying at l l0~
causes the aggregates of allophanc to coalesce into a
sheet-like structure (Kitagawa, 1971). Drying at 50~
would therefore be expected to enhance particle-
par t ic le interact ions and aggregat ion, caus ing a
reduction in surface area (Wells & Theng, 1988).
As already proposed, the ammmt adsorbed at the
plateau (region II) represents saturation of the
externa l surface o f allopha ne aggregates (Fig. 3).
For Ad at pH 6, this amount corresponds to a surface
coverage (S) o f -1 7 m2/g. Inserting this value of S in
eqn. (1) gives D - 0.136 ~tm wh ich is a four-fold
increase from the value of 0.030 0035 lam calcu-
lated for the aggregate diameter in Aw (cf. Fig. 1). It
would appear that the size of allophane aggregates
can be subs tant ia lly increased even by mild o ven-
drying (50~ as a result of which the reactivity of
allophane towards organic species is greatly reduced.
Similarly, Ishida (1991) found that prior oven-drying
of allophane-rich soils led to a marked decrease in
their capacity to adsorb polyethylene glycols. On the
basis of s tatis t ical thermodynamics, he was able to
o
Alanine
Equilibrium concentration
FIG. 3. Schem atic illustration of the allop hane-a lanine
interaction in regions 1, lI, and 111 of the adsorption
isotherms.
explain this observation in terms of a reduction in
both the reactivity and extent of the surface that is
accessible to the polymer.
C o m p a r i s o n w i t h m o n t m o r i l l o n i t e
As shown in Figs. 1 and 2, uptake by both Aw
and Ad is maximal at pH 6, close to the isoelectr ic
point (pI ) of a lanine, wi th appreciably less being
adsorbed at pH 4. In marked contrast to allophane,
uptake by m ontmo r i l loni te increases as the med ium
pH fal ls below the pI of the amino acid (Theng,
1974a) . Th i s d i f f e r ence in r eac t iv i ty be tween
a l lophane and montmor i l lon i te may be exp la ined
in terms of the inf luence of pH on the charge
characteristics of the reactants . Unlike allophane,
the negat ive sur face charge o f montmor i l loni te i s
essent ia l ly independent of pH. On the other hand,
amino acids become pos i t ively charged at pH < pI ,
and negat ively charged at pH > pI which in the case
of DL-alanine may be depicted as fol lows:
.H + _HT
C H 3- ~ H - C O O H ~ C H 3- ~ H - C O O ~ - C H 3- ~ H -C O O (2)
NH~ NH~ NH2
+H + +H +
pK t 2,35 pKz 9,87
(cation, acid pH) (zwitterion,near-neutralpH) (anion, alkalinepH)
pH<pI pH=pI=6.11 pH>pl
where K1 and K: are the corresponding equi l ibr ium
constants . Since neutral amino acids, in general,
exist as the corresponding cationic species at low
pH (<pI) , they are s t rongly at t racted to the
7/30/2019 Adsorption of Dl Alanine by Allophane
http://slidepdf.com/reader/full/adsorption-of-dl-alanine-by-allophane 5/6
Adsorp t ion o f a lan ine by a l lophane 237
negatively charged surface of crystalline layer
silicates. The majority of published data on
montmoril lonite (Theng, 1974a,b), therefore, refer
either to adsorption at pH <3 or to uptake by a
hydrogen-saturated clay when cation exchange or
proton transfer is the dominant process.
The adsorption of ~- and 13-alanine by H-
montmoril lonite yielded L-type isotherms, reaching
a plateau at an equilibrium concentration of
~0.02 M (Greenland et a l . , 1965a; Cloos et a l . ,
1966). Although both compounds were apparently
intercalated as the cationic species, the amount
adsorbed at the plateau was appreciably less than
the cation exchange capacity of the clay. For ~- (or
DL-) alanine the plateau adsorption of 0.44 mmol/g
(Greenland et a l . , 1965a) is closely similar to that
shown by 'wet ' allophane at pH 6 (Fig. 1).
However, since the operative mechanism in mont-
moril lonite (dominantly proton transfer) is fund-
amentally different from that in allophane (electro-
static interactions), this similarity is more apparent
than real.
