Adsorption of several herbicides by montmorillonite, kaolinite and illite clays

0045-6535/78/0401--0365~02o00/0

Chemosphere No. 4, PP 365 - 370, 1978. © P e r g a m o n Press Ltd. l ~ i n f e d in Orea'~ Brifain.

ADSORPTION

OF SEVERAL

HERBICIDES AND

BY

ILLITE

Martine TERCE, Station de Science du Sol - I. N . R . A . (Received in France 20 ~ r c h T h e r e are m a n y cult to p r o p o s e s o m e

1978;

MONTMORILLONITE,

KAOLINITE

CLAYS

R.

-Route

CALVET de St Cyr, Versailles - F R A N C E

received in UK for public~%ion 6 April

1978)

publications on clay-herbicide interactions but it is nevertheless diffi-

general rules to describe adsorption o w i n g to the great variability of the \

published data (except for c h a r g e d molecules,

such as paraquat).

Bibliographic studies s h o w

that m o n t m o r i l l o n i t e s have b e e n extensively

studied relative to other clays for w h i c h the follo-

w i n g publications are noteworthy : H A M A K E R

et al (1966) I, W E B E R

NAMARA

and TOTH

and W E E D

(1970) 3 . This lack of k n o w l e d g e leaves u n a n s w e r e d

(1968) z and M a c

several questions con-

cerning the part played by different clays in the soil. It is, therefore, desirable to p r o p o s e s o m e general conclusions on the adsorption of herbicides by clay adsorbants. T h e p u r p o s e of this p a p e r is to present e x p e r i m e n t a l results on the adsorption of several herbicides by an illite, a m o n t m o r i l l o n i t e and a kaolinite and to p r o p o s e s o m e solutions to the p r o b l e m s I - MATERIALS A

AND

e n c o u n t e r e d in this field of research.

METHODS

- Herbicides.

Nine herbicides are studied : Atrazine :2-chloro-4- e t h y l a m i n o triazine,

tentative

Terbutryne

: Z-Methylthio-4-Ethylamino-6-tert.-butylamino-

benzthiazuron : N - ( Z - b e n z o t h i a z o l y l ) - N - M e t h y l - N ' - m e t h y l u r e a , methoxyphenyl)-N,

N-dimethylurea,

-6-isopropylamino-l,?~ 5 i, 3, 5 triazine, M e t h a -

Metoxuron

: N'-(3-chloro-4-

Chlortoluron : N ' - ( 3 - c h l o r o - 4 - m e t h y l p h e n y l )

thylurea, Isoproturon : N'-(4-isopropylphenyl) 3, 5, 6-trichloropicolinic acid, P y r a z o n

- N, N - d i m e t h y l u r e a ,

Pieloram

- N, N - d i m e -

: 4 - amino

: l-phenyl-4-amino-5-chloro-pyridazone,

Napropamide:

N, N -diethyl-Z- (I -naphtalenyloxy)-napr o p a n a m i d e .

Products were

supplied by C I B A G E I G Y , PR OCIDA.

BASF,

BAYER,

RP

Phytosanitaire,

SANDOZ,

This w o r k w a s s p o n s o r e d by Ministate de la Culture et de l']~nvironnement ( F R A N C E ) .

365

-

366

Jo. 4

B - Clays. The clays used are a kaolinite calcium perties

from

Provins

saturated of t h e s e

a montmorillonite

and an illite from

fraction

less

clays are

from

Greece

(TERCE,

CALVET,

Le Puy in Velay (TESSIER,

1974) 4

1 9 7 5 ) 5 . T h e C1- f r e e ,

t h a n Z ~ of e a c h c l a y i s u s e d t h r o u g h o u t

this study.

Some pro-

g i v e n i n t a b l e I. Table I

Montmorillonite

Total s ~r fa_~e Area m g

813

Internal surface Z -1 Area m g

766

External surface 2 -1 Area m g C.E.C. meq/100

g

Chemical composition of b a s a l s u r f a c e

C - Adsorptxon

suspensions adjusted were case,

were were

made always

were

ranging

less

5 to 25

The suspensions centrifuged

at Z0°C.

228 nm (chlortohron),

63

130

104

18

Z7

hydroxyls

w i t h 25 m l of a q u e o u s

oxygene

to g e t v a l u e s

herbicide

and chlortoluron

of m i n e r a l .

than the herbicide

500 m g

for which adsorption

The maximum

solubilities.

solution.

concentrations

in the

T h e p H of t h e s u s p e n s i o n s

of 3, 4. 5, 6. 5 a n d 8. A d s o r p t i o n

(pH 3) a n d f i v e i n i t i a l c o n c e n t r a t i o n s

were

are

isotherms

used in each

~g/cm 3_

were

stirred

The supernatant

at : ZZZ-3 n m ( a t r a z ine),

mixed

with one gramme

in an acid medium

from

58

i n t h e c a s e of n a p r o p a m i d e

with exther HCI or NaOH

determined

130

measurements.

