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EC number: 236-675-5 | CAS number: 13463-67-7
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
![](https://echa.europa.eu./o/diss-blank-theme/images/factsheets/A-REACH/factsheet/print_physical-and-chemical-properties.png)
Nanomaterial Zeta potential
Administrative data
- Endpoint:
- nanomaterial Zeta potential
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 2019-05-17 to 2019-08-01
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- study well documented, meets generally accepted scientific principles, acceptable for assessment
Cross-referenceopen allclose all
- Reason / purpose for cross-reference:
- reference to same study
Reference
- Endpoint:
- nanomaterial Zeta potential
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 2019-05-17 to 2019-08-01
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- study well documented, meets generally accepted scientific principles, acceptable for assessment
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Sample TiO2 dispersion at 0.01% w/w was prepared by adding 20 mg of sample TiO2 powder to a stirring solution of 200 ml 10-3 M KCl in deionised water. To ensure dispersion, the solution was then stirred under shear for 1 minute at 2500 rpm.
The pH was then adjusted to pH 11 by addition of 0.01 M NaOH in deionised water. The conductivity was recorded, and a sample was taken for zeta potential measurement. The pH was lowered by 1 pH value by addition of 0.01 M HCl in deionised water, and the conductivity and zeta potential were recorded. This process was repeated to obtain final conductivity and zeta potential measurements across the pH range from pH 11 to pH 1. - GLP compliance:
- no
- Type of method:
- other: Dynamic light scattering (DLS), and pH meter and conductivity meter
- Sampling:
- please refer to `Principle of method of other than guideline´
- Specific details on test material used for the study:
- Product name: Sample G2-5
Appearance: white odourless powder
Substance stability: Stable under normal conditions
Substance humidity: 8.4 - Instruments:
- - Magnetic stirrer plate
- Silverson L5 mixer
- Conductivity and pH were measured using a Mettler Toledo Five Easy pH Meter F20-Std-Kit.
- Zeta potential was measured using a Horiba SZ-100 particle sizer. - Calibration:
- Both the pH meter and the conductivity meter were calibrated with standard buffers or conductivity standards, respectively, prior to use.
- Zeta potential:
- -39.1 mV
- St. dev.:
- 3.5 mV
- pH:
- 11
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -42.5 mV
- St. dev.:
- 3 mV
- pH:
- 10
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -19.4 mV
- St. dev.:
- 4.4 mV
- pH:
- 9
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -19.4 mV
- St. dev.:
- 2.9 mV
- pH:
- 8
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -10.4 mV
- St. dev.:
- 3.2 mV
- pH:
- 7
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 21.6 mV
- St. dev.:
- 16.2 mV
- pH:
- 6
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 36.3 mV
- St. dev.:
- 7.1 mV
- pH:
- 5
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 44.7 mV
- St. dev.:
- 1.8 mV
- pH:
- 4
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 15.8 mV
- St. dev.:
- 0.1 mV
- pH:
- 3
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 11.6 mV
- St. dev.:
- 1.8 mV
- pH:
- 2
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -25.6 mV
- St. dev.:
- 11.2 mV
- pH:
- 1
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Key result
- Isoelectric Point:
- 7
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Remarks on result:
- other: no St.dev. was stated
- Conclusions:
- The test item G2-5 has an approximate isoelectric point of 7.0 in a dispersion (0.01% w/w) in 10-3 M KCl in deionised water.
The point at which the curve crosses a zeta potential value of 0 mV is known as the isoelectric point, where the particles effectively carry no net electrical charge.
Conductivity measurements obtained for each sample remained fairly consistent from pH 4 to pH 11, which is an important property for zeta potential measurement. Below pH 4, conductivity was found to increase markedly, likely due to the substantial amounts of HCl needed in order to reach the low pH values. As a result, the concentration of TiO2 also decreased substantially in this pH range. In addition, the composition of each of the samples is not known. It is often found that TiO2 is coated with e.g. Al2O3 or ZrO2 which, especially in the case of Al2O3 exhibit increased solubility at pH values > pH 10. It is therefore strongly noted that data points below pH 4 and above pH 10 are unreliable in comparison to the rest of the data set.
