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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Under the test conditions, Coco fatty acids 2-sulfoethyl ester, sodium salt demonstrated a low to moderate tendency to adsorb to sludge. Koc values determined according to OPPTS 835.1110 of 1412 and 1490 L/kg were observed for two STP sludges. The average value of 1451 L/kg is used for risk assessment purposes. Based on this Koc a Kd soil and sediment is calculated by EUSES of 29 and 72.5 L/kg respectively. The soil and (suspended) sediment-water partition coefficient is calculated to be 43.7 and 37.2 m3/m3.

Key value for chemical safety assessment

Koc at 20 °C:
1 451

Other adsorption coefficients

Type:
log Kp (solids-water in suspended matter)
Value in L/kg:
2.162
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in soil)
Value in L/kg:
1.463
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in sediment)
Value in L/kg:
1.861
at the temperature of:
20 °C

Additional information

The adsorption-desorption of Sodium lauroyl Isethionate which is the main component of Coco fatty acids 2-sulfoethyl ester, sodium salt

was determined for two STP sludges according to OPPTS guideline 835.1110.

The sludges were taken from waste water treatment plants treating predominantly domestic waste water. Adsorption and desorption isotherms were determined over a concentration range from approximately 0.007 to 0.7 mg/L. The adsorption-desorption experiments were performed under sterile conditions at 20°C ± 2°C in the dark on a roller mixer at a sludge: 0.01 M CaCI2 solution ratio of 1:250.

Adsorption equilibrium in sludge was reached after 3 hours. Desorption equilibrium was also reached after 3 hours. Sodium lauroyl Isethionate was shown to be stable under sterile conditions.

Sodium lauroyl isethionate adsorption and desorption isotherms could be described by the Freundlich equation. Freundlich adsorption and desorption coefficients are summarised in the table below.

Test System

%OC

KF,ocads

(cm3/g)

KF,ocdes

(cm3/g)

Sludge

41.0

1412

1780

Maaskant Sludge

43.0

1490

1842

Based on the observed Koc values it can be concluded that under the test conditions Coco fatty acids 2-sulfoethyl ester, sodium salt demonstrated a low to moderate tendency to adsorb to the two sludges.

[LogKoc: 3.16]