used except

measurement

II!ite

63

oxygene

25 m l o f c l a y s u s p e n s i o n of clay w e r e

Kaolinite

a t 20 ° C i n a t h e r m o s t a t e d solutions

ZZ5 n m ( t e r b u t r y n ) , 241 n m ( i s o p r o t u r o n ) ,

were

analyzed

agitator

f o r 24 h o u r s

by UV s p e c t r o m e t r y

Z44 n m ( m e t o x u r o n ) , ZZ4 n m ( p i c l o r a m ) ,

and then

absorption,

ZZ6 n m ( m e t h a b e n z t h i a z u r o n ~ 228 nm (pyrazon),

Z16 n m

No. 4

367

(napropamide). II - E X P E R I M E N T A L

RESULTS

T h e a m o u n t s of a d s o r b e d h e r b i c i d e at t h r e e pH v a l u e s a r e g i v e n in t a b l e II. Three substituted ureas

(chlortoluron,

isoproturon,

w h a t e v e r the pH o r the c l a y . F o r the o t h e r h e r b i c i d e s - Montmorillonite~ picloram

the a d s o r p t i o n d e c r e a s e s

Illite

with terbutryn,

in the o r d e r :

napropamide,

and p y r a z o n

- Montmorillonite> - lllit~

Kaolinite>

m e t o x u r o n ) a r e not a d s o r b e d

I11ite~ Kaolinite

Montmorillonite>

Kaolinite

with atrazine with methabenzthiazuron.

The r e s u l t s a l s o s h o w t h a t a d s o r p t i o n i n c r e a s e s

w i t h the m e d i u m a c i d i t y .

T a b l e II A m o u n t s of h e r b i c i d e

a d s o r b e d at d i f f e r e n t pH ( ~ m o l e g - I )

Montmorillonite Herbicides pH pH (initial concentration in the suspension) 2~ 8 - 3 6,5 Atrazine (0, 093 p m / c m 3) Z,8 0

pH 8

Kaolinite pH pH Z, 8 - 3 6,5

0

Terbutryn ( 0 , 0 4 5 ] ~ m / c m 3)

4,3

0,7

Methabenzthia zuron (0, 113 } ~ m / c m 3 )

3,3

0

0

Napr opamide _ (0, 091 p m / c m 5)

1,0

0,4

0,4

Pyrazon (0, 11Z } ~ m / c m 3)

0,8

Picloram (0, 112 } ~ m / c m 3) Phenyl ureas

0

0

Illite pH ~m 8

- 3

pH 6, 5

0,7

3,30

2,2

2,9

5,1

Z,5 0

0

0

Adsorption isotherms in acid conditions (pH.~3) m a y be described by a Freundlich type relation : Q = K C e I/n w h e r e

Q = Amount

adsorbed/unit m a s s of adsorbant

C e = Equilibrium concentration K and I/n = constants.

The v a l u e s of K and I / n a r e g i v e n in t a b l e III.

368,

Igo. 4

T a b l e III Characteristics

of a d s o r p t i o n i s o t h e r m ~ i n a c i d m e d i a . V a l u e s of Q i n u M / c m ~ a n d C e i n ~ M / c m 3.

Terbutryn

87 000

calculated

i

K

1/n

12 000

1/n O, 345

K 1,6

-

1,61

for values

Illite

Kaolinite

Montmorillonite 1/n K 0,78 2-0

Atrazine

of K w e r e

1,60

480

1, 16

L

Methabenzthiazuron

138

Napropamide

1, 10

56

Pyrazon

9

N D

1, 7

-

1,35

-

Picloram

L N D

of t e r b u t r y n

is very

great

N D

20

Adsorption

N D

compared

1

-

to the adsorption

of o t h e r h e r b i c i d e s .

Ill - DISCUSSION A - The main

parameters

The experimental the molecular the medium

properties

have allowed the three

of h e r b i c i d e s ,

properties

The molecular the dipolar

following parameters

the physico-chemical

properties

to b e v a r i e d :

of t h e a d s o r b a n t s

and

Among

( p K a = 4, 3),

or less

atrazine

c u l t to p r e d i c t

involved in adsorption

and polarizability

ionized

at pH values

of h e r b i c i d e

surface

properties

are

different

organic

molecules

may be variable.

crystal

essentially either

the ionizacoordination

bonds.

t h a n 3.

