Benzenesulfonic acid, 4-C10-13-sec-alkyl derivs., ammonium salts

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption, other

Remarks:

Batch Equilibrium

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Peer-reviewed research publication

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
Refer to Section 13.2 for read-across justification.

Qualifier:

no guideline followed

Principles of method if other than guideline:

A sorption-isotherm and the kinetics of adsorption and desorption of LAS to activated sludge were determined in batch experiments. Three different biodegradation tests were also carried out (an OECD 301F ready biodegradation test; a batch activated sludge [BAS] test; and a "by-pass" test developed to mimic condition of the pilot scale activated sludge plant).

GLP compliance:

no

Type of method:

batch equilibrium method

Media:

sewage sludge

Test temperature:

Not reported

Analytical monitoring:

yes

Details on sampling:

At least every other day 24-h samples of 2.5L influent and 2.5L effluent were collected in PE bottles and total (sum of adsorbed and dissolved) LAS concentrations were determined using an HPLC method adapted from Feijtel et al. 1995. At least once a day 200 mL grab samples were taken from the aeration tank and return sludge and transferred into PE centrifuge tubes for determination of dissolved and absorbed LAS. The sludge samples were immediately centrifuged for 15 min at 3500 rpm. The supernatant was transferred into PE bottles and preserved by 3% formalin and stored for a maximum of 10 days at 4°C until further analysis. Representative aliquots of pre-settled influent, final effluent, or supernatant of the centrifuged sludge samples were passed over 6 mL preconditioned C18 SPE columns at a rate not exceeding 10 mL/min. The SPE columns were washed with 2 mL methanol/water and eluted with 5 mL of methanol. The eluate was then passed through strong anion exchange (SAX) columns, washed, eluted and subsequently evaporated to dryness under a gentle flow of nitrogen gas. The dry residue was dissolved in 2-5 mL of HPLC mobile phase.

Details on matrix:

Monitoring data were collected in a pilot-scale municipal activated sludge treatment plant. The plant consisted of a completely mixed aeration tank (490L) and a secondary settler (280L). The plant was operated at C12 LAS influent concentrations between 2 and 12 mg/L and at sludge retention times of 10 and 27 days.

Details on test conditions:

A sorption-isotherm and the kinetics of adsorption and desorption of LAS to activated sludge were determined in batch experiments. Three different biodegradation tests were also carried out (an OECD 301F ready biodegradation test; a batch activated sludge [BAS] test; and a by-pass test developed to mimic condition of the pilot scale activated sludge plant). Only the sorption results are presented here.

Key result

Type:

Koc

Value:

2 500 L/kg

Remarks on result:

other:

Remarks:

C11.6 LAS (commercial LAS)

Key result

Phase system:

solids-water in effluent sewage sludge

Type:

Kp

Value:

3 210 L/kg

Remarks on result:

other: C12 LAS

Key result

Phase system:

solids-water in effluent sewage sludge

Type:

Kp

Value:

2 500 L/kg

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. 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.

Validity criteria fulfilled:

not applicable

Conclusions:

The log Kp for commercial LAS was 3.4.

Executive summary:

The adsorption-desorption of LAS 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.

Reference 2

Endpoint:

adsorption / desorption, other

Remarks:

Batch Equilibrium

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
Refer to Section 13.2 for read-across justification document.

Reason / purpose for cross-reference:

read-across source

Key result

Type:

Koc

Value:

2 500 L/kg

Remarks on result:

other: read-across from commercial LAS (C11.6 LAS)

Key result

Phase system:

solids-water in effluent sewage sludge

Type:

Kp

Value:

2 500 L/kg

Remarks on result:

other:

Remarks:

read-across from commercial LAS (C11.6 LAS)

Validity criteria fulfilled:

not applicable

Conclusions:

The adsorption-desorption of the test item in activated sludge was determined in batch experiments. The Kp was 2,500 L/kg, with a log Kp of 3.4.

Executive summary:

In a one-to-one read-across approach, the substance benzenesulfonic acid, 4-C10-13-sec-alkyl derivs. (source substance) is considered appropriate for direct read-across (one-to-one) to Benzenesulfonic acid, 4-C10-13-sec-alkyl derivs., ammonium salts (target substance) for the endpoint adsorption/desorption. In conclusion, the adsorption-desorption of the test item in activated sludge was determined in batch experiments. The Kp was 2,500 L/kg, with a log Kp of 3.4. A full justification for the read-across approach is presented in IUCLID Section 13.2.

Reference 3

Endpoint:

adsorption / desorption, other

Remarks:

adsorption/desorption

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Well-documented journal article.

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
Refer to Section 13.2 for read-across justification document.

Qualifier:

no guideline followed

Principles of method if other than guideline:

A study of the kinetics and equilibrium of LAS adsorption/desorption was performed to determine the best fit model using a batch equilibrium method. Details on the method used are given below.

