Sodium polysulfide aluminosilicate with a SOD-type framework structure

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Data waiving:

study technically not feasible

Justification for data waiving:

the study does not need to be conducted because the substance is highly insoluble in water

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
In accordance with column 2 of REACH Annex VIII, the hydrolysis as a function of pH study ( required in section 9.2.2.1) does not need to be conducted as the substance is a highly insoluble substance.

Reference 2

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Remarks:

No data on GLP. The study provides scientifically valid information on the hydrolysis of the substance.

Principles of method if other than guideline:

The ion exchange behaviour and hydrolysis rate of the detergent builder Type A zeolite have been studied in a variety of artificial and natural surface water samples. The experiments were conducted at zeolite A and trace metal concentrations characteristic of what could occur in receiving waters.

GLP compliance:

not specified

Analytical monitoring:

yes

Details on test conditions:

Fresh-stock zeolite suspensions containing 1.23 g/l of calcium-form zeolite (1.0 g/l on an anhydrous basis) in the appropriate synthetic or natural water were used for the preparation of samples. The stock suspension was kept completely dispersed by continual stirring and by ultrasonic mixing for the initial 30 s. Based on analysis of particulate calcium, aluminum and silicon there was no evidence of hydrolysis (< 1%) over the time period required for the preparation of a series of experimental samples. Samples were prepared by the addition of zeolite suspension and test water to make 1 l in acid-washed, polyethylene bottles. The samples were continuously shaken at 40 cycles/min for the desired time of up to 30 weeks. The pH of the samples was that established by their equilibration with the atmosphere; approx, pH 8.2 in the case of the synthetic waters. For the synthetic water samples used to study the effect of pH on hydrolysis and ion exchange and for equilibrating zeolite with trace metals for the study of metal release, mixing and pH control were achieved by bubbling an appropriate nitrogen-carbon dioxide mixture (Roberts and Allen, 1972) through the sample.

Transformation products:

not specified

Details on results:

The data indicate that Type A zeolite hydrolyzed extensively in the test waters at rates which were strongly dependent on hydrogen ion concentration. Half-lives of 1-2 months were typical for waters at a neutral pH.

Effect of pH: The results of this experiment showed that the rate of zeolite hydrolysis increased with decreasing pH.

Conclusions:

Type A zeolite hydrolyzes extensively in natural waters with a typical half-life of 1-2 months. This rate will be accelerated at low pH and retarded by high concentrations of hydrolysis products.

Executive summary:

The ion exchange behaviour and hydrolysis rate of the detergent builder Type A zeolite have been studied in a variety of artificial and natural surface water samples. The experiments were conducted at zeolite A and trace metal concentrations characteristic of what could occur in receiving waters. Type A zeolite hydrolyzes extensively in natural waters with a typical half-life of 1-2 months. This rate will be accelerated at low pH and retarded by high concentrations of hydrolysis products.

Reference 3

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Remarks:

No data on GLP. The study provides scientifically valid information on the hydrolysis of the substance.

Principles of method if other than guideline:

The aqueous solution degradation of zeolite A was studied by measuring the uptake of acid and the solubilization of silicon and aluminum with time at various pH values in the range 3-9. Sodium and calcium forms of zeolite A were studied under various fixed-volume and flow-through conditions; in distilled water, model environmental systems, and, actual sewage media. Zeolite A degradation products were characterized by scanning electron microscopy, infrared spectra, density measurements, oxygen adsorption, ion microprobe analysis, selected-area electron diffraction, X-ray diffraction, and X-ray fluorescence.

GLP compliance:

not specified

Analytical monitoring:

yes

As hydrolysis occurs, the unique zeolite A structure is destroyed, and the characteristics of the transformed solid approach those of common, naturally occurring minerals.

Conclusions:

As hydrolysis occurs, the unique zeolite A structure is destroyed, and the characteristics of the transformed solid approach those of common, naturally occurring minerals.

Executive summary:

The aqueous solution degradation of zeolite A was studied by measuring the uptake of acid and the solubilization of silicon and aluminum with time at various pH values in the range 3-9. Sodium and calcium forms of zeolite A were studied under various fixed-volume and flow-through conditions; in distilled water, model environmental systems, and, actual sewage media. Zeolite A degradation products were characterized by scanning electron microscopy, infrared spectra, density measurements, oxygen adsorption, ion microprobe analysis, selected-area electron diffraction, X-ray diffraction, and X-ray fluorescence. As hydrolysis occurs, the unique zeolite A structure is destroyed, and the characteristics of the transformed solid approach those of common, naturally occurring minerals.

Description of key information

Data waiving: Hydrolysis does not need to be conducted as the substance is a highly insoluble substance.

Additional information

Supporting information: Two studies on the behaviour of type A zeolites in water are available:

In one study, the acid uptake and solubilisation of silicon and aluminum versus time were determined in aqueous solutions of zeolite A at various pH values in the range 3 - 9. Sodium and calcium forms of zeolite A were studied under various fixed-volume and flow-through conditions: in distilled water, model environmental systems, and, actual sewage media. The formed degradation products were characterized by scanning electron microscopy (SEM), infrared spectra, density measurements, oxygen adsorption, ion microprobe analysis, selected-area electron diffraction, X-ray diffraction, and X-ray fluorescence. It was observed that, as hydrolysis occurs, the unique zeolite A structure is destroyed, and the characteristics of the transformed solid approach those of common, naturally occurring minerals (Cook, 1982). In another study, the ion exchange behaviour and hydrolysis rate of a type A zeolite was studied in a variety of artificial and natural surface water samples, with trace metal concentrations representative of what could occur in receiving waters. The test item was observed to hydrolise extensively, at rates which were strongly dependent on hydrogen ion concentration. Half-lives of 1-2 months were typical for waters at a neutral pH (Allen, 1983).

Based on the available data, compounds with this type of structure would be expected to hydrolyse into more simple products, similar to naturally occuring minerals, with a half-life of a few months, strongly dependant on pH.