- Reason / purpose for cross-reference:
- reference to same study
Reference
- Endpoint:
- nanomaterial Zeta potential
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 2019-05-17 to 2019-08-01
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- study well documented, meets generally accepted scientific principles, acceptable for assessment
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Sample TiO2 dispersion at 0.01% w/w was prepared by adding 20 mg of sample TiO2 powder to a stirring solution of 200 ml 10-3 M KCl in deionised water. To ensure dispersion, the solution was then stirred under shear for 1 minute at 2500 rpm.
The pH was then adjusted to pH 11 by addition of 0.01 M NaOH in deionised water. The conductivity was recorded, and a sample was taken for zeta potential measurement. The pH was lowered by 1 pH value by addition of 0.01 M HCl in deionised water, and the conductivity and zeta potential were recorded. This process was repeated to obtain final conductivity and zeta potential measurements across the pH range from pH 11 to pH 1. - GLP compliance:
- no
- Type of method:
- other: Dynamic light scattering (DLS), and pH meter and conductivity meter
- Sampling:
- please refer to `Principle of method of other than guideline´
- Specific details on test material used for the study:
- Product name: Sample G6-3
Appearance: white odourless powder
Substance stability: Stable under normal conditions
Substance humidity: 0.4 - Instruments:
- - Magnetic stirrer plate
- Silverson L5 mixer
- Conductivity and pH were measured using a Mettler Toledo Five Easy pH Meter F20-Std-Kit.
- Zeta potential was measured using a Horiba SZ-100 particle sizer. - Calibration:
- Both the pH meter and the conductivity meter were calibrated with standard buffers or conductivity standards, respectively, prior to use.
- Zeta potential:
- -67.5 mV
- St. dev.:
- 0.9 mV
- pH:
- 11
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -50.3 mV
- St. dev.:
- 1.7 mV
- pH:
- 10
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -33 mV
- St. dev.:
- 0.8 mV
- pH:
- 9
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 5.4 mV
- St. dev.:
- 2.4 mV
- pH:
- 8
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 16.3 mV
- St. dev.:
- 3.6 mV
- pH:
- 7
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 16.3 mV
- St. dev.:
- 3.1 mV
- pH:
- 6
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 28.2 mV
- St. dev.:
- 0.4 mV
- pH:
- 5
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 20.8 mV
- St. dev.:
- 1.7 mV
- pH:
- 4
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 27.6 mV
- St. dev.:
- 1.7 mV
- pH:
- 3
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 11.4 mV
- St. dev.:
- 0.9 mV
- pH:
- 2
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -6.5 mV
- St. dev.:
- 0.9 mV
- pH:
- 1
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Isoelectric Point:
- 7.5
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Remarks on result:
- other: no St.dev. was stated
- Conclusions:
- The test item G6-3 has an approximate isoelectric point of 7.5 in a dispersion (0.01% w/w) in 10-3 M KCl in deionised water.
The point at which the curve crosses a zeta potential value of 0 mV is known as the isoelectric point, where the particles effectively carry no net electrical charge.
Conductivity measurements obtained for each sample remained fairly consistent from pH 4 to pH 11, which is an important property for zeta potential measurement. Below pH 4, conductivity was found to increase markedly, likely due to the substantial amounts of HCl needed in order to reach the low pH values. As a result, the concentration of TiO2 also decreased substantially in this pH range. In addition, the composition of each of the samples is not known. It is often found that TiO2 is coated with e.g. Al2O3 or ZrO2 which, especially in the case of Al2O3 exhibit increased solubility at pH values > pH 10. It is therefore strongly noted that data points below pH 4 and above pH 10 are unreliable in comparison to the rest of the data set.