On the other hand, it seems valid to compare
uptake by allophane at pH 6 with that by
montmorillonite at the same pH. In both instances
alanine is adsorbed in the zwitterionic form. As
with allophane, adsorption by Ca-montmorillonite
(at pH 5.6-6.6) up to an equilibrium concentration
of 0.05 M yielded a linear isotherm (Greenland e t
al . , 1965b). This observation was explained in
terms of physical adsorption of alanine by constant
partition between the solution phase and surface-
adsorbed (Stern-layer) water. At the highest
equilibrium concentration of 0.05 M, -0.07 mmol
of alanine was adsorbed per gram of montmorillon-
ite. Even in the absence of intercalation, this
amount is much less than would be required to
saturate the external surface area (106 mZ/g) of the
clay. This would explain why the isotherm did not
level off to a plateau as observed with allophane in
region II (Figs. 1 and 3).
Furthermore, alanine is known to enter the
interlayer space of montmorillonite, forming
single-layer intercalation complexes (Greenland e t
al . , 1965a; Cloos et a l . , 1966). As a result, an extra
(760-106)/2 = 327 m2/g of (interlayer) surface area
would be available for adsorption, assuming a total
area of 760 m2/g for montmorillonite. In other
words, the highest adsorption (0.07 mmol/g)
measured by Greenland et a l . (1965b) was at least
an order of magnitude smaller than what can be
accommodated. In the case of allophane, alanine
began to penetrate the interspherule space when its
concentration in solution (at pH 6) exceeded
-0.075 M (Figs. 1 and 2). Interspherule (or intra-
aggregate) solute penetration in allophane may be
likened to intercalation in montmorillonite since, in
both instances, the process leads to the creation
(exposure) of fresh sites as adsorption progresses,
giving rise to linear isotherms.
CO N CL U SIO N S
The adsorption by allophane of a neutral amino
acid, like DL-alanine, is sensitive to variations in
the pH of the medium as well as to the aggregation
state of the mineral. Adsorption is highest at or near
the isoelectric point (pI) of the amino acid, and
decreases on either side of the pI. Irrespective of
pH, adsorption occurs initia lly on the external
surface of allophane aggregates. When this surface
is completely covered, the organic solute penetrates
the interspherule space within individual aggre-
gates, creating fresh adsorption sites. At comparable
solute concentration and pH, more alanine is
adsorbed by allophane that has been kept moist
than by a pre-dried sample. Even mild drying (at
50~ of allophane appears to enhance partic le-
particle interaction and aggregation, causing a
reduction in surface area and adsorptive capacity.
Neutral amino acids, like alanine, can thus serve as
a probe to assess the extent and mode of interaction
between unit particles of allophane under different
experimental conditions.
ACKNOWLEDGMENTS
Financial support from the Foundation of Research,
Science and Technology to BKGT is gratefully acknowl-
edged. We thank C. Feltham of Landcare Research forassistance with the TOC analysis, and E. Hagenaars of the
same institute for finishing the figures.
REFERENCES
Andreux F. & Theng B.K.G. (1990) Organic sources of
nitrogen and phosphorus nutrients in humus-rich
soils with variable charge. Tran s. 14th Int. Congr.
Soil Sci . , Kyoto, Japan, II,180-185.Bada J.L. (1991) Amino acid eosmogeochemistry. P h i l
Trans. R. Soc. Lond. B333, 349-358.Bujdak J., Eder A., Yongyai Y., Faybikova K. & Rode
B.M. (1996) Investigation on the mechanism of
peptide chain prolongation on montmorillonite. J.
Inorg. Chem. 61, 69-78.
7/30/2019 Adsorption of Dl Alanine by Allophane
http://slidepdf.com/reader/full/adsorption-of-dl-alanine-by-allophane 6/6
2 3 8 H. Hashizume and B. K. G. Theng
Cloos P. , Calicis B., Fripiat J .J . & Makay K. (1966)
Adsorp t ion o f amino-ac ids and pep t ides by mont -
mori l lonite. I . Chemical and X-ray diffract ion s tudies .
Proc. Int. Clay Conf., Jerusalem, I , 2 2 3 - 2 3 2 .
C u r ry G .B . , T h en g B .K .G . & Z h en g H . (1 9 9 4 ) Am i n oacid d i s t r ibu t ion in a loess -pa laeoso l sequence near
Luochuan , Loess P la teau , Ch ina . Org. Geochem. 22,
2 8 7 - 2 9 8 .
