Industrial wastewater from manufacturing processes is a significant environmental challenge worldwide. Many industrial effluents contain persistent pollutants – chemicals that conventional water treatment plants struggle to remove completely[1]. These include substances like pesticides, pharmaceutical residues, industrial chemicals, microplastics, dyes, and even the notorious “forever chemicals” PFAS[2]. For example, a recent report by the German Environment Agency found traces of 40 different pharmaceutical compounds in drinking water by 2023[3], with even higher levels in groundwater and surface waters. Such contaminants can accumulate in ecosystems, posing risks to wildlife and human health. There is a pressing need for advanced treatment technologies that can break down these hard-to-remove pollutants into harmless end products, ensuring clean water for the environment and society.
The
Challenge of Persistent Pollutants in Water
Even in developed countries with modern sewage infrastructure, trace
contaminants continue to slip through into the water cycle[2].
Traditional treatment methods – like biological digestion, filtration, or
chemical dosing – often reach their technical or economic limits when dealing
with trace-level industrial chemicals. Many pollutants are bio-refractory,
meaning they resist biological breakdown, or they require prohibitively
expensive processes to remove. For instance, PFAS (per- and polyfluoroalkyl
substances) are highly stable compounds used in coatings and firefighting
foams that conventional plants cannot fully eliminate. Similarly,
pharmaceutical residues and certain dyes can pass through treatment unchanged[1].
The result is that rivers and even drinking water sources have detectable
levels of these substances, raising concerns about long-term exposure. As
clean water is a fundamental human right, researchers have been searching for
more effective solutions to destroy pollutants rather than just capture
them.
One promising approach falls under advanced oxidation processes
(AOPs) – technologies that generate highly reactive species capable of
oxidizing (essentially “burning up”) organic pollutants. Among AOPs, photocatalytic
oxidation has gained attention for its ability to break down complex
molecules using only light, a catalyst, and oxygen, typically producing benign
end products like carbon dioxide, water, or mineral salts. Photocatalysis
involves shining light (often UV) on a semiconductor catalyst (commonly
titanium dioxide or similar materials), which excites electrons and generates
reactive radicals (like hydroxyl radicals) that attack organic pollutant
molecules. A key advantage of photocatalytic oxidation is that it can mineralize
pollutants – effectively decomposing them completely – without the need to add
aggressive chemicals. However, implementing photocatalysis in real wastewater
streams requires clever engineering to ensure the light, catalyst, and
pollutants efficiently interact at large scale.
Photocatalytic
Foam Ceramics: A New Solution
A research team at the Fraunhofer Institute for Ceramic Technologies
and Systems (IKTS) in Dresden, Germany, has developed an innovative
photocatalytic system using multifunctional ceramic foams as the
catalyst support[4][5].
These foam ceramics are porous, sponge-like ceramic structures coated
with photocatalyst materials and other functional layers. The
Fraunhofer-developed system shines UV light onto the coated foam, triggering
the formation of reactive radical species on the foam’s surfaces. When
contaminated water flows through the foam’s pores, the radicals oxidize the
organic pollutants, breaking them down efficiently into smaller, harmless
compounds[6].
Fraunhofer IKTS researchers have developed multifunctional foam
ceramics for photocatalytic purification of industrial wastewater. The foam's
highly porous, network-like structure provides an enormous surface area for
catalysts and allows deep penetration of UV light for efficient pollutant
breakdown[7].
According to Fraunhofer IKTS scientist Franziska Saft, exposing
the functionalized foam surfaces to ultraviolet light creates “highly
reactive radicals in the water, which decompose organic impurities”[6].
Importantly, Saft notes that this photocatalytic process “does not produce
any undesirable by-products, nor does it require additional oxidizing agents
such as ozone”[8].
In other words, the method avoids the formation of harmful secondary chemicals
and doesn’t need supplemental chemicals to work – the light-activated catalyst
alone does the job. This is a significant benefit over some conventional
treatments that might generate toxic by-products or rely on adding oxidants
(like chlorine or ozone) that can form residual pollution. By using light as
a clean energy source to drive reactions on the foam, the system remains chemical-free
and energy-efficient[4].
How the Foam
Ceramic Catalyst Works
The core of this technology is the ceramic foam material itself.
These foams are engineered to have a high open porosity (up to ~90%),
meaning most of the volume is empty space (pores) that water and light can pass
through[7]. The
foam’s solid framework is a web of ceramic struts, whose surfaces are coated
with photocatalyst nanoparticles and potentially other additives like
adsorbents. This design yields several advantages:
- Large Surface Area: The foