Differential thermal analysis as an indicative method for the determination of soil mineral demage.

Thermochimica Acta, 83 (1985) 107-112 Elsevier Science Publishers B.V., Amsterdam

Differential method

-Printed

thermal

107

in The Netherlands

analysis

for the determination

as an indicative of soil mineral

demage. IrGger._ .PY and Smykatz-bless.%. ineralogy,l!niversity

Tnst.

of

!Karlsruhe,Uest-Germany Abstract:A zation This

'QTA method

of clay

is done

tures

is oullined

mineral

by determination

of the dehydroxylation

is compared

with

x-ray

between

illitic

mineral

structures

the presented

clays

which

structures

of the peak effect

were

of illites

strongly

db,struction.

and the temperaas tiell.The method

exoeri:ortal

acids

showed

affected

is very suitable

the characteri-

oartial

areas

diffractometry.The and different

method

enables

and their

interaction

t?et the clay

by these

scics

to characteri:<

and that

tr;sse oro-

cesses. 1ntroduction:Clay minerals in soils and fine grainec sri_'i-ents _-__________ are responsible for the fixation of water and dissolved icns. These

alumosilikates

are characterized by sheet structureslsim34of Sir4 Octahedra'Lith water tetrahedra an!J AlCb

plified:layers and

some additional

interlayer

water

large

surface

moved

easily

growth The

of these

in the interlayer

the attack

lutions

may weaken

of polluted

by the

as well,can of the soils

method

be reand the

and intensity by the

another

(Cnl)

study

this

possibility

these

may have

minerals

and acid

is to elucidate

or thermal

forest

interdependence

between

of interferences

to characterize

a simple

soils,

damages.

structures

analytical

so-

structures

of the abundant

of observed

a

structures.

of clay mineral

interferences(compare

dis0rdcr.G enerally

solutions

of clay mineral

and size

to a lot of

them.Among

mineral

clay

of pollution

to the degree

djffractograms

observed

between

aim of this

ethod: The defect character _______ determined by I eans ,,l x-ray defects

of clay

for the disorder

for the degree

and its correlation

sensitive

destroy

or aggressivk,(acid)

to the stability

is studied.The

and by this

are very

or partly

the interaction

: ,d indicative

tural

particles

to the fertility

of clay minerals

influence

In this paper

offers

spaces.‘cth,the

cations,adsorbcd

of plants.

processes,which

x-ray

,as other

fine grained

to contribute

structures

large

cations

and cations

may be

methods.in structural

will

be mainly

with fig.Z).DTA thl- degree

clay I;jincrals include

of struc-

I'H,sometimos

108 additional

water,t.oo.The dehydration of ill:

po:ation

by the defect

dereases.Thus

starts

resp.dehydroxylation(=eva-

of clay minerals

character:with

dehydroxylation

disorder

behaviour

increasing

earlier,and

the correlation

is strongly

degree

for the

Solutions

in

determination

soils.-?

n

of

order

results,it

is necessary

conditions

of differential

the

of structural

may offer

abundance

of

under

and compar

strongly

analysis.(Table

thermal

a suitable

conta,,inated

to get reproduc;ble

to investigato

the

of this reaction

the degree

and the dehydroxylation-behawiour

method

of disorder

the intensity

between

influenced

ble

standardized

l,compare

with

Smykatz,1974).

Table 'i:conditions of differential thermal analysis -___________________~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ lO;/min heating rate amount

100 mg

of sample

Pt/Pt,Rh

thermocouples inert mater.

n12C'3

furnace

air

atm.

ceramic

crucibles The dehydroxylation chemical ter-in

of clay

composition,the

the temperature

minerals

on the

state and i.he I>- ,- ,I Ji c: :lr i'-

structural range

appears-dependent

between

450 and

C(Table

800

2)

Table

2:Dehydroxylation temperatures of main clay mineral types -___^_______________~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ mineral group formula --__________________~~~~~~~~~ int~sl~Y~fn~34e'____~~~~~~~~:~~~~:__

1 aolinte

Al ((OH) Si o 4 25 2

Illite

530-580

-

I(0 7A12((: i-t:.2A10 3Si3 71‘,,0 . . .

Fe-Chlorite

_

520-6C?