GLP compliance:

no

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

no

Test temperature:

20 degrees C

Analytical monitoring:

yes

Details on sampling:

- Concentrations:
For adsorption/desorption kinetics: 100 mg/L
For equilibrium isotherms: 5, 7, 10, 15, 20, 30, 50, 60, 80, 100, 150, 180, 200, 250, 300, 400, 500, 600, 700, 750, 800, 850, 900, 950, 1000, 1200, 1400, 1600, and 1800 mg/L
For adsorption kinetics: 2, 5, 8, 15, and 30 min; 1, 2, 3, 10, 24, 36, 49, and 61 hrs.
For desorption kinetics: 2, 5, 8, 15, and 30 min; 1, 2, 3, 6, 10, 24, 34, and 48 hrs.
For adsorption equilibrium isotherms: 24 hrs
For desorption equilibrium isotherms: 24 hrs

Details on matrix:

COLLECTION AND STORAGE
- Geographic location: Granada Basin, Spain
- Sampling depth (cm): first 25 cm
- Storage conditions: room temperature
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): air-dried, ground, 2 mm sieved

Details on test conditions:

TEST SYSTEM
- Amount of soil/sediment/sludge and water per treatment (if simulation test): 2.5 g soil
- Soil/sediment/sludge-water ratio (if simulation test): 0.125 soil/solution
- Number of reaction vessels/concentration: duplicate
Adsorption kinetics: 2.5 g soil was mixed with 20 mL of LAS solution, and shaken for a specified amount of time. The samples were then centrifuged for 15 min at 5000 rpm. The supernatent was then analysed using LC-MS/MS. A blank sample was also made to determine the adsorption onto the tubes and degradation during the study.
Desorption kinetics: 2.5 g soil was mixed with 20 mL of 100 mg/L LAS solution. After shaking for 24 hrs, the solution was centrifuged for 15 min at 5000 rpm. Liquid phase was removed, and 20 mL of water added. The samples were centrifuged again for 15 min at 5000 rpm, and the supernatent analyased.
Adsorption isotherms: 2.5 g soil was mixed with 20 mL of LAS solution, and shaken for 24 hrs. The samples were then centrifuged for 15 min at 5000 rpm. The supernatent was then analysed using LC-MS/MS.
Desorption isotherms: 20 mL of water was added to the remaining solid phase. After shaking for 24 hrs, the solution was centrifuged for 15 min at 5000 rpm.
- Are the residues from the adsorption phase used for desorption: Yes (desorption isotherms)

Computational methods:

The adsorption of LAS consists of two different processes, and initial fast-adsorption process as the LAS adsorbs to the macro-pores in the soil (process 1), and a second slow adsorption process as the LAS adsorbs into micro-pores in the soil (process 2). For the kinetic studies, the experimental data was modeled using a pseudo-first order kinetic model.

For adsorption: q=_(i=1)^(i=2)q_(e,i) (1-e^(-k_(i^t ) )) where i referes to the process (1 or 2), and q is the adsorption capacity of the soil, and q_e is the adsorption capacity of the soil at equilibrium.

For desorption: q^*=_(i=1)^(i=2)q^*_(e,i) (1-e^(-k_(i^t ) )) where i referes to the process (1 or 2), and q* is the desorption capacity of the soil, and q*_e is the desorption capacity of the soil at equilibrium.

The adsorption/desorption of LAS was experimentally determined and fitted to a Langmuir/quadratic isotherm model: q_e=(q_(max,L)*K_L*C_e)/(1+K_l*C_e )+ (q_(max,Q)*C_e (b_1+2b_2*C_e))/(1+b_1*C_e+b_2*C_e^2 ) where q_e is the soil adsorption capacity at equilibrium, L refers to Langmuir terms, and Q refers to quadratic terms, q_max is the saturation capacity of the adsorbent, K_L is the Langmuir coefficient, C_e is the adsorbate concentration in liquid phase, and b_1 and b_2 are quadratic coefficients.

The macro-pore adsorption rate increased with increased carbon chain length (process 1), while the micro-pore adsorption rate increased with decreasing carbon chain length (process 2). The total percentage of LAS adsorbed increased with increasing carbon chain length.

For desorption, the rate decreased with increasing carbon chain length. The total percentage of LAS desorbed decreased with increasing carbon chain length.

For the equilibrium isotherms, various models were tested against the experimental data, including quadratic, BET, and cubic, and combined models using the previous in combination with Langmuir, and Freundlich models. A sum of the Langmuir and quadratic terms matched with the experimentally seen LAS data. At low concentrations, the LAS behaviour follows the Langmuir model, while at higher concentrations, it follows the quadratic model due to the formation of monolayers and bilayers.

Validity criteria fulfilled:

not applicable

Conclusions:

The macro-pore adsorption rate increased with increased carbon chain length (process 1), while the micro-pore adsorption rate increased with decreasing carbon chain length (process 2). The total percentage of LAS adsorbed increased with increasing carbon chain length.

