Zeolite, silica and sodium and titanium based, crystalline, synthetic, non fibrous

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

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

Adequacy of study:

other information

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

Test material information

Constituent 1

Reference substance name:

Automatically generated during migration to IUCLID 6, no data available

IUPAC Name:

Automatically generated during migration to IUCLID 6, no data available

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.