ISO/TR 23015:2020

TECHNICAL ISO/TR
REPORT 23015
First edition
2020-08
Fine bubble technology —
Measurement technique matrix for
the characterization of fine bubbles
Technologie des fines bulles — Matrice de méthodes de mesure pour
la caractérisation des fines bulles
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 1
5 Fine bubble characterization . 1
5.1 General . 1
5.2 Comparison of size and concentration indices from different sources . 2
6 Characterization techniques . 3
6.1 Dynamic light scattering . 3
6.1.1 General. 3
6.1.2 Reference standard . 3
6.1.3 Size . 3
6.1.4 Size distribution . 4
6.1.5 Concentration . 4
6.1.6 Measurement time . 4
6.2 Methods for Zeta potential determination (electrophoretic mobility) . 4
6.2.1 General. 4
6.2.2 Reference standard . 4
6.2.3 Charge . 4
6.2.4 Zeta distribution . 4
6.2.5 Concentration . 4
6.2.6 Measurement time . 4
6.3 Particle tracking analysis method . 5
6.3.1 General. 5
6.3.2 Reference standards . 5
6.3.3 Size . 5
6.3.4 Size distribution . 5
6.3.5 Concentration . 5
6.3.6 Measurement time . 6
6.4 Laser diffraction methods . 6
6.4.1 General. 6
6.4.2 Reference standard . 6
6.4.3 Size . 6
6.4.4 Concentration . 6
6.4.5 Measurement time . 6
6.5 Resonant mass measurement . 6
6.5.1 General. 6
6.5.2 Reference standard . 7
6.5.3 Size . 7
6.5.4 Size distribution . 7
6.5.5 Concentration . 7
6.5.6 Measurement time . 7
6.6 Electrical sensing zone method . 7
6.6.1 General. 7
6.6.2 Reference standard . 7
6.6.3 Size . 7
6.6.4 Size distribution . 7
6.6.5 Concentration . 8
6.6.6 Measurement time . 8
6.7 Ultrasonic attenuation spectroscopy . 8
6.7.1 General. 8
6.7.2 Reference standard . 8
6.7.3 Size . 8
6.7.4 Size distribution . 8
6.7.5 Concentration . 8
6.7.6 Measurement time . 8
6.8 Single particle light interaction methods . 8
6.8.1 General. 8
6.8.2 Reference standards . 9
6.8.3 Size . 9
6.8.4 Size distribution . 9
6.8.5 Concentration . 9
6.8.6 Measurement time . 9
6.9 Static image analysis method . 9
6.9.1 General. 9
6.9.2 Reference standard . 9
6.9.3 Size . 9
6.9.4 Size distribution . 9
6.9.5 Concentration .10
6.9.6 Measurement time .10
6.10 Dynamic image analysis methods .10
6.10.1 Reference standard .10
6.10.2 Size .10
6.10.3 Size distribution .10
6.10.4 Concentration .10
6.10.5 Measurement time .10
6.11 Static multiple light scattering (SMLS).10
6.11.1 General.10
6.11.2 Reference standard .11
6.11.3 Size .11
6.11.4 Size distribution .11
6.11.5 Concentration .11
6.11.6 Measurement time .11
Bibliography .12
iv © ISO 2020 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 281, Fine bubble technology.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
Introduction
Fine bubble technology has numerous applications across industries such as cleaning, transport,
maintenance, agriculture, aquaculture, food and drink, cosmetics as well as biomedical. The detection,
characterization and quantification of properties of fine bubble mixtures are central to the development
of this horizontal general purpose technology.
A number of techniques used for particle detection and characterization may be applicable to the
characterization of fine bubble mixtures in liquids. Some techniques may have a number of special
sample handling, sample preparation or equipment settings to yield quantifiable and reliable results.
This document lists a number of techniques and discusses their applicability for the characterization
of fine bubble mixtures as well as their limitations. Fine bubbles are able to exist in opaque liquids
or liquids of high viscosity. Some fine bubble samples are turbid due to a large number of bubbles. All
fine bubble samples are dynamic in nature and their properties change with time. For this reason, the
acquisition time of each technique is of great relevance. Most fine bubble samples contain particles as
well as fine bubbles. Distinguishing particles and bubbles and then additionally characterizing them by
size and number or vice-versa may not be possible with all particle characterization equipment.
vi © ISO 2020 – All rights reserved

TECHNICAL REPORT ISO/TR 23015:2020(E)
Fine bubble technology — Measurement technique matrix
for the characterization of fine bubbles
1 Scope
This document focuses on listing most commonly used preparation and characterization techniques for
fine bubbles and their interpretation. The merits and limitations of each of the techniques are outlined.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Abbreviated terms
CCD Charge coupled device
DLS Dynamic light scattering
EZ Electrical sensing zone method
LD Laser diffraction methods
PSD Particle size distribution
PTA Particle tracking analysis method
RMM Resonance mass measurement
SPOS Single particle light interaction methods
SMLS Static multiple light scattering
USS Ultrasonic attenuation spectroscopy
ZP Methods for Zeta-potential determination
5 Fine bubble characterization
5.1 General
A number of general particle counting and sizing techniques are available commercially. Some of them
are applicable for the characterization of fine bubble dispersions and ultrafine bubble dispersions. Such
dispersions may be in liquid of any kind. Some liquids may not be transparent (e.g. printer ink) or stable
(e.g. flammable fuel). This document refers to a selection of commercially available techniques and
evaluates their applicability and their limitations.
The parameters of interest are as follows.
— Fine bubble size – This usually refers to the equivalent hydrodynamic diameter but could be different
depending on the techniques.
— Fine bubble size distribution – For the purpose of this document, this is the number-size (or
equivalent) distribution.
— Number concentration – The total number (or equivalent) of bubbles per unit volume.
— Measurement time – The time to complete data acquisition.
5.2 Comparison of size and concentration indices from different sources
Consideration should be given when different techniques are being compared, that each technique
measures a different physical property of the sample. In deriving size and/or concentration indices
from different techniques, it should be anticipated that results will demonstrate differences in value
but they will likely show trend and/or correlate.
Care should be taken when comparing size and concentration indices. Even if the same technique is used,
the method from example two laser diffraction machines will need to be checked to verify parameters
such as measurement time, analysis models and pump rate. Table 1 provides a quick reference for the
typical size and concentration indices of different techniques in the measurement of bubbles.
Table 1 — Quick-use-matrix
Bubble measurands
Number
International
Size concentra- Measure-
Techniques
Standard
Size distribu- tion ment
tion (bubbles time
per ml)
5 nm - Intensity- Typical
Dynamic light scattering DLS ISO 22412 > 10
10 μm based 5 min
Methods for Zeta-potential
ZP ISO 13099-2 < 5 min
determination
50 nm – Number-
b 7 9
Particle tracking analysis method PTA ISO 19430 10 - 10 ~5 min
1 000 nm based
100 nm – Volume-
Laser diffraction methods LD ISO 13320 0,000 1 % ms - 10 s
3 mm based
7 9
10 - 10
micro-
a
s
...