Dashman T . & Sto tzky G. (1982) Adsorp t ion and
b i n d i n g o f am i n o ac i d s o n h o m o i o n i c m o n t m o r i l lo n -
i te and k ao l in i te . Soil Biol. Biochem. 1 4, 4 4 7 - 4 5 6 .
Deg en s E .T . , M a t h e j a J . & J ack s o n T .A . (1 9 7 0 )
T em p l a t e ca t a l y s i s : a s y m m et r i c p o l y m er i za t i o n o f
a m i n o a c i d s o n c l a y m i n e r a l s . Nature, 2 2 7 ,
492 493.
Gi les C .H. , Smi th D. & Hui t son A. (1974a) A genera l
t rea tmen t and c lass i f ica t ion o f the so lu te adsorp t ioniso therm. I . Theore t ica l . J. Coll. Interf Sci. 47 ,
7 5 5 - 7 6 5 .
Gi les C .H. , D 'S i lv a A.P . & Ea s ton I .A. (1974b) A
genera l t rea tmen t and c lass i f ica t ion o f the so lu te
adsorption isotherm. II . Experimental interpretat ion.
J. Coll. Interf Sci. 4 7 , 7 6 6 - 7 7 8 .
Green l an d D . J . , L ab y R .H . & Qu i rk J .P . (1 9 6 5 a )
Adsorp t ion o f amino ac ids and pep t ides by mont -
mo ri l lon i te and i l l i te . Par t 1 . Cat ion ex change and
pro ton t rans fer. Trans. Faraday Soc. 61 ,2013 2023 .
Green land D.J . , Laby R.H. & Qui rk J .P . (1965b)
Ad s o rp t io n o f am i n o ac i d s an d p ep t i d e s b y m o n t -mori l lonite and i l l i te. Part 2 . Physical adsorption.
Trans. Faraday Soc. 6 1 , 2 0 2 4 -2 0 3 5 .
Ha l l P i . , C h u rch m an G . J. & T h en g B .K .G . (19 85 ) S i ze
d is t r ibu t ion o f a l lophane un i t par t ic les in aqueous
suspensions. Clays Clay Miner. 3 3 , 3 4 5 -3 4 9 .
Hash izume H. & Theng B.K.G. (1996) Can a l lophane
d i s c r i m i n a t e b e t ween o p t i ca l is o m ers o f am i n o
acids? Sapporo Conf Chem. Clays" Clav Miner.
1 1 9 - 1 2 0 .
Hedges J . I . & Hare P .E . (1987) Amino ac id adsorp t ion
b y c l ay m i n e ra l s i n d i s t i l l ed wa t e r . Geochim.
Cosmochim. Acta, 5 1 , 2 5 5 - 2 5 9 .Ish ida T . (1991) Effec t o f o rgan ic mat ter and a l lophane
o n ad s o rp t io n o f p o l y e t h y l en e g l y co ls o n t o s o m e
soils. Aust. J Soil Res. 29, 515 525.
Jackson T .A. (1971) Preferen t ia l po lymeriza t ion and
ad s o rp t i o n o f L -o p t i ca l i s o m ers o f am i n o ac i d s
re la t ive to D-op t ica l i somers on kao l in i te t empla tes .
Chem. Geol. 7 , 2 9 5 - 3 0 6 .
Ki tagaw a Y. (1971) The 'un i t par t ic le ' o f a l lophane . Am.
Miner. 5 6, 4 6 5 - 4 7 5 .
L ah av N . , W h i t e D . & C h an g S . (1 9 7 8 ) P ep t i d e
fo rmat ion in the p reb io t ic e ra : thermal condensa t ion
of g lyc ine in f luc tua t ing c lay env i ronments . Science,2 0 1 , 6 7 -6 9 .
Na i d j a A . & Hu an g P .M . (1 9 9 4 ) As p a rc t i c a c i d
i n t e r ac t i o n w i t h C a -m o n t m o r i l l o n i t e : ad s o rp t i o n ,
desorption and thermal s tabi l i ty . Appl. Clay Sci. 9,
2 6 5 - 2 8 1 .
O a d e s J . M . , G i l l m a n G . P . & U e h a r a G . ( 1 9 8 9 )
In terac t ions o f so i l o rgan ic mat ter and var iab le-
charge c lays . Pp . 69 95 in : Dynamics of Soil
Organic Matter in Tropical Ecosystems (D .C .C o l e m a n , J . M . O a d e s & G . U e h a r a , e d i t o r s ) .