Fe-l g-Silicates

'g-Al-Chlorite

550-623

Pg-Al-"

600-660

-___________________-Vermiculite

Pg-Al-Silicates

4~2r

480-550

Fe-Smectite

Fe-Al-Silicates

nH 2 o-

450-520

ntl c 700-600 Al-i'g-Silicates 2 ixed layer Fe-1'g_Al " varable 500-700 _______ ____________________________I___________~~~~~.~~~~~~~~ Al-Smectite

Illites

are the predominant

Therefore Illites

the present

are ,!ot swelling

course,they

may include

ral state,but atYPa

being

some primary

undisturbed

soils

and

sediments.

with this main clay

and show relative

in case of abundant

ralativly

in

clay minerals

--tudy concerns

stable

differences

series

in the structu-

of illites

by external

type.

structures.1 f

which

include

influences,tho

109 application

In standardized tion

effect

onset

area

3T analyses

may be done

temperatures)

determination metric

i,ethod should

of the outlined

be possible.

the determination

by measuring

of the dehydroxyla-

thl: temperatures(peak

and the areas. It was found

's weight

measurement

method,bu'> there

determination

is more

is a good

(Figure

that the oeak area

exact

correlation

and

than the plani-

between

both kinds&

1).

Figure 1:Correlation of an area(cm')and its weightLmg) ,,,,,_,,__,_,,_,,__,,,,_,,,,,,__,--'-,-,~~~~~-~ -- - Aelotlo”

between

on.3 ~-

The

best

transperent

The used different

under

samples

defect

the clays

were

peak

three

were

and onset

decreasing destruction It emerges

being

contacted

x-ray

behaviour

temperatures

2-5 summarize

structural

disorder,

of the treated and peak

by acids

experiments

a)thh.re is a significant

,H25[ ,), for ten days

the obtained

diffractograms

show a clear

results dercrea-

the ool-interference t0o.i.igure 3 repre:-llites.Generally,

area as well decrease

acidity) .The deLailed

of the illites these

experi-

C) and investigated.

Figures

pH(=increasing

from

obtained

acids(e.g.HCl.H:"3

2) and a broadl)ning of the peaks

the thermal

the peak

in the same manncr.The

of the size of all interferences(e.g.for

see Figure sents

prepared

of the illites

with

dried(SO-80

area is to transfer

cut out the cont:ir8::and to weight.

always

pH conditions.After

Results:The following ------of the experiments.The sing

the peak

characters

by the contact

different

lmgl

paper,to were

1

Oreo Id

weM$t

way to characterize

to a heavy

mentally

115

can be seen

effects

with

of partial

in Figures

4 and 5.

that

correlation

between

pH and degree

of

110

Elntlun "nkschedlrher Suuren ?,"I d,e Sf.b,l,l., "0"llllfen

Figure

w

2:Descreasing

OOP-interference material

DTA-Verhalten sauregeschtidlgter lllite

536

‘560

542

Figure3:Thermal

behaviour

of acid treated

of illitic

in different

and changing

-TI’cI

illites.

of the

pi-l.

acids

111

70

1

0.5

I

1

r

I *

I.5

2.5

I 3

3s

1 L

1

L.5

IPHI

.O'

Figure

4,:Area(weight various

in mg)of

acids

with

in correlat .ion to

a 3TA-picture

decreasing

OP.

[‘Cl 570-

560 -

550-

S‘O-

530

520 -

510 -

500 -

‘90

*

FigureS:

I L.5

1.

I 3.5

I 3

2.5

9TA temperature with

I 2

I 1.5

I 1

I

0.5

of neak,maximu.,

I

IPHI

.O'

and onset,

o= behaviour

in HCJ,superior

line

x=‘ behaviour

in HP.OJ

+=behaviour

in H2SI'i,inferior

line.

112 b)the

effect

uf acid aggression

is different

for the used

acids,

in that way:HClciJF!T'3-zt!2SG4! c)the

pH of2.5

structural

shows

to be a critical

stability

is weakened

At this pH of 2.5 the amount solutions

increased

structure release

became

the Flack even

Forest

show pH-values

!\cknowledqment:we _-___

from

the

delivering

of

clay

that

regions

between in

are grateful

which

the

in the contacted out,that

the crystal

it was possible

to

ions.

lower(Rli.imel,P’rtiger,Smykatz

_________

for

destroyed

of soil waters

found

,so pointing

a lot of the incorporated

Investigations

below

evidently.

of cations

considera>l:

as largely

value

in the Kraichgau

and

2.5 and 4,in extreme

to the companies

material,and

to

““5~s

Fuchs

and Didier

B.?etzal

for the

photos. Lit *Smykatz-K1oss.W -__"

.:Differential and results

cases

preparation!.

Thermal

Analysis.Application

in Pineralogy.-K.Springer-

Verlag,Heidelbcrg(1974)