Sun and photocatalysts will clean polluted water—cheaply and quickly

October 17, 2013, Institute of Physical Chemistry of the Polish Academy of Sciences
Sun and photocatalysts will clean polluted water--cheaply and quickly
Made of iron or chromium doped titanium dioxide, silica or zeolite supported photocatalysts from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw effectively clean water contaminated with phenol and cellulose. The picture shows Dr Juan Carlos Colmenares from the IPC PAS. Credit: IPC PAN, Grzegorz Krzyżewski

A little amount of appropriately prepared powder is poured in water polluted with phenol and cellulose. A bit of the sun and after fifteen minutes harmful compounds disappear, and the powder can be filtered off and reused. Sounds like a fairy tale? Perhaps, but it is not magic, only a masterly use of chemistry and physics by researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw.

Many areas worldwide are affected by the problem of growing water pollution by wastes from wood and paper industries, including and phenol derivatives. Removal of these agents from water can be easier in future due to low cost and easy-to-produce developed by Dr Juan Carlos Colmenares' group from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw.

Catalysts are substances that participate in the , speed their courses and (almost) fully recover after the reactions are completed. In typical catalytic processes the catalysts must be activated at high temperatures, typically of several hundred degrees centigrade, often at a significantly increased pressure.

The photocatalysts designed and synthesised at the IPC PAS are much less demanding. They are activated by solar or UV light, and the actual chemical reaction can take place at a temperature of about 30°C and under normal pressure. Such conditions naturally occur in many places on Earth.

The crucial component of the new photocatalysts is titanium dioxide doped with small amount of iron or atoms. All these are commonly available and cheap. The photocatalysts are deposited on appropriate supports – silica grains or zeolites (aluminosilicates) – using common laboratory equipment: a rotary evaporator and an ultrasonic bath.

"Ultrasonic irradiation of a solution containing precursors of titania and chromium or iron generates microbubbles of high pressure and temperature. We can manage these conditions and prepare nanocomposite materials which are very stable", explains Dr Colmenares.

Chromium or iron doped catalytic materials so prepared have been studied and characterised in detail at the Institute of Physical Chemistry of the PAS and by the Prof. Krzysztof Kurzydłowski's research group from the Faculty of Materials Science and Engineering, Warsaw University of Technology.

How do the new photocatalysts clean water? In laboratory conditions the process takes only 15-20 minutes and consists in pouring powder with photocatalyst in water. Then, short exposure to solar radiation is sufficient to make disappear water polluting cellulose or phenol derivatives.

Silica supported photocatalysts turned out to be particularly effective in phenol removal, leading to a high degree of phenol oxidation and yielding water and carbon dioxide as the reaction products. Zeolite supported systems catalysed glucose partial degradation (glucose is a monomer, and thus a basic "brick" forming cellulose polymer chains) resulting in formation of, e.g., gluconic and glucaric acids, important carboxylic acids used in food, pharmaceutical and cosmetic industries.

What's particularly important is that the analyses performed by Dr Colmenares' group clearly prove that there is no release of chromium or iron atoms to water during the entire cleaning process.

After the reaction is completed, the photocatalyst can be easily recovered. Due to durable deposition on silica or zeolite particles of relatively large (micrometric) size, it's enough to filter water to get the catalyst back. The recovered powder can be reused, and multiple repetition of the cycle does not significantly affect the catalyst performance.

The new catalysts can also be used outside the industry. Coatings manufactured of these materials have sufficient mechanical strength to be used, e.g., as swimming pool accessories. With good solar insolation, water in a swimming pool constructed with the use of such materials would be subject to continuous self-cleaning process.

"Essential advantages of our photocatalysts include simplicity of production, low manufacturing costs and convenience of performing chemical reactions under natural conditions. Equally important is that our materials allow to stop oxidizing pollutants at desired stage and to obtain substances important for the industry", stresses Dr Colmenares.

Explore further: New method to clean and treat polluted water for extraction of chemicals

Provided by: Institute of Physical Chemistry of the Polish Academy of Sciences


Related Stories

Unexpected behavior of well-known catalysts

June 19, 2013

Industrial palladium-copper catalysts change their structures before they get to work, already during the activation process. As a result, the reaction is catalysed by a catalyst that is different from the one originally ...

Producing hydrogen from water with carbon / charcoal powder

August 28, 2013

In the latest advance in efforts to find an inexpensive way to make hydrogen from ordinary water—one of the keys to the much-discussed "hydrogen economy"—scientists are reporting that powder from high-grade charcoal and ...

Recommended for you

Bio-renewable process could help 'green' plastic

January 19, 2018

When John Wesley Hyatt patented the first industrial plastic in 1869, his intention was to create an alternative to the elephant tusk ivory used to make piano keys. But this early plastic also sparked a revolution in the ...

Simulations show how atoms behave inside self-healing cement

January 19, 2018

Researchers at Pacific Northwest National Laboratory (PNNL) have developed a self-healing cement that could repair itself in as little as a few hours. Wellbore cement for geothermal applications has a life-span of only 30 ...

Looking to the sun to create hydrogen fuel

January 18, 2018

When Lawrence Livermore scientist Tadashi Ogitsu leased a hydrogen fuel-cell car in 2017, he knew that his daily commute would change forever. There are no greenhouse gases that come out of the tailpipe, just a bit of water ...

A new polymer raises the bar for lithium-sulfur batteries

January 18, 2018

Lithium-sulfur batteries are promising candidates for replacing common lithium-ion batteries in electric vehicles since they are cheaper, weigh less, and can store nearly double the energy for the same mass. However, lithium-sulfur ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.