- Reason / purpose for cross-reference:
- reference to same study
Reference
- Endpoint:
- nanomaterial Zeta potential
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 2019-05-17 to 2019-08-01
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- study well documented, meets generally accepted scientific principles, acceptable for assessment
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Sample TiO2 dispersion at 0.01% w/w was prepared by adding 20 mg of sample TiO2 powder to a stirring solution of 200 ml 10-3 M KCl in deionised water. To ensure dispersion, the solution was then stirred under shear for 1 minute at 2500 rpm.
The pH was then adjusted to pH 11 by addition of 0.01 M NaOH in deionised water. The conductivity was recorded, and a sample was taken for zeta potential measurement. The pH was lowered by 1 pH value by addition of 0.01 M HCl in deionised water, and the conductivity and zeta potential were recorded. This process was repeated to obtain final conductivity and zeta potential measurements across the pH range from pH 11 to pH 1. - GLP compliance:
- no
- Type of method:
- other: Dynamic light scattering (DLS), and pH meter and conductivity meter
- Sampling:
- please refer to `Principle of method of other than guideline´
- Specific details on test material used for the study:
- Product name: Sample G8-2
Appearance: white odourless powder
Substance stability: Stable under normal conditions
Substance humidity: 0.6 - Instruments:
- - Magnetic stirrer plate
- Silverson L5 mixer
- Conductivity and pH were measured using a Mettler Toledo Five Easy pH Meter F20-Std-Kit.
- Zeta potential was measured using a Horiba SZ-100 particle sizer. - Calibration:
- Both the pH meter and the conductivity meter were calibrated with standard buffers or conductivity standards, respectively, prior to use.
- Zeta potential:
- -61.4 mV
- St. dev.:
- 0.5 mV
- pH:
- 11
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -13.8 mV
- St. dev.:
- 3 mV
- pH:
- 10
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -55 mV
- St. dev.:
- 1.6 mV
- pH:
- 9
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -37.1 mV
- St. dev.:
- 3.6 mV
- pH:
- 8
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -52.8 mV
- St. dev.:
- 1.2 mV
- pH:
- 7
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -30.8 mV
- St. dev.:
- 3 mV
- pH:
- 6
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -46.5 mV
- St. dev.:
- 0.9 mV
- pH:
- 5
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -18.6 mV
- St. dev.:
- 1.9 mV
- pH:
- 4
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -2.6 mV
- St. dev.:
- 0.9 mV
- pH:
- 3
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 1.2 mV
- St. dev.:
- 1.9 mV
- pH:
- 2
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -3.2 mV
- St. dev.:
- 17.5 mV
- pH:
- 1
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Isoelectric Point:
- 2.5
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Remarks on result:
- other: no St.dev. was stated
- Conclusions:
- The test item G8-2 has an approximate isoelectric point of 2.5 in a dispersion (0.01% w/w) in 10-3 M KCl in deionised water.
The point at which the curve crosses a zeta potential value of 0 mV is known as the isoelectric point, where the particles effectively carry no net electrical charge.
Conductivity measurements obtained for each sample remained fairly consistent from pH 4 to pH 11, which is an important property for zeta potential measurement. Below pH 4, conductivity was found to increase markedly, likely due to the substantial amounts of HCl needed in order to reach the low pH values. As a result, the concentration of TiO2 also decreased substantially in this pH range. In addition, the composition of each of the samples is not known. It is often found that TiO2 is coated with e.g. Al2O3 or ZrO2 which, especially in the case of Al2O3 exhibit increased solubility at pH values > pH 10. It is therefore strongly noted that data points below pH 4 and above pH 10 are unreliable in comparison to the rest of the data set.
