Aluminium nitride

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Data waiving:

study technically not feasible

Justification for data waiving:

other:

Reason / purpose for cross-reference:

data waiving: supporting information

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

No data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

GLP compliance:

not specified

Remarks:

No data available, publication.

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

no

Test temperature:

25 °C

Analytical monitoring:

yes

Details on sampling:

No details reported

Matrix no.:

#1

Matrix type:

other: Clay, kaolonite

CEC:

8.03 other: mmol/100 g

Matrix no.:

#2

Matrix type:

other: Clay, vermiculite

CEC:

119.07 other: mmol/100 g

Matrix no.:

#3

Matrix type:

other: Clay, calcium montmorillonite

CEC:

106.83 other: mmol/100 g

Matrix no.:

#4

Matrix type:

other: Clay, palygorskite

CEC:

21.23 other: mmol/100 g

Matrix no.:

#5

Matrix type:

other: Clay, sepiolite

CEC:

18.9 other: mmol/100 g

Matrix no.:

#6

Matrix type:

other: Clayl, halloysite

CEC:

6.1 other: mmol/100 g

Details on matrix:

COLLECTION AND STORAGE
- Geographic location: All natural clay minerals were collected from China, namely:
* kaolinite (Kaol) sample from Maoming, Guangdong province,
* vermiculite (Ver) sample from Lingshou, Hebei province,
* calcium montmorillonite (Mt) sample from Chifeng, Inner Mongolia,
* palygorskite (Pla) sample from Mingguang, Anhui Province,
* sepiolite (Sep) sample from Baoding, Hebei province, and
* halloysite (Hal) sample from Linfen, Shanxi province
- Collection procedures: not reported
- Sampling depth (cm): not reported
- Storage conditions: not reported
- Storage length: not reported
- Soil preparation: clay samples were pulverized and passed through a 74 μm sieve, and subsequently washed with distilled water to remove soluble matter and oven-dried at 100 °C for 24 h

Details on test conditions:

1. Batch adsorption experiments
- 1000 mg/L NH4Cl stock solution was further diluted with distilled water to get the desired experimental working solutions.
- Experiments were carried out using stopper test tube (50 mL) in a thermostatic shaker with clay mineral/liquid ratio of 0.3 g/25 mL.
- Dtermination of NH4+ concentration in solution by means of the Nessler's method with anm UV–vis spectrophotometer at 420 nm (UV-759S, Jinghua, China).
- Quality control testing included experiments with blanks and duplicates.

1.1 Adsorption kinetics experiments
- The optimum time required for the NH4+ adsorption to attain equilibrium was determined as a function of contact time in the range of 5–120 min
- NH4+ concentration: 10 mg/L
- pH: 7
- T: 25 °C

1.2 Adsorption isotherm experiments
- To investigate the effect of initial NH4+ concentration on the removal capacity of NH4+ in the batch adsorption experiment
- Concentration range: 10–1500 mg/L
- Duration: 2 h

1.3 Effect of solution pH on NH4+ adsorption
- pH range: of 2–10 pH
- NH4+ concentration: 30 mg NH4+/L
- Duration: 2 h.
- The initial pH was adjusted by 1 M HCl or NaOH solution.

1.4.Effect of clay dosage on NH4+ adsorption
- Clay amount: 0.1–0.5 g
- Initial NH4+ concentration: 30 mg/L
- Duration: 2 h
- Calculation of the removal efficiency (%) for the six clays and the equilibrium adsorption capacity (qe) were calculated, respectively by using the following equations:
Removal efficiency (%) = ((Co - Ce)/ Co) x 100
qe = (C0-Ce) V/ M
where Co = initial ammonium concentration (mg/L), Ce = equilibrium ammonium concentration (mg/L), qe = adsorption capacity (mg/g), V = volume of the ammonium solution (L), and M = mass of natural clay mineral (g).

