3.4 Purification of VOCs

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From the course by The Hong Kong University of Science and Technology

Introduction to Indoor Air Quality

39 ratings

The Hong Kong University of Science and Technology

Introduction to Indoor Air Quality

39 ratings

Course Overview: https://youtu.be/LLVb4FOn4uU This course provides a basic knowledge of an emerging area – Indoor Air Quality (IAQ) in buildings. Learners will realize the importance of maintaining proper IAQ. Characteristics associated with indoor air contaminants (IAC) are demonstrated, such as • Particulate matters (PM2.5, PM10) • Radon • Volatile organic compounds (VOCs) • Asbestos • Bio-aerosols, and more Safe exposure levels, resulting health effects, measurement techniques, mitigate and control measures of these IAC are discussed. Other important areas related to IAQ such as building ventilation systems, indoor flow characteristics, sick building syndrome, and thermal comfort are also covered in this course.

From the lesson

VOCs, Ozone and Combustion Related Pollutants

In this module, three other major Indoor Air Contaminants that can easily be found at home and office. - (1) Volatile Organic Compounds (VOCs), (2) Ozone and (3) Combustion related Air Contaminants (i.e., Carbon Monoxide and Nitrogen Dioxide) are introduced.

3.1 Introduction to VOCs4:10

3.2 Two common VOCs - Formaldehyde and Tetrachloroethylene5:20

3.3 Measuring VOCs5:44

3.4 Purification of VOCs3:56

3.5 Semi VOCs4:28

Meet the Instructors

Christopher Chao
Adjunct Professor
Department of Mechanical and Aerospace Engineering

Hello everyone.

In this video,

we look into VOCs Purification Technologies.

In order to reduce indoor VOCs concentration,

these VOCs Purification Technologies can be applied.

Let's talk about each of them.

Adsorption is a process in which VOCs are attracted to the surface of solid or liquid,

such that VOCs are separated from the air.

The adsorping material is called adsorbent.

Activated carbon is the most common adsorbent for VOCs.

Other adsorbents include silica gel,

alumina, zeolite, and mobile composition of matter - MCM41.

Absorption is a process involving bulk penetration of gases

into the structure of the solid or liquid by means of diffusion.

Common absorbents are water,

caustic soda, amins and low volatility hydrocarbons.

Photocatalytic Oxidation, PCO in short,

is another air purifying technique.

This technique removes lighter VOCs that are not effectively absorbed on carbon.

PCO is a process of shining ultraviolet light on to a catalytic surface.

The surface has a titanium oxide surface coating.

And then, highly reactive electrons are created.

These electrons react with VOCs and eventually,

convert them into harmless substances,

such as CO2 and water.

Biofiltration is an alternative for

low concentration gas streams because of its low energy consumption,

relatively moderate operating costs and minimal generation of byproducts.

Biofilters remove VOCs by naturally occurring microorganisms.

Microorganisms consume VOCs for growth.

To facilitate the growth and metabolism of the microorganisms,

a controlled environment with specific temperature and humidity level is required.

The temperature requirement varies for different microorganisms,

from around 20 degrees Celsius to 45 degrees Celsius.

We can also reduce indoor VOC concentration by chemical filters.

Chemical filters use chemical oxidants,

such as hydrogen peroxide,

sodium hypochlorite, or potassium permanganate to eliminate VOCs.

The speed of the elimination process depends

on the oxidation reduction potential of the reaction.

Reaction can be split up by using an inorganic catalyst,

such as iron for peroxide,

nickel for chlorine, or enzymes,

which is an organic catalyst.

To conclude, in this video,

we introduced several VOCs purification technologies.

Adsorption, Absorption, Photocatalytic oxidation,

biofiltration, and chemical filters.

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