These

from

which allow are terbutryn

this point,

it i s d i f f i -

on clay s u r f a c e s .

structures

and chemical

as a consequence,

W h i l e it i s e a s y to p r e d i c t

very difficult to forecast

constants

of c l a y s u r f a c e s

( s e e t a b l e I) a n d ,

bonds and hydrogen

have ionization

( p K a = 3, 5). A p a r t

molecules

properties

clays have different

three

e q u a l to o r g r e a t e r

( p K a = 1, 67) a n d p i c l o r a m

the behaviour

The three

as coordination

are

a s w e l l a s t h e a b i l i t y to f o r m

used in this study,

b - The physico-chemical

on the contrary,

phenomena

bonds.

the molecules

to be m o r e

of h e r b i c i d e s

properties

character

bonds or hydrogen

them

conditions

acidity.

a - Molecular

bility,

of a d s o r p t i o n _

the characteristics

composition.

their

Their

a b i l i t y to a d s o r b

ion exchange

behaviours,

of o t h e r k i n d s of i n t e r a c t i o n s

it i s , such

369

~lo. 4

c - Medium

acidity.

Two phenomena is increased

:

t a k e p l a c e w h e n t h e a c i d i t y of a n h e r b i c i d e - c l a y

- ionization

of the herbicide

- aluminization variations

of the s u r f a c e

account

(TERGE,

system

molecules

of t h e c l a y ( M I L L E R ,

1965) 6 , J A C K S O N

(1960) 7 ) which produces

properties.

Since aluminum herbicides

suspension

and aluminum

CALVET,

hydroxides

1977 ; C A L V E T .

play an important TERCE,

p a r t in the a d s o r p t i o n

1977) 8 ' 9 i t

is necessary

of

to t a k e i n t o

the e f f e c t of the acidity on the clay adsorb a nt. B - Clay-herbicide

interactions.

a - Ionic bonds. These

are likely

all the molecules For

are anionic

the two triazines

of a tra z i n e

to b e p r e s e n t

a t pH v a l u e s

the adsorption

molecules

with picloram,

is closely

is also maximum

related

by several

ted adsorption

an ion exchange

sating

to

- either

molecules

are

authors

organic

w o u l d be e x p e c t e d .

Thus,

1966 , BAILEY,

protonated

the f o r m e r ,

A t p H v a l u e of Z, 9,

of i o n i z e d m o l e c u l e s .

(WEBBER,

between

protonated_

For

6~

it c a n b e s e e n i n This conclusion

1 9 6 8 ) 10' 12 w h o a t t r i b u -

molecules

and compa-

cations, - or a protonation

surfaces

(MORTLAND, b - Other Polar

description organic

in acid conditions.

to t h e n u m b e r

has been given previously

and terbutryn.

o f 6, 5 a n d 8 s o t h a t n o a d s o r p t i o n

a n d 96 ~ of t e r b u t r y n

t a b l e II t h a t a d s o r p t i o n

atrazine

water

1 9 7 5 ) 1Z'

d u e to t h e h y d r a t i o n

water

on clay

13

may exist but the experimental

Due to aluminization,

through

coordination

the surface

aluminum

bonds as has been supposed TERCE,

results cations

do not a l l o w any can interact

for the adsorption

with

of m e t h a -

1 9 7 7 ) 9 . T h i s k i n d of b o n d i s a l s o p o s s i b l e

and pyrazon.

Hydrogen

(CALVET,

forces

b y A1 a n d F e c l a y s ( C A L V E T ,

with napropamide

-

TERCE,

molecules

bonds.

and non-polar

molecules

benzthiazuron

1968 ; C A L V E T ,

possible

to b e g i v e n .

of the organic

bonds are equally molecules

TERCE,

possible

on clay surface.

1 9 7 5 ) 13 .

with : This was described

for atrazine

adsorbed

onAl-clay

No. 4

370

-

surface h y d r o x y l groups of kaolinite as have b e e n p r o p o s e d for the adsorption of

picloram (CHEUNG,

1973) 14 .

IV - C O N C L U S I O N M o n t m o r i l l o n i t e has, generally, a greater adsorption capacity than kaolinite and illite, but adsorption is a l w a y s very small in neutral m e d i u m .

T h r o u g h aluminization,

lies the clay properties and has a very great effect on adsorption_ played by the ionization of molecules, picloram,

O w i n g to the d o m i n a n t part

it is possible to a p p r o x i m a t e l y describe the adsorption of

atrazine and terbutryn in acid m e d i a _

one is limited to hypothesis

the acidity m o d i

F o r other conditions, and for other herbicides,

pertinent to the adsorption m e c h a n i s m s

f r o m a q u e o u s solutions.

Finally, no clear relations b e t w e e n adsorption and clay properties (surface area, C . E . C . . . ) can be proposed. T h e nature of the present results and the great variability of published results strongly indicate that adsorption is probably m a i n l y due to surface impurities such as A 1 or F e oxy-hydrc> xides. A s a consequence,

it a p p e a r s that the description of herbicide adsorption by clays depends

on the possibility of characterizing these impurities_

Further,

it m a y

be postulated that the clay

content of a soil, b a s e d on a g r a n u l o m e t r i c analysis, is nearly a l w a y s of no use in the study and description of adsorption. REFERENCES I. H A M A K E R

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