malmö, abm meeting may 2012 publication of the abm ringtest studies on cec and exchangeable cations...

Malmö, ABM meeting May 2012

Publication of the ABM ringtest studies onCEC and exchangeable cations

Dohrmann, R. BGR/LBEG


2 papers were accepted by Clays and Clay Minerals:

Interlaboratory CEC and exchangeable cation study of bentonite buffer materials: I. Cu(II)-triethylenetetramine method

Interlaboratory CEC and exchangeable cation study of bentonite buffer materials: II. Alternative methods

Dohrmann, R., Genske, D., Karnland, O., Kaufhold, S., Kiviranta, L., Olsson, S., Plötze, M., Sandén, T., Sellin, P., Svensson, D., Valter, M.

BGR/LBEG, S&B Industrial Minerals, Clay Technology, B+Tech, ETH Zürich, SKB


Motivation and questions

• Large differences of results reported during 2010 meeting

• Lab exchange of data to clarify:– How large is scattering (precision)?– Which results are more plausible (accuracy)?


What is a real difference?TR-09-29 (LOT) Svensson, 2010 (ABM meeting)

Mg2+ analysis of the same ABM samples differed between different labs

Mg2+ meq/100 g lab A lab BCalcigel 8.7 14.6MX80 3.6 8.6Rockle 9.7 17.2DepCAN 15.2 24.9Ikosorb 16.6 26.6…

Mg2+ a few meq/100 g

larger at contact


I. Cu-trien method


5 labs participated, Cu-trien details

water buffer %/Cu-trien max possible elemental Lab . (M) (mL) (mL) (mL) bentonite COX adsorbed (max.) CEC (meq/100 g) analysisLab 1 0.015 10 25 - ≈ 60 % ≈ 145 ICPLab 2 0.015 20 50 - ≈ 60 % ≈ 145 ICPLab 3-1 (setup1) 0.01 10 50 - 83% 107 AASLab 3-2 (setup1) 0.01 20 40 - 42% 213 AASLab 4 0.02 5 44 1 130-140 500 58% 152 AASLab 5 0.01 10 50 - 80+120 200+300 50%+34% 177 (120 mg) ICP

Cu-trien

200400 ± 50

200

sample mass (mg)

200

Lab technique 1 time (min) technique 2 time (min) technique 3 time (min)Lab 1 hand-shaking 15 sonication 10 rocking platform 30Lab 2 vibrating table 120 vibrating table 30Lab 3-1 shaker 120Lab 3-2 shaker 120Lab 4 sonication 3 30 times end-over, manuallyLab 5 end-over-end shaking 120

before Cu-trien addition after Cu-trien addition


Exchange population, precision (1)

Ca2+ data inaccurate, but partly with good precision

Ca2+ data inaccurate, but partly with good precision

exchangeable cation MX80 COX Dep. CAN ASHApopulationNa+/CEC (VIS) (%) 70 24 27 73K+/CEC (VIS) (%) 2 16 2 1Mg2+/CEC (VIS) (%) 8 32 30 16Ca2+/CEC (VIS) (%) 36 170 66 24control sum (%) 116 242 125 114

MX80 COX Dep. CAN ASHA

Na+ 58.4 2.6 22.3 63.3standard deviation 2.1 0.4 1.6 2.3

K+ 1.8 1.7 1.6 0.5standard deviation 0.4 0.2 0.3 0.2

Mg2+ 6.9 3.4 24.3 13.8standard deviation 0.5 0.4 0.7 0.6

Ca2+ 29.9 18.5 54.2 20.6standard deviation 1.1 4.6 2.1 0.4

CEC (VIS) 83.9 10.9 82.2 86.5standard deviation 1.5 0.7 1.9 2.1

CEC (ICP/AAS) 84.8 12.1 82.6 86.3standard deviation 3.9 2.8 3.8 3.7


Precision (standard deviation)

bentonites

COX

0.0

1.0

2.0

3.0

4.0

5.0

stan

dard

dev

iatio

n (m

eq/1

00 g

)

NaK Mg

CE

C (

VIS

)

CE

C (

ICP

/AA

S)

Ca


Conclusions Cu-trien

• The overall quality of the returned CEC results using Cu-trien method was good

• Some outliers were detected

• Exchange population (cations) exceeds CEC largely

• The most important question what is a real difference? can be evaluated based on ‚precision data‘ now


II. Alternative methods

without COX


Details of alternative methods

Cu-trien'5xcalcite'

Lab (mL) n (mg)Lab 1 0.50 *) ⅓ of 25 3 500 ICPLab 2 0.15 *) ⅓ of 50 3 800±50 ICPLab 4 1.0 25 6 100 KjeldahlLab 5 0.01 50 1 400+600 ICP*) the total volume used was 25 mL respectively 50 mL, which was added in three portions of approximately equal volume

(M)elemental analysis

NH4Ac NH4Clrepetitions sample mass

Lab technique 1 time (min) technique 2 time (min) technique 3 time (min)

