Comparative Laboratory Leaching Test Methods to Study Post
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Transcript Comparative Laboratory Leaching Test Methods to Study Post
Comparative Laboratory Leaching Test
Methods to Study Post-Treatment
Storage Period Impacts on CCA
Leachability and Fixation in Treated
Kempas (Koompassia malaccensis)
Heartwood
Andrew Wong and Lai Huat Choi
Faculty of Resource Science & Technology,
University Malaysia Sarawak (UNIMAS),
Kota Samarahan,
Sarawak, Malaysia
INTRODUCTION
CCA Preservatives
CCA preservatives is one of the most
effective wood protecting chemical for many
years
Environment issues of CCA components
leaching in the media - lead to restrictions
of CCA application.
Many countries have even switched to
organic-based preservative
Laboratory leaching test studies
– some concerns
Need to devise suitable harmonise leaching test
methods for comparison of biocide risk
assessments between labs leaching test
But also need to have a lab leaching test that is
realistic to actual environmental exposures of
wood preservatives - trying to relate lab results to
the “real world” - the extent of rainfall and other
climatic effects between regions
EN84 leaching test may be too severe for natural
non-aquatic exposures of treated wood
Any prospects for a relatively milder lab leaching
test system?
Aim of Study
Compare 3 laboratory leaching test
methods (denoted as: EN84, EN84-1 and
EN84-2, severe to mild leaching).
Leachability of CCA in heartwood of freshly
treated Kempas (Koompassia
malaccensis).
To determine if CCA leaching from kempas
is arrested with longer storage fixation
periods.
MATERIALS & METHODS
Wood Material Preparation
Preservative treatment and conditioning
14-days laboratory leaching tests
Elemental analysis of leachates
Data analysis
Wood Material Preparation
Timber species:
-Kempas …permeable heartwood
(Koompassia malaccensis)
Structural-used Malaysian hardwood (roof truss,
utility poles)
Air dried wood block samples (20 x 20 x 20
mm) cut from sawn timber
Test blocks end-grain sealed with Nippon
paint and conditioned at 1050C, 48 hours,
and weighed oven dry (g) before CCA
treatment
Preservative Treatment & Storage Periods
Replicated Kempas wood blocks impregnated
with Type C CCA-salt to target uptake retention
of 5.6 kg/m3
30 min
2 hr
Initial vacuum
(1 kgf/cm2)
Pressure
(14 kgf/cm2)
Freshly treated wood stored for periods of 0 day,
2 days, 1 week, 2 weeks & 4 weeks at ambient
temperature
Laboratory Leaching Tests
Test
EN84
EN84-1
Initial Vacuum
Impregnation?
Yes (30 min)
No
Initial Dipping
in Water?
No
Yes
Leaching
Periods
Immersion in
Water
Water
Change?
EN84-2
2 weeks
24 hours
2, 24, 48, 72,
96 hr and
every 48 hr
24, 48, 72, 96
hr and every
48 hr
Only 5 hr
daily
Daily
CCA Component Analysis in Leachates
Cu & Cr determined by FAAS
As determined using AAS EDL Lamp
system
Component losses expressed in µg/ml
Cumulative leaching losses (µg/ml) for
each of Cu, Cr & As over the leaching
test duration
RESULTS
Cumulative Cu leaching (µg/ml) by 3 lab. methods
EN84
EN84-1
5
4
3
2
1
5
Cu Leaching (ppm)
Cu Leaching (ppm)
Cu Leaching (ppm)
5
EN84-2
4
3
2
1
0
0
0
50 100 150 200 250 300 350
4
3
2
1
0
0
50 100 150 200 250 300 350
Hours
Hours
Hours
4 Weeks
2 Weeks
2 Days
0 Day
0 50 100 150 200 250 300 350
1 Week
Cumulative Cr leaching (µg/ml) by 3 lab. methods
EN84-1
EN84-2
6
6
5
5
5
4
3
2
1
0
Cr Leaching (ppm)
6
Cr Leaching (ppm)
Cr Leaching (ppm)
EN84
4
3
2
1
3
2
1
0
0
0 50 100 150 200 250 300 350
4
0
50 100 150 200 250 300 350
Hours
2 Weeks
2 Days
0 Day
50 100 150 200 250 300 350
Hours
Hours
4 Weeks
0
1 Week
Cumulative As leaching (µg/ml) by 3 lab. methods
EN84-1
5
EN84-2
4
3
2
1
0
0 50 100 150 200 250 300 350
As Leaching (ppm)
5
As Leaching (ppm)
As Leaching (ppm)
EN84
4
3
2
1
0
0
50 100 150 200 250 300 350
5
4
3
2
1
0
0 50 100 150 200 250 300 350
Hours
Hours
4 Weeks
2 Weeks
2 Days
0 Day
1Week
Hours
Cumulative plot for leaching of Cu (ppm) among 3
leaching methods
0 day
2 days
1 wk
EN84
EN84-1
EN84-2
2 wk
4 wk
Cumulative plot for leaching of Cr (ppm) among 3
leaching methods
0 day
2 days
1 wk
EN84
EN84-1
EN84-2
2 wk
4 wk
Cumulative plot for leaching of As (ppm) among 3
leaching methods
0 day
2 days
1 wk
EN84
EN84-1
EN84-2
2 wk
4 wk
Table: Total Leaching (µg/ml) of CCA Components for Menggris by
EN84, EN84-1 & EN84-2 Methods
Fixation periods
Leaching
methods
4 wk
EN84
4 wk
Cu
Cr
As
-----------------(µg/ml)----------------1.1 abcde
1.6 ab
1.4 bcd
EN84-1
0.7 abc
1.7 ab
0.9 ab
4 wk
EN84-2
0.5 a
0.6 a
0.5 a
2 wk
EN84
1.5 de
2.1 b
1.8 cd
2 wk
EN84-1
0.9 abcd
1.8 ab
1.1 bc
2 wk
EN84-2
0.7 ab
0.6 a
0.5 a
1 wk
EN84
1.7 e
1.5 ab
2.0 d
1 wk
EN84-1
1.5 de
2.1 b
1.8 cd
1 wk
EN84-2
0.7 abc
0.7 a
0.5 a
2 days
EN84
1.4 bcde
1.6 ab
1.6 cd
2 days
EN84-1
1.8 e
2.0 ab
2.1 d
2 days
EN84-2
1.4 cd
1.2 ab
0.9 ab
0 day
EN84
2.6 f
3.7 c
3.1 e
0 day
EN84-1
2.4 f
4.7 cd
2.9 e
0 day
EN84-2
4.0 g
5.8 d
4.0 f
• Within- column values sharing the same letter do not differ significantly (multiple comparisons)
CONCLUSIONS
Among the CCA components for the 3
laboratory leaching tests, the order of
leaching severity was: Cr > As > Cu.
EN84-2 method gave expectedly milder
leaching than EN84 and EN84-1.
No significant difference (P<0.05) in CCA
leachability between methods EN84 and
EN84-1
Wood blocks (4 wk fixation / EN84-2
method) showed the lowest CCA
components leaching.
Obviously, wood blocks (0 day fixation /
EN84-2 method) showed the highest CCA
components leaching.
Overall increasing storage period improves
CCA fixation (reduces leachability) but
does not appear to completely fix CCA on
to Kempas heartwood
ACKNOWLEDGEMENT
Unimas Fundamental Research Grant
Unimas Postgraduate Fellowship for H.C.Lai
Mr Nigel Lim from Sarawak Forestry
Corporation
IUFRO SAP partial travel support donated by
Korea Forest Research Institute (FRFI)
THANK YOU!