ISO 22197-1:2007

INTERNATIONAL ISO
STANDARD 22197-1
First edition
2007-09-01

Fine ceramics (advanced ceramics,
advanced technical ceramics) — Test
method for air-purification performance
of semiconducting photocatalytic
materials —
Part 1:
Removal of nitric oxide
Céramiques techniques — Méthodes d'essai relatives à la performance
des matériaux photocatalytiques semi-conducteurs pour la purification
de l'air —
Partie 1: Élimination de l'oxyde nitrique




Reference number
ISO 22197-1:2007(E)
©
ISO 2007

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ISO 22197-1:2007(E)
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ISO 22197-1:2007(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Symbols . 3
5 Principle. 3
6 Apparatus . 3
7 Test piece . 6
8 Procedure . 6
9 Calculation. 8
10 Test report . 10
Annex A (informative) Results of round-robin test. 11
Bibliography . 12

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ISO 22197-1:2007(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 22197-1 was prepared by Technical Committee ISO/TC 206, Fine ceramics.
ISO 22197 consists of the following parts, under the general title Fine ceramics (advanced ceramics,
advanced technical ceramics) — Test method for air-purification performance of semiconducting photocatalytic
materials:
⎯ Part 1: Removal of nitric oxide
The following parts are under preparation:
⎯ Part 2: Removal of acetaldehyde
⎯ Part 3: Removal of toluene

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INTERNATIONAL STANDARD ISO 22197-1:2007(E)

Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for air-purification performance
of semiconducting photocatalytic materials —
Part 1:
Removal of nitric oxide
1 Scope
This part of ISO 22197 specifies a test method for the determination of the air-purification performance of
materials that contain a photocatalyst or have photocatalytic films on the surface, usually made from
semiconducting metal oxides, such as titanium dioxide or other ceramic materials, by continuous exposure of
a test piece to the model air pollutant under illumination with ultraviolet light. This part of ISO 22197 is
intended for use with different kinds of materials, such as construction materials in flat sheet, board or plate
shape, that are the basic forms of materials for various applications. This part of ISO 22197 also applies to
materials in honeycomb-form, and to plastic or paper materials if they contain ceramic microcrystals and
composites. This part of ISO 22197 does not apply to powder or granular photocatalytic materials.
This test method is usually applicable to photocatalytic materials produced for air purification. This method is
not suitable for the determination of other performance attributes of photocatalytic materials, i.e.,
decomposition of water contaminants, self-cleaning, antifogging and antibacterial actions. It concerns the
removal of nitric oxide.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 31-0:1992, Quantities and units — Part 0: General principles
ISO 4677-1:1985, Atmospheres for conditioning and testing — Determination of relative humidity — Part 1:
Aspirated psychrometer method
1)
ISO 4892-1:— , Plastics — Methods of exposure to laboratory light sources — Part 1: General guidance
ISO 4892-3:2006, Plastics — Methods of exposure to laboratory light sources — Part 3: Fluorescent UV
lamps
ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic
method for the determination of repeatability and reproducibility of a standard measurement method
ISO 6145-7:2001, Gas analysis — Preparation of calibration gas mixtures using dynamic volumetric
methods — Part 7: Thermal mass-flow controllers

1) To be published. (Revision of ISO 4892-1:1999.)
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ISO 22197-1:2007(E)
ISO 7996:1985, Ambient air — Determination of the mass concentration of nitrogen oxides —
Chemiluminescence method
2)
ISO 10304-1:— , Water quality — Determination of dissolved anions by liquid chromatography of ions —
Part 1: Determination of bromide, chloride, fluoride, nitrate, nitrite, phosphate and sulfate
ISO 10523:1994, Water quality — Determination of pH
ISO/IEC 17025:2005, General requirements for the competence of testing and calibration laboratories
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
photocatalyst
substance that performs one or more functions based on oxidation and reduction reactions under
photoirradiation, including decomposition and removal of air and water contaminants, deodorization, and
antibacterial, self-cleaning and antifogging actions
3.2
photocatalytic materials
materials in which or on which the photocatalyst is added by coating, impregnation, mixing, etc.
NOTE Such photocatalytic materials are intended primarily for use as building and road construction materials to
obtain the above-mentioned functions.
3.3
zero-calibration gas
air that does not contain pollutants (i.e. in which common pollutants are below 0,01 µl/l)
NOTE The zero-calibration gas is prepared from indoor air using a laboratory air-purification system, or supplied as
synthetic air in a gas cylinder.
3.4
standard gas
diluted gases of known concentrations supplied in cylinders and certified by an accredited laboratory
3.5
test gas
mixture of air and pollutant(s) of known concentration prepared from a standard gas or a zero-calibration gas,
to be used for the performance test of a photocatalytic material
3.6
purified water
water to be used for elution, etc., with a conductivity lower than 1 µS, prepared by the ion exchange method or
distillation

