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Adsorption / desorption

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Endpoint:
adsorption / desorption, other
Remarks:
partition coefficient
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
see read-across document
Reason / purpose for cross-reference:
read-across source
Radiolabelling:
no
Key result
Phase system:
other: log Kp
Type:
other: log Kp
Value:
3.5
Remarks on result:
other: C12 LAS
Key result
Phase system:
other: log Kp
Type:
other: log Kp
Value:
3.4
Remarks on result:
other: C11.6 LAS
Adsorption and desorption constants:
Kp (C12 LAS): 3210 L/kg (log Kp = 3.5)
Kp (commercial C11.6 LAS mixture): 2,500 L/kg (log Kp = 3.4)
Details on results (Batch equilibrium method):
Sorption equilibrium was achieved rapidly, within 5-10 minutes. Desorption was less pronounced, but still reached rapid equilibration. The sludge-water partition coefficient Kp of 3210 L/kg volatile suspended solids is reported. Applying the same QSAR for the commercial C11.6 LAS mixture results in a value of log Kp = 3.4 (i.e., Kp = 2500 L/kg), consistent with Feijtel et al. 1999 (see section 3.3.1(b)). In the other experiments conducted in this study, only 2-8% was present as dissolved C12 LAS, with the remaining 92-98% adsorbed to the sludge. Despite this high degree of sorption, more than 99% of the LAS load was removed by biodegradation, showing that the adsorbed fraction as well as the soluble fraction of LAS is readily available for biodegradation.
Conclusions:
The log Kp for commercial LAS was 3.4.
Executive summary:

The adsorption-desorption of LAS (read across) in activated sludge was determined in batch experiments. The Kp for commercial LAS was 2,500 L/kg, with a log Kp of 3.4.

Endpoint:
adsorption / desorption: screening
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please see attached read across documentation for complete justification.
Reason / purpose for cross-reference:
read-across source
Type:
Koc
Value:
0.949 L/kg
Remarks on result:
other: Koc estimate from log Kow
Type:
log Koc
Value:
-0.023 L/kg
Remarks on result:
other: Koc estimate from log Kow
Conclusions:
The calculated Koc for MIPA was 0.9494.

Description of key information

The adsorption-desorption of LAS (read across) in activated sludge was determined in batch experiments. The Kp for commercial LAS was 2,500 L/kg, corresponding to a log Kp of 3.4.

The calculated Koc for the second read across substance (MIPA) was 0.949 L/kg.

Key value for chemical safety assessment

Koc at 20 °C:
2 500

Additional information

The adsorption-desorption of LAS (read across) in activated sludge was determined in batch experiments. The Kp for commercial LAS was 2,500 L/kg, corresponding to a log Kp of 3.4. Sorption equilibrium was achieved rapidly, within 5-10 minutes. Desorption was less pronounced, but still reached rapid equilibration. A sludge-water partition coefficient Kp of 3,210 L/kg volatile suspended solids is also reported for C12 LAS (log Kp = 3.5) based on the work of Feijtel et al. (1999). Those researchers found that only 2-8% of commercial LAS was present as dissolved C12 LAS, with the remaining 92-98% adsorbed to the sludge. Despite this high degree of sorption, more than 99% of the LAS load was removed by biodegradation, showing that the adsorbed fraction as well as the soluble fraction of LAS is readily available for biodegradation.

The EPISuite calculated Koc value for the second read across substance (MIPA) was 0.949 L/kg.