Sample No.:

#1

Duration:

30 min

Initial conc. measured:

>= 10 - <= 1 500 other: mg NH4+/L

pH:

7

Temp.:

25 °C

Sample No.:

#2

Duration:

30 min

Initial conc. measured:

>= 10 - <= 1 500 other: mg NH4+/L

pH:

7

Temp.:

25 °C

Sample No.:

#3

Duration:

30 min

Initial conc. measured:

>= 10 - <= 1 500 other: mg NH4+/L

pH:

7

Temp.:

25 °C

Sample No.:

#4

Duration:

30 min

Initial conc. measured:

>= 10 - <= 1 500 other: mg NH4+/L

pH:

7

Temp.:

25 °C

Sample No.:

#5

Duration:

30 min

Initial conc. measured:

>= 10 - <= 1 500 other: mg NH4+/L

pH:

7

Temp.:

25 °C

Sample No.:

#6

Duration:

30 min

Initial conc. measured:

>= 10 - <= 1 500 other: mg NH4+/L

pH:

7

Temp.:

25 °C

Sample No.:

#1

Type:

Kd

Remarks:

Langmuir constant

Value:

0.092 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Kaolinite

% Org. carbon:

>= 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Sample No.:

#2

Type:

Kd

Remarks:

Langmuir constant

Value:

0.301 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Vermiculite

% Org. carbon:

>= 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Sample No.:

#3

Type:

Kd

Remarks:

Langmuir constant

Value:

0.227 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Calcium montmorillinite

% Org. carbon:

>= 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Sample No.:

#4

Type:

Kd

Remarks:

Langmuir constant

Value:

0.223 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Palygorskite

% Org. carbon:

> 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Sample No.:

#5

Type:

Kd

Remarks:

Langmuir constant

Value:

0.156 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Sepiolite

% Org. carbon:

>= 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Sample No.:

#6

Type:

Kd

Remarks:

Langmuir constant

Value:

0.092 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Halloysite

% Org. carbon:

>= 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Transformation products:

no

Adsorption characteristics of NH4+ onto natural clay minerals

1. Adsorption kinetics

- Removal efficiency of NH4+: increases with the increasing reaction time and reaches equilibrium in 30 min.

- To further investigate the adsorption behavior, pseudo-first order and pseudo-second-order kinetics models were used to analyze the obtained data and can be summarized as follows.

- The linear equations of pseudo-first, pseudo-second order models for boundary conditions of qe = 0 at t = 0 and qt = qe at t = te are as follows:

* The pseudo-first order: ln(qe − qt) = lnqe − k1t

* Pseudo-second order: t/qt = 1/(k2qe²) + (1/qe)t ; h = k2qe²

where qt = adsorption capacity at time t (mg/g),

k1and k2: adsorption constants (1/min) and (g/mg min), respectively, and

h = rate of adsorption (mg/g min).

- Results indicate that the adsorption kinetics of NH4+ is of pseudo-second-order

2. Effect of solution pH

- The removal efficiency of NH4+ increases with increasing pH from 2.0 to 7.0. With further increasing pH (up to pH 10) , it decreases steadily:

* pH < 7: negative charge on the clay mineral surface declines due to the excess protons in solution and competition for adsorption/exchange sites onto clay particles

* pH > 7: the removal efficiency of NH4+ decreases as NH4+ is transformed to aqueous NH3

--> Further experiments were performed at pH 7.

3. Effect of clay dosage

- The removal efficiency of NH4+ ions by increases with increasing adsorbent dosage from 0.1 g to 0.5 g.

- Basis fro effect: increasing number of active surface sites for NH4+ adsorption

--> 0.3 g was selected as the optimal dosage for all clays and used in the subsequent experiments.

4. Asorption isotherms

- Increase in the adsorption capacities for all clays with an increase of initial ammonium concentration from 10 to 1,000 mg NH4+/ L. At even higher concentrations, no remarkable change in adsorption capacities were noted.

- Vermiculite has the highest adsorption capacity followed by calcium montmorilinite. The adsorption capacity as such is presumably related to the high amount of exchangeable cations (such as Ca2+ and Na+) present in both clay types.

- The two main isotherm models, Langmuir model (LM) and Freundlich model (FM) were used to describe the experimental results of NH4+ as follow:

* LM adsorption isotherm: Ce/qe = 1/Kqmax + (1/qmax)Ce

where

K = Langmuir constant (L/mg)

qmax = max. adsorption capacity (mg/g).

* Freundlich model: log qe = log kF + 1/n log Ce

where

kF = Freundlich adsorbent capacity (mg/g (L/mg)1/n)

n = reciprocal of reaction order

- Results idicate the Langmuir model has a better fit for NH4+ adsorption on clay (R² > 0.92) than Freundlich model, indicating that the adsorption process of NH4+ by clay is a monolayer adsorption.

Validity criteria fulfilled:

not applicable

Conclusions:

NH4+ from aqueous solution strongly adsorbs to clay. The main driver of the adsorption is the cation exchange capacity (CEC) of the clay.