- Reason / purpose for cross-reference:
- reference to same study
Reference
- Endpoint:
- nanomaterial Zeta potential
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 2019-05-17 to 2019-08-01
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- study well documented, meets generally accepted scientific principles, acceptable for assessment
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Reason / purpose for cross-reference:
- reference to same study
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Sample TiO2 dispersion at 0.01% w/w was prepared by adding 20 mg of sample TiO2 powder to a stirring solution of 200 ml 10-3 M KCl in deionised water. To ensure dispersion, the solution was then stirred under shear for 1 minute at 2500 rpm.
The pH was then adjusted to pH 11 by addition of 0.01 M NaOH in deionised water. The conductivity was recorded, and a sample was taken for zeta potential measurement. The pH was lowered by 1 pH value by addition of 0.01 M HCl in deionised water, and the conductivity and zeta potential were recorded. This process was repeated to obtain final conductivity and zeta potential measurements across the pH range from pH 11 to pH 1. - GLP compliance:
- no
- Type of method:
- other: Dynamic light scattering (DLS), and pH meter and conductivity meter
- Sampling:
- please refer to `Principle of method of other than guideline´
- Specific details on test material used for the study:
- Product name: Sample G10-4
Appearance: white odourless powder
Substance stability: Stable under normal conditions
Substance humidity: 0.4 - Instruments:
- - Magnetic stirrer plate
- Silverson L5 mixer
- Conductivity and pH were measured using a Mettler Toledo Five Easy pH Meter F20-Std-Kit.
- Zeta potential was measured using a Horiba SZ-100 particle sizer. - Calibration:
- Both the pH meter and the conductivity meter were calibrated with standard buffers or conductivity standards, respectively, prior to use.
- Zeta potential:
- -37.3 mV
- St. dev.:
- 11.1 mV
- pH:
- 11
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -31.9 mV
- St. dev.:
- 3.4 mV
- pH:
- 10
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -21.3 mV
- St. dev.:
- 1.1 mV
- pH:
- 9
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -18.3 mV
- St. dev.:
- 2 mV
- pH:
- 8
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -16.2 mV
- St. dev.:
- 0.4 mV
- pH:
- 7
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 19.2 mV
- St. dev.:
- 9.4 mV
- pH:
- 6
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -6.7 mV
- St. dev.:
- 1.8 mV
- pH:
- 5
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 12.2 mV
- St. dev.:
- 2.6 mV
- pH:
- 4
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 29 mV
- St. dev.:
- 2.6 mV
- pH:
- 3
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 11.2 mV
- St. dev.:
- 0.9 mV
- pH:
- 2
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -0.2 mV
- St. dev.:
- 2.7 mV
- pH:
- 1
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Isoelectric Point:
- 6
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Remarks on result:
- other: no St.dev. was stated
- Conclusions:
- The test item G10-4 has an approximate isoelectric point of 6.0 in a dispersion (0.01% w/w) in 10-3 M KCl in deionised water.
The point at which the curve crosses a zeta potential value of 0 mV is known as the isoelectric point, where the particles effectively carry no net electrical charge.
Conductivity measurements obtained for each sample remained fairly consistent from pH 4 to pH 11, which is an important property for zeta potential measurement. Below pH 4, conductivity was found to increase markedly, likely due to the substantial amounts of HCl needed in order to reach the low pH values. As a result, the concentration of TiO2 also decreased substantially in this pH range. In addition, the composition of each of the samples is not known. It is often found that TiO2 is coated with e.g. Al2O3 or ZrO2 which, especially in the case of Al2O3 exhibit increased solubility at pH values > pH 10. It is therefore strongly noted that data points below pH 4 and above pH 10 are unreliable in comparison to the rest of the data set.
Data source
Reference
- Reference Type:
- study report
- Title:
- Unnamed
- Year:
- 2 019
- Report date:
- 2019
Materials and methods
Test guideline
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Sample TiO2 dispersion at 0.01% w/w was prepared by adding 20 mg of sample TiO2 powder to a stirring solution of 200 ml 10-3 M KCl in deionised water. To ensure dispersion, the solution was then stirred under shear for 1 minute at 2500 rpm.