Lab 1 hand-shaking 10sonication (homogenizer probe)

1.5 rocking platform 30

Lab 2sonication (ultrasonic bath)

15 vibrating table 120

Lab 4 end-over-end shaking 1.) 1000; 2.-5.) short Lab 5 end-over-end shaking 120

dispersion after index cation addition


Exchange populationexchangeable cation MX80 Dep. CAN ASHApopulation

Na+/CEC (%) 69 27 67K+/CEC (%) 2 2 1Mg2+/CEC (%) 8 27 15Ca2+/CEC (%) (all labs) 26 49 20control sum (%) 105 105 103

Na+/CEC (%) 69 27 67K+/CEC (%) 2 2 1Mg2+/CEC (%) 8 27 15Ca2+/CEC (%) (all) 20Ca2+/CEC (%) (only lab 2 and 5) 24 46control sum (%) 103 102 103

only most plausible Ca 2+ results

results of all labs


Accuracy?

*: inflated by chloride-rich pore water; **: inflated by sulphate-rich pore water (gypsum dissolution); ***: questionable if inflated by dolomite dissolution.

MX80 Dep. CAN ASHA

Na+ 58.8 *22.4 *60.8standard deviation 1.4 1.2 3.9

K+ 1.7 1.7 0.5standard deviation 0.1 0.2 0.1

Mg2+ 6.7 */***22.8 *13.4standard deviation 0.8 1.5 0.8

Ca2+ **20.2 **/***38.8 **18.6standard deviation 1.6 1.4 0.8

CEC 84.6 83.9 90.8standard deviation 2.1 0.5 3.3


Conclusions alternative methods

• Precision of alternative methods is good

• Accuracy is partly not attainable, here more information than just CEC analyses are needed

• K+ and CEC results are (mostly) accurate

• Na+, Mg2+, and Ca2+ results partly inflated by chloride- or sulphate-rich pore water and soluble phases


Thank you


What is a real difference?

• If lab A and lab B use the same method:– result A result B: good precision (± small deviation)– result A result B (difference > precision): individual error(s) note: check with standard clay

• If lab A and lab B use different methods:– result A result B: indication for good precision– result A result B (difference > precision): option 1) individual error(s) option 2) systematic difference = operationally correct (both?) option 3) „complicated minerals“ such as zeolites (specific

adsorption) or vermiculites (slow / incomplete cation exchange)


What is an accurate/precise CEC result?

0

20

40

60

80

100

120

different CEC methods

CE

C (

meq

/100

g)

Reuverton (BGR/LBEG standard)

Ag

TU

(m

od

)

Am

mo

niu

m a

ceta

te

bar

ium

ch

lori

de

Cu

-tri

en

Co

-Hex

amin

e

Ag

TU

cal

cite

Cu

-tri

en c

alci

te

Co

Hex

cal

cite

Cu

-tri

en 5

xcal

cite

0

20

40

60

80

100

120

different CEC methods

CE

C (

meq

/100

g)

ammonium acetate, 0.5 g and 2 g

barium chloride, 0.5 g

barium chloride, 2 g

calcareous hectorite (CMS source clay)

Compensation of two sources of error, occasionally good agreement


Example for good precision, single lab (38 bentonites)

y = 1.00 x - 0.0

R2 = 0.994

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70

Cu-trien5xCc 1. series

Cu

-tri

en

5x

Cc

re

pe

titi

on

Na y = 1.00 x + 0.0

R2 = 0.987

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0.0 1.0 2.0 3.0 4.0 5.0 6.0


Cu

-tri

en

5x

Cc

re

pe

titi

on

Ky = 0.99 x - 0.1

R2 = 0.9997

0

10

20

30

40

50

0 10 20 30 40 50


Cu

-tri

en

5x

Cc

re

pe

titi

on

Mg

y = 1.00 x - 0.5

R2 = 0.998

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60 70 80


Cu

-tri

en

5x

Cc

re

pe

titi

on

Cay = 0.98 x + 0.4

R2 = 0.979

0

20

40

60

80

100

120

0 20 40 60 80 100 120


Cu

-tri

en

5x

Cc

re

pe

titi

on

sumy = 0.98 x + 0.9

R2 = 0.987

0

20

40

60

80

100

120

0 20 40 60 80 100 120


Cu

-tri

en

5x

Cc

re

pe

titi

on

CEC


exch

ange

able

catio

n po

pula

tion

(%)

Na+ K+ Mg2+ Ca2+ control Ca2+ (*) control

MX80 Dep.CAN ASHA

sum sum (*)

exch

ange

able

catio

n po

pula

tion

(%)

Na+ K+ Mg2+ Ca2+ control Ca2+ (*) control

MX80 Dep.CAN ASHA

sum sum (*)

malmö, abm meeting may 2012 publication of the abm ringtest studies on cec and exchangeable cations...

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