Executive summary:

Six different clay types (kaolinite, halloysite, montmorillonite, vermiculite, palygorskite, and sepiolite) were used in this study to investigate the adsorption of ammonium (NH₄⁺) from aqueous solution. Experiments were conducted at 0.3 g clay/25 mL NH₄⁺solution at pH 7.

NH₄⁺ solutions were applied to clay samples at concentrations ranging between 10 and 1,500 mg/L.

Adsorption equilibrium was quickly achieved after 30 minutes of exposure. Adsorption was measured by quantifying the remaining NH₄⁺ in aqueous solution by means of UV-vis spectrometry after the equilibrium was reached.

Adsorption kinetics showed that the adsorption behaviour followed the pseudo-second-order kinetic model. The adsorption isotherms fitted by the Langmuir model illustrated that among all the clay types studied, vermiculite (50.06 mg/g) and montmorillonite (40.84 mg/g) showed the highest ammonium adsorption capacities. The main parameter driving NH₄⁺ adsorption in soil is the cation exchange capacity (CEC).

Reference 3

Endpoint:

adsorption / desorption: screening

Type of information:

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

Adequacy of study:

key study

Study period:

No data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Justification for type of information:

Aluminium nitride (AlN) as such is not soluble in water. However, aluminium nitride undergoes hydrolytic transformation in contact with water, predominantly forming insoluble aluminium salts like bayerite, Al(OH)3, and polymeric aluminium hydroxide species. In addition to aluminium, ammonia is formed as an important product of hydrolysis upon contact of aluminium nitride with water (e.g. soil pore water). Thus, read-across to the transformation products is applied to fulfil the endpoint requirements for adsorption/desorption screening.
For further details and justification of read-across please refer to the report attached in section 13 of IUCLID which provides information on the hypothesis for the analogue approach, information on purity and impurities of source and target chemical(s), the analogue approach justification as well as the data matrix.

Reason / purpose for cross-reference:

read-across source

Radiolabelling:

no

Sample No.:

#1

Type:

Kd

Remarks:

Langmuir constant

Value:

0.092 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Kaolinite

% Org. carbon:

>= 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Sample No.:

#2

Type:

Kd

Remarks:

Langmuir constant

Value:

0.301 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Vermiculite

% Org. carbon:

>= 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Sample No.:

#3

Type:

Kd

Remarks:

Langmuir constant

Value:

0.227 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Calcium montmorillinite

% Org. carbon:

>= 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Sample No.:

#4

Type:

Kd

Remarks:

Langmuir constant

Value:

0.223 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Palygorskite

% Org. carbon:

> 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Sample No.:

#5

Type:

Kd

Remarks:

Langmuir constant

Value:

0.156 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Sepiolite

% Org. carbon:

>= 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Sample No.:

#6

Type:

Kd

Remarks:

Langmuir constant

Value:

0.092 other: L/mg

pH:

7

Temp.:

25 °C

Matrix:

Halloysite

% Org. carbon:

>= 1 - <= 2

Remarks on result:

other: Organic carbon (OC) was not reported in the present study. According to information from OECD guideline 106, the OC content in clay is typically between 1 and 2 %.

Transformation products:

no

Adsorption characteristics of NH4+ onto natural clay minerals

1. Adsorption kinetics

- Removal efficiency of NH4+: increases with the increasing reaction time and reaches equilibrium in 30 min.

- To further investigate the adsorption behavior, pseudo-first order and pseudo-second-order kinetics models were used to analyze the obtained data and can be summarized as follows.

- The linear equations of pseudo-first, pseudo-second order models for boundary conditions of qe = 0 at t = 0 and qt = qe at t = te are as follows:

* The pseudo-first order: ln(qe − qt) = lnqe − k1t

* Pseudo-second order: t/qt = 1/(k2qe²) + (1/qe)t ; h = k2qe²

where qt = adsorption capacity at time t (mg/g),

k1and k2: adsorption constants (1/min) and (g/mg min), respectively, and

h = rate of adsorption (mg/g min).

- Results indicate that the adsorption kinetics of NH4+ is of pseudo-second-order

2. Effect of solution pH

- The removal efficiency of NH4+ increases with increasing pH from 2.0 to 7.0. With further increasing pH (up to pH 10) , it decreases steadily:

* pH < 7: negative charge on the clay mineral surface declines due to the excess protons in solution and competition for adsorption/exchange sites onto clay particles

* pH > 7: the removal efficiency of NH4+ decreases as NH4+ is transformed to aqueous NH3

--> Further experiments were performed at pH 7.

