Barium sulfate

Nanomaterial photocatalytic activity

Administrative data

Endpoint:

nanomaterial photocatalytic activity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Nanospecific guidance in REACH: a comparative physical-chemical characterization of 15 materials with methodical correlations

Author:

Wohlleben W. et al.

Year:

2013

Bibliographic source:

Journal of Ceramic Science and Technology, volume 4, pages 93 - 104

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

2014

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

other: DIN 52980:2800-10, Photocatalytic activity of surfaces - Determination of photocatalytic activity of surfaces in an aqueous medium by degradation of methylene blue

Principles of method if other than guideline:

The photocatalytic activity of nano-BaSO4 (NM-220) was determined using a methylene blue degradation test closely following DIN 52980:2800-10. NM-220 was dispersed in an aqueous solution containing methylene blue at 5 mg/L. Beakers (20 mL) with the test dispersion were placed in an irradiation chamber (MRC Systems GmbH) and a constant UV intensity of 1 mW/cm2 at 350 nm was maintained.

Under constant stirring, the remaining dye absorption at 0 h, 2 h, 6 h and 22 h was measured in aliquots using cuvettes (1 cm) outside of the irradiation chamber. As negative control, suspensions of identical composition were kept in the dark and were measured at the same time points. According to the DIN standard, the unit-less photon efficiency was calculated.

No measurable degradation under UV irradiation was determined in a dye solution without nanoparticles as additional negative control.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Barium sulfate

EC Number:

231-784-4

EC Name:

Barium sulfate

Cas Number:

7727-43-7

Molecular formula:

BaO4S

IUPAC Name:

barium sulfate

Test material form:

solid: nanoform

Details on test material:

BaSO4 (NM-220 batch):
- Crystallite size (XRD): 36.0 nm
- Crystalline phase (XRD): Barite orthorhombic
- Particle size distribution (TEM): primary particle diameter: 25 ± 10 nm
- State of Agglomeration (SEM): agglomerate diameter: 2,800 nm to 15,000 nm, sphere
- Specific surface area: surface area: 38 m2/g
- Hg-intrusion porosimetry (DIN 66133): pore sizes: 30 nm, 5000 nm
- Surface chemistry (XPS): ζ-pot at pH 7: -2.2(μm/s)/V/cm)
- Surface charge: IEP at pH 3.3 ± 0.2
- Electrophoretic mobility with pH titration: ZP: -28 ± 2 mV
- Photocatalytic activity (DIN methylene blue assay): 1.1 + 0.2 -1.1 x 10E-3
(compatible with zero)
- Dispersability (AUC, ISO13318: D50/AAN*): 116 nm/4.6 (in water), 285 nm/11 (in DMEM/FCS)
- Solubility (ICP-MS):
in water 1 d: 0.05 wt%
in DMEM/FCS 1d: 0.02 wt%
in PSF 28 d: 0.1 wt% (recrystallizes)
in PBS 28 d: 0.1 wt%
in FaSSIF 7 d: 0.1 wt%
in 0.1N HCl 1 d: 1.0 wt%
- Impurities: Water and 1.8% organic additives (mass loss in TGA)
- Neutron activation analysis: 599,000 ± 33,000 µg Ba/g (59.9 wt%)

*Remarks: the BaSO4 NPs (NM-220) used for these studies were a reference material prepared for the Nanomaterial Testing Sponsorship Program of the Organization for Economic Cooperation and Development (OECD). The characterization of the original batch distributed as NM-220 has been published (Wohlleben et al. (2013)).** Since Study 1 (2-year inhalation) requires large amounts, BaSO4 NPs were reproduced at a different production plant using the same synthesis protocol.

**Reference:
- Wohlleben, W. et al. (2013): Nanospecific guidance in REACH: A comparative physical-chemical characterization of 15 materials with methodical correlations. J. Ceram. Sci. Tech 4: 93–104.

Results and discussion

Photocatalytic activity

Mean:

0.001 other: photon efficiency

Remarks on result:

other: based on methylene blue assay

Any other information on results incl. tables

The photon efficiency of NM-220 comparable to zero as no degradation of the dye was observed under UV irradiation after 2, 6 and 22 hours of incubation.

Applicant's summary and conclusion

Conclusions:

The photocatalytic activity of nano-BaSO4 (NM-220) is extremely low and comparable to zero, as shown by the absence of methylene blue degradation.