For desorption, the rate decreased with increasing carbon chain length. The total percentage of LAS desorbed decreased with increasing carbon chain length.

For the equilibrium isotherms, various models were tested against the experimental data, including quadratic, BET, and cubic, and combined models using the previous in combination with Langmuir, and Freundlich models. A sum of the Langmuir and quadratic terms matched with the experimentally seen LAS data. At low concentrations, the LAS behaviour follows the Langmuir model, while at higher concentrations, it follows the quadratic model due to the formation of monolayers and bilayers.

Executive summary:

The kinetics of LAS adsorption and desorption to soil were studied. Concentrations of 5 -1800 mg/L LAS were studied, and exposures times of up to 61 hrs were studied. The adsorption/desorption rates were found to depend on the carbon chain length of the homologue, and the adsorption/desorption behaviour was found to follow a combined Langmuir/quadratic model.

Reference 4

Endpoint:

adsorption / desorption, other

Remarks:

adsorption/desorption

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
Refer to Section 13.2 for read-across justification document.

Reason / purpose for cross-reference:

read-across source

The macro-pore adsorption rate increased with increased carbon chain length (process 1), while the micro-pore adsorption rate increased with decreasing carbon chain length (process 2). The total percentage of LAS adsorbed increased with increasing carbon chain length.

For desorption, the rate decreased with increasing carbon chain length. The total percentage of LAS desorbed decreased with increasing carbon chain length.

For the equilibrium isotherms, various models were tested against the experimental data, including quadratic, BET, and cubic, and combined models using the previous in combination with Langmuir, and Freundlich models. A sum of the Langmuir and quadratic terms matched with the experimentally seen LAS data. At low concentrations, the LAS behaviour follows the Langmuir model, while at higher concentrations, it follows the quadratic model due to the formation of monolayers and bilayers.

Validity criteria fulfilled:

not applicable

Conclusions:

The macro-pore adsorption rate increased with increased carbon chain length (process 1), while the micro-pore adsorption rate increased with decreasing carbon chain length (process 2). The total percentage of LAS adsorbed increased with increasing carbon chain length.

For desorption, the rate decreased with increasing carbon chain length. The total percentage of LAS desorbed decreased with increasing carbon chain length.

For the equilibrium isotherms, various models were tested against the experimental data, including quadratic, BET, and cubic, and combined models using the previous in combination with Langmuir, and Freundlich models. A sum of the Langmuir and quadratic terms matched with the experimentally seen LAS data. At low concentrations, the LAS behaviour follows the Langmuir model, while at higher concentrations, it follows the quadratic model due to the formation of monolayers and bilayers.

Executive summary:

In a one-to-one read-across approach, the substance benzenesulfonic acid, 4-C10-13-sec-alkyl derivs. (source substance) is considered appropriate for direct read-across (one-to-one) to benzenesulfonic acid, 4-C10-13-sec-alkyl derivs., ammonium salts (target substance) for the endpoint adsorption/desorption.

The kinetics of LAS adsorption and desorption to soil were studied. Concentrations of 5 -1800 mg/L LAS were studied, and exposures times of up to 61 hrs were studied. The adsorption/desorption rates were found to depend on the carbon chain length of the homologue, and the adsorption/desorption behaviour was found to follow a combined Langmuir/quadratic model.

Description of key information

In the key study (Temmink and Klapwijk 2004), 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 C12LAS (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 C12LAS, 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.

In a supporting study, the kinetics of the absorption-desorption of LAS (read across) as well as equilibrium isotherms were determined in batch studies for commercial LAS as well as LAS homologues C10, C11, C12and C13. A multiple pseudo-first order kinetic model provided the best fit to the kinetic data, indicating the presence of two adsorption-desorption processes. Equilibrium adsorption and desorption data demonstrate acceptable fit (R2>0.99) to a model consisting of a Langmuir plus a quadratic term, which provided an integrated description of the experimental data over a wide range of LAS concentrations (5-1800 mg/L tested). At low concentrations, the Langmuir term explained the adsorption of LAS on soil sites which were highly selective of the n-alkyl groups and covered a very small fraction of the soil surface area, whereas the quadratic term described adsorption on the much larger part of the soil surface and on LAS retained at moderate to high concentrations.

Key value for chemical safety assessment

Koc at 20 °C:

2 500

Other adsorption coefficients

Type:

log Kp (solids-water in effluent sewage sludge)

Value in L/kg:

2 500

at the temperature of:

20 °C

Additional information

Investigations of adsorption-desorption of LAS (read across) indicate that when commercial LAS is mixed with activated sludge, almost all of the LAS (92 -98%, Kp=2,500 L/kg, log Kp= 3.4) would sorb to the sludge in under 10 minutes, and that while most of the added LAS sorbed to the sludge, it was available for biodegradation, which removed more than 99%.