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Environmental fate & pathways

Hydrolysis

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Administrative data

Endpoint:
hydrolysis
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study meets generally accepted scientific principles

Data source

Reference
Reference Type:
publication
Title:
Ion exchange and hydrolysis of Type A zeolite in natural waters
Author:
Allen HE, Cho SH and Neubecker TA
Year:
1983
Bibliographic source:
Water Res., 17 , 1871-1879

Materials and methods

Principles of method if other than guideline:
A suspension of a surface modified zeolite in different waters was studied for hydrolysis as indicated by loss of both particulate aluminum and particulate silicon.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Type A Zeolite
- Chemical name: Zeolite, cuboidal, crystalline, synthetic, non-fibrous
- Framework: cuboidal
- Related CAS number: 1318-02-1
- Analytical purity: no data
- surface modified with Ca

Study design

Analytical monitoring:
yes
Duration of test
Duration:
30 d
Initial conc. measured:
ca. 7 other: µmol/L (particulate aluminium and silicon concentration)

Results and discussion

Transformation products:
no
Dissipation DT50 of parent compound
pH:
8.2
DT50:
ca. 2 mo

Any other information on results incl. tables

Type A Zeolite hydrolysed extensively in the test waters at rates which were strongly dependent on hydrogen ion concentration (see Table 2).

Table 2: Increasing hydrolysis of Zeolite A within 3 days in synthetic test water with decreasing pH
-----------------------------------------------------------
 pH                         % zeolite
                               hydrolysed
-----------------------------------------------------------
 8.2                         44%
 7.1                         59%
 6.3                         72%
-----------------------------------------------------------

Hydrolysis results for the synthetic water and different natural waters are given as estimated hydrolytic half-lifes (see Table 3).

Table 3: Estimated hydrolytic half-lifes of Zeolite A in different natural waters
-----------------------------------------------------------
 water type                                      t1/2 [d]
-----------------------------------------------------------
 Lake Michigan                                   27
 Lake Michigan                                   31
   + 15% sewage effluent
 Ohio River                                       n.d.
 Miami River                                  ca. 150
 Raccoon Creek                    1
 Raccoon River                    slow
 Town River                                       2
 Synthetic water                  60
   (EPA Guidelines)
-----------------------------------------------------------

The results indicate that hydrolysis of Zeolite A does occur in the environment. The rate of this reaction depends on the pH and the silicate concentration in the water. The half-life of 60 d observed in the synthetic water with a high pH and high silicate concentration is very likely an overestimation of the hydrolysis half-life. Therefore, it yields a conservative prediction of Zeolite A persistance under most circumstances.

Applicant's summary and conclusion