3. Effect of clay dosage

- The removal efficiency of NH4+ ions by increases with increasing adsorbent dosage from 0.1 g to 0.5 g.

- Basis fro effect: increasing number of active surface sites for NH4+ adsorption

--> 0.3 g was selected as the optimal dosage for all clays and used in the subsequent experiments.

4. Asorption isotherms

- Increase in the adsorption capacities for all clays with an increase of initial ammonium concentration from 10 to 1,000 mg NH4+/ L. At even higher concentrations, no remarkable change in adsorption capacities were noted.

- Vermiculite has the highest adsorption capacity followed by calcium montmorilinite. The adsorption capacity as such is presumably related to the high amount of exchangeable cations (such as Ca2+ and Na+) present in both clay types.

- The two main isotherm models, Langmuir model (LM) and Freundlich model (FM) were used to describe the experimental results of NH4+ as follow:

* LM adsorption isotherm: Ce/qe = 1/Kqmax + (1/qmax)Ce

where

K = Langmuir constant (L/mg)

qmax = max. adsorption capacity (mg/g).

* Freundlich model: log qe = log kF + 1/n log Ce

where

kF = Freundlich adsorbent capacity (mg/g (L/mg)1/n)

n = reciprocal of reaction order

- Results idicate the Langmuir model has a better fit for NH4+ adsorption on clay (R² > 0.92) than Freundlich model, indicating that the adsorption process of NH4+ by clay is a monolayer adsorption.

Validity criteria fulfilled:

not applicable

Conclusions:

NH4+ from aqueous solution strongly adsorbs to clay. The main driver of the adsorption is the cation exchange capacity (CEC) of the clay.

Executive summary:

Six different clay types (kaolinite, halloysite, montmorillonite, vermiculite, palygorskite, and sepiolite) were used in this study to investigate the adsorption of ammonium (NH₄⁺) from aqueous solution. Experiments were conducted at 0.3 g clay/25 mL NH₄⁺ solution at pH 7.

NH₄⁺ solutions were applied to clay samples at concentrations ranging between 10 and 1,500 mg/L.

Adsorption equilibrium was quickly achieved after 30 minutes of exposure. Adsorption was measured by quantifying the remaining NH₄⁺ in aqueous solution by means of UV-vis spectrometry after the equilibrium was reached.

Adsorption kinetics showed that the adsorption behaviour followed the pseudo-second-order kinetic model. The adsorption isotherms fitted by the Langmuir model illustrated that among all the clay types studied, vermiculite (50.06 mg/g) and montmorillonite (40.84 mg/g) showed the highest ammonium adsorption capacities. The main parameter driving NH₄⁺ adsorption in soil is the cation exchange capacity (CEC).

 This information is used in a read-across approach in the assessment of the target substance. For justification of read-across please refer to the attached read-across report (see IUCLID section 13).

Description of key information

Adsorption/desorption is not relevant for aluminium nitride.

Additional information

In accordance with REACH Annex XI, section 2, “testing for a specific endpoint may be omitted, if it is technically not possible to conduct the study as a consequence of the properties of the substance”.

Aluminium nitride (AlN) as such is not soluble in water. Since adsorption/desorption testing requires the test substance to be dissolved in aqueous medium, testing of the adsorption/desorption behaviour of AlN as such is technically not feasible. However, aluminium nitride undergoes hydrolytic transformation in contact with water, predominantly forming insoluble aluminium salts like bayerite, Al(OH)₃, and polymeric aluminium hydroxide species. Free Al³⁺ ions are also released in low amounts, at maximum ca. 1 mg/L, positively related to the loading rate (see section 5.1.2 of this IUCLID dossier). Therefore, aluminium nitride as such cannot be tested for adsorptive properties.

The adsorption/desorption from the soluble fraction of Al³⁺ generated in contact with water is influenced and at the same time also superimposed by other effects occuring in soil, rendering it impossible to measure only the adsorption behaviour of soluble Al³⁺ deliberately added to soil matrix in an experimental setup. In view of the high abundance of aluminium in soil, aluminium deliberately added to the soluble fraction in laboratory experiments is indistinguishable from soil-originated aluminium, preventing quantification of the test material; accordingly, differentiation of adsorption and desorption processes is technically not feasible.

In addition to aluminium, ammonia is formed as an important product of hydrolysis upon contact of aluminium nitride with water (e.g. soil pore water). Ammonium has a strong tendency to adsorb to soil. Adsoption is driven by the cation exchange capacity (CEC) of the soil.