The pH was then adjusted to pH 11 by addition of 0.01 M NaOH in deionised water. The conductivity was recorded, and a sample was taken for zeta potential measurement. The pH was lowered by 1 pH value by addition of 0.01 M HCl in deionised water, and the conductivity and zeta potential were recorded. This process was repeated to obtain final conductivity and zeta potential measurements across the pH range from pH 11 to pH 1. - GLP compliance:
- no
- Type of method:
- other: Dynamic light scattering (DLS), and pH meter and conductivity meter
- Sampling:
- please refer to `Principle of method of other than guideline´
Test material
- Reference substance name:
- Titanium dioxide
- EC Number:
- 236-675-5
- EC Name:
- Titanium dioxide
- Cas Number:
- 13463-67-7
- Molecular formula:
- O2Ti
- IUPAC Name:
- dioxotitanium
- Test material form:
- solid: particulate/powder
- Details on test material:
- Appearance: white odourless powder
Relative density: ~ 3.9
Constituent 1
- Specific details on test material used for the study:
- Product name: Sample G1-1
Substance stability: Stable under normal conditions
Substance humidity: 0.9
Data gathering
- Instruments:
- - Magnetic stirrer plate
- Silverson L5 mixer
- Conductivity and pH were measured using a Mettler Toledo Five Easy pH Meter F20-Std-Kit.
- Zeta potential was measured using a Horiba SZ-100 particle sizer. - Calibration:
- Both the pH meter and the conductivity meter were calibrated with standard buffers or conductivity standards, respectively, prior to use.
Results and discussion
Zeta potentialopen allclose all
- Zeta potential:
- -40.4 mV
- St. dev.:
- 5.8 mV
- pH:
- 11
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -40.2 mV
- St. dev.:
- 2.3 mV
- pH:
- 10
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -44.3 mV
- St. dev.:
- 0.9 mV
- pH:
- 9
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -32.5 mV
- St. dev.:
- 1.5 mV
- pH:
- 8
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -22.6 mV
- St. dev.:
- 0.4 mV
- pH:
- 7
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -27.1 mV
- St. dev.:
- 10 mV
- pH:
- 6
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -16.6 mV
- St. dev.:
- 2.1 mV
- pH:
- 5
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 22.5 mV
- St. dev.:
- 0.6 mV
- pH:
- 4
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 23.6 mV
- St. dev.:
- 1 mV
- pH:
- 3
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- 6.7 mV
- St. dev.:
- 1 mV
- pH:
- 2
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Zeta potential:
- -8.3 mV
- St. dev.:
- 5.3 mV
- pH:
- 1
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
Isoelectric point
- Isoelectric Point:
- 4.5
- Medium:
- TiO2 dispersion (0.01% w/w) in 10-3 M KCl in deionised water
- Remarks on result:
- other: no St.dev. was stated
Any other information on results incl. tables
The point at which the curve crosses a zeta potential value of 0 mV is known as the isoelectric point, where the particles effectively carry no net electrical charge.
Conductivity measurements obtained for each sample remained fairly consistent from pH 4 to pH 11, which is an important property for zeta potential measurement. Below pH 4, conductivity was found to increase markedly, likely due to the substantial amounts of HCl needed in order to reach the low pH values. As a result, the concentration of TiO2 also decreased substantially in this pH range. In addition, the composition of each of the samples is not known. It is often found that TiO2 is coated with e.g. Al2O3 or ZrO2 which, especially in the case of Al2O3 exhibit increased solubility at pH values > pH 10. It is therefore strongly noted that data points below pH 4 and above pH 10 are unreliable in comparison to the rest of the data set.
Applicant's summary and conclusion
- Conclusions:
- The test item G1-1 has an approximate isoelectric point of 4.5 in a dispersion (0.01% w/w) in 10-3 M KCl in deionised water.
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