2) To be published. (Revision of ISO 10304-1:1992.)
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ISO 22197-1:2007(E)
4 Symbols
f air-flow rate converted into that at the standard state (0 °C, 101,3 kPa, and dry gas basis) (l/min)
φ nitric oxide volume fraction at the reactor exit (µl/l)
NO
φ supply volume fraction of nitric oxide (µl/l)
NO
i
φ nitrogen dioxide volume fraction at the reactor exit (µl/l)
NO
2
φ the volume fraction of nitrogen oxides (φ + φ ) at the reactor exit (µl/l)
NO NO NO
x 2
ρ nitrite ion concentration in the eluent from the test piece (mg/l)
NO
2-
ρ nitrate ion concentration in the eluent from the test piece (mg/l)
NO
3-
t time of adsorption, removal or desorption operation (min)
n the amount of NO adsorbed by the test piece (µmol)
ads x
n the amount of NO desorbed from the test piece (µmol)
des x
n the amount of NO removed by the test piece (µmol)
NO
n the amount of NO formed by the test piece (µmol)
NO 2
2
n the amount of NO removed by the test piece (µmol)
NO x
x
n the amount of nitrogen eluted from the test piece (µmol) [w , w are the 1st and 2nd elutions,
w 1 2
respectively]
V the volume of collected washings (ml) [w , w are the 1st and 2nd elutions, respectively]
w 1 2
η the fractional recovery of nitrogen
w
5 Principle
This part of ISO 22197 concerns the development, comparison, quality assurance, characterization, reliability,
[1]
and design data generation of photocatalytic materials . The method described is intended to obtain the air-
purification performance of photocatalytic materials by exposing a test piece to model polluted air under
[2]
illumination by ultraviolet (UV) light . Nitric oxide (NO) is chosen as a typical air pollutant that gives
nonvolatile products on the photocatalyst. The test piece, placed in a flow-type photoreactor, is activated by
[3]
UV illumination, and adsorbs and oxidizes gas-phase NO to form nitric acid (or nitrate) on its surface . A part
of the NO is converted to nitrogen dioxide (NO ) on the test piece. The air-purification performance is
2
determined from the amount of the net removal of nitrogen oxides (NO ) (= NO removed – NO formed). The
x 2
simple adsorption and desorption of NO by the test piece (not due to photocatalysis) is evaluated by tests in
the dark. Although the photocatalytic activity is reduced by the accumulation of reaction products, it is usually
[4]
restored by washing with water . The elution test provided here gives information about the ease of
regeneration and material balance of the pollutants.
6 Apparatus
6.1 Test equipment
The test equipment enables a photocatalytic material to be examined for its pollutant-removal capability by
supplying the test gas continuously, while providing photoirradiation to activate the photocatalyst. It consists of
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ISO 22197-1:2007(E)
a test gas supply, a photoreactor, a light source, and pollutant measurement equipment. Since low
concentrations of pollutants are to be tested, the system shall be constructed with materials of low adsorption
and resistant to ultraviolet (UV) radiation, for example, acrylic resin, stainless steel, glass and fluorocarbon
polymers. An example of a test system is shown in Figure 1.
6.2 Test gas supply
The test gas supply provides air polluted with the model contaminant at a predetermined concentration,
temperature and humidity, and supplies it continuously to the photoreactor. It consists of flow regulators, a
humidifier, gas mixers, etc. The flow rate of each gas should be within 5 % of the designated value, which is
easily attained by using thermal mass-flow controllers, with a knowledge of calibrated gas flow rate and
temperature in accordance with ISO 6145-7. Typical capacities of the flow controller for pollutant gas, dry air
and wet air are 0,1 l/min, 2,0 l/min and 2,0 l/min, respectively. The expression of gas flow rate in this part of
ISO 22197 is that converted to the standard state (0 °C, 101,3 kPa, and dry gas basis). The standard NO gas,
normally balanced with nitrogen in a cylinder, shall have a volume fraction of 30 to 100 µl/l, because the
oxidation of NO to NO upon mixing with purified air becomes prominent with a higher concentration of NO.
2
Dimensions in millimetres

Key
1 light source 7 mass-flow controllers
2 optical window 8 gas mixers
3 test piece 9 humidifier
4 standard gas (pollutant) 10 analyser
5 air-purification system 11 vent
6 air compressor
Figure 1 — A schematic of the test equipment

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ISO 22197-1:2007(E
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