N i f r A L P r o je c t, U n i v e rs i ty o f H a w a i i .
P a r f i tt R .L . (19 90 ) A l l o p h an e i n Ne w Z ea l an d - - A
rev i ew . Aust. J. Soil Res. 2 8 , 3 4 3 - 3 6 0 .
Parf i t t R .L . , Theng B.K.G. , Whi t ton J .S . & Shepherd
T .G. (1997) Effec t s o f c lay minera l s and land use on
organ ic mat ter poo ls . Geoderma, 7 5 , 1 -1 2 .
Si f fer t B . & Kessa i ss ia S . (1978) Con t r ibu t ion au
m ecan i s m e d ' ad s o rp t i o n d e s ~ -am i n o -ac i d e s p a r l a
montmori l lon i te . Clay Miner. 1 3 , 2 5 5 -2 7 0 .
Si f fer t B . & N aid ja A. (1992) S tereose lec t iv i ty o f
montmori l lon i te in the adsorp t ion and deaminat ionof some amino ac ids . Clay Miner. 27, 109 118.
Stevenson F .J . (1982) Humus Chemistry: Genesis,
Composition, Reactions. W i l e y , N e w Y o r k.
Tate K.R. & Theng B.K.G. (1980) Organ ic mat ter and
its interact ion s with inorga nic soi l consti tuents. Pp.
2 2 5 - 2 4 9 i n : Soils with Variable Charge (B .K .G .
Theng , ed i to r ). Ne w Zealand Socie ty o f So i l Sc ience ,
L o w er Hu t t.
Then g B.K.G. (1974a) C om plexes o f c lay minera l s wi th
am ino ac ids and pep t ides . Chem. Erde, 3 3 , 1 2 5 -1 4 4 .
Theng B.K.G. (1974b) The Chemistry of Clay-Organic
Reactions. Ad am Hi l g e r , L o n d o n .Theng B.K.G. , Russe l l M. , Churchman G.J . & Parf i t t
R .L . (1982) Surface p roper t ies o f a l lophane , ha l loy-
si te, and imogoli te. Clays Clay Miner. 3 0 , 1 4 3 -1 4 9 .
Y h e n g B . K . G . , Y a t e K . R . & S o l l i n s P . ( 1 9 8 9 )
Cons t i tuen ts o f o rgan ic mat ter in tempe ra te and
t rop ica l so i l s . Pp . 5 -32 in : Dynamics of Soil Organic
Matter in Tropical Ecosystems ( D . C . C o l e m a n ,
J .M.Oades & G. Uehara , ed i to rs ) . Ni tTAL Pro jec t ,
Un i v e r s i t y o f Haw a i i.
W a d a K . ( 1 9 8 9 ) A l l o p h a n e a n d im o g o l i t e . P p .
1 0 5 1 -1 0 8 7 i n : Minerals in Soil Environments, 2nd
edit ion (J .B. Dixon & S.B. Weed, edi tors). Soil
S c i en ce S o c i e t y o f Am er i ca , M ad i s o n, W i s co n s i n.
Wada S.-I . & Wada K. (1977) Density and structure of
a l lophane . Clay Miner. 1 2 , 2 8 9 -2 9 8 .
Warken t in B.P . & Maeda T . (1980) Phys ica l and
m e c h a n i c a l c h a r a c t e r i s t ic s o f A n d i s o l s . P p .
2 8 1 - 3 0 1 i n : Soils with Variable Charge (B.K.G.
Theng , ed i to r ). Ne w Zea land So cie ty o f So i l Sc ience ,
Lower Hut t .
W el l s N. & The ng B.K.G. (1985) Fac to rs a f fec t ing the
f low behav iour o f so i l a l lophane suspens ions under
low shear rates . J. Coll. lnterf Sci. 1 0 4 , 3 9 8 -4 0 8 .
W e l l s N . & T h e n g B . K . G . ( 1 9 8 8 ) T h e c r a c k i n g
behav iour o f a l lophane- and fer r ihydr i te - r ich mate-
r ia l s; e f fec t o f p re t rea tmen t and mater ia l am end-
ments . Appl. Clay Sci. 3 , 2 3 7 - 2 5 2 .
Top Related