Diiron trioxide

Additional information on environmental fate and behaviour

Administrative data

Endpoint:

additional information on environmental fate and behaviour

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other:

Remarks:

Test procedure in accordance with generally accepted scientific standards and described in sufficient detail. However, medium used did not contain many ions and stability measurements only conducted for 80 min.

Data source

Reference

Reference Type:

publication

Title:

The effects of extracellular polymeric substances on magnetic iron oxide nanoparticles stability and the removal of microcystin-LR in aqueous environments

Author:

Yang, Y., Hou J., Wang P., Wang C., Miao L., Ao Y., Wang X., Lv B., You G., Liu Z., Shao Y.

Year:

2018

Bibliographic source:

Ecotoxicology and Environmental Safety, volume 148, pages 89 - 96

Materials and methods

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

Interaction between extracellular polymeric substances (EPS) from cyanobacteria and alginic acid sodium salt (AASS) from brown algae with iron oxide nanoparticles (gamma-Fe2O3) was studied in an aqueous solution, and in combination with the cyanotoxin microcystin-LR.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Diiron trioxide

EC Number:

215-168-2

EC Name:

Diiron trioxide

Cas Number:

1309-37-1

Molecular formula:

Fe2O3

IUPAC Name:

diiron(3+) trioxidandiide

Test material form:

solid: nanoform

Details on test material:

Purity: no information
Crystalline phase: maghemite
Particle size: 50 - 80 nm (SEM)
Mean hydrodynamic diameter: 244 ± 17 nm (Milli-Q water)
Surface charge (zeta potential in Milli-Q water): 29.2 ± 0.3 mV
obtained from Sigma-Aldrich (544884)

Results and discussion

Any other information on results incl. tables

Characteristics of IONPs and NOM:

- The HDD of the IONPs measured by DLS was much larger than the primary particle size.

- The zeta-potential of different NOM used in this study was negative under the experimental conditions.

Table 1: Properties of IONPs and NOM used in this study, determined in Milli-Q water at pH 7 (± standard deviation), n = 3.

Contents	Hydrodynamic diameter (nm)	Zeta potential (mV)	Point of zero charge in ultrapure water	Concentration (mg/L)
IONPs	244 ± 17	29.2 ± 0.3	7.9	100
EPS-M1	124.7 ± 27	- 22.1 ± 6.5	5.2	200
EPS-M9	196.2 ± 19	- 21.3 ± 0.6	5.4	200
AASS	35.6 ± 1.4	- 60.9 ± 4.9	4.1	200

Stability of IONPs:

- The different types of NOM and different concentrations affected the stability of IONPs. The presence of 1 mg/L of EPS-M1 or EPS-M9 inhibited the sedimentation of IONPs to a greater extent (39% and 26% remaining suspended fraction for M1 and M9 respectively) than the presence of 1 mg/L of AASS (6% remaining suspended fraction) after 80 min.

- Higher concentrations of AASS stabilized the IONP suspension more, at 10 mg/L AASS 40% of IONPs remained as suspended fraction and approximately 25% remained suspended at 50 mg/L AASS.

- In contrast, suspended fractions of IONPs decreased by adding 10 mg/L of M1 (14%) or M9 (18%), and no obvious stabilizing effect was observed compared to the control when adding 50 mg/L of M1 or M9.

- In the control, where no NOM was added, approximately 10% of IONPs (graphically derived) remained suspended after 80 min, suggesting low suspension stability of IONPs without addition of NOM.

- The zeta-potential of IONPs measured at different EPS-M1/M9 concentrations steadily decreased from 29.2 mV at 1 mg/L EPS to 1.62 mV at 50 mg/L EPS.

- DLS measurements revealed, that IONPs aggregated significantly with the addition of 5 mM NaCl (pH 7), as HDD increased from ~ 250 nm to ~ 1750 nm within 40 min.

- In the presence of NOM, the HDD of IONPs increased less obviously, as the HDD increased only to ~ 400 nm (10 mg/L M1) and ~ 350 nm (10 mg/L M9), respectively, after 40 min.

- In this study, EPS-M1 and EPS-M9 exhibited a stronger ability to stabilized IONPs than AASS under experimental conditions.

Applicant's summary and conclusion

Conclusions:

This study investigates the influence of extracellular polymeric substances from cyanobacteria (Microcystis aeruginosa) and brown algae on the properties and stability of maghemite nanoparticles (gamma-Fe2O3) in aqueous solutions. The experiments showed that a better dispersion of IONPs was observed in the presence of EPS and AASS (NOM from cyanobacteria and brown algae) due to electrostatic repulsion. Suspension stability measurements by UV-vis revealed that without addition of NOM, approximately only 10% of IONPs remained suspended after 80 min. In contrast, especially low concentrations of EPS (1 mg/L) and higher concentrations of AASS (10 mg/L) enhanced the stability of IONPs, since up to 40% of IONPs remain suspended after 80 min. However, as the NOM concentrations in the actual environment could be higher and the water chemistry is more complex than that used in this study, the applicability of the results is subject to uncertainty. Furthermore, the stability of the suspension was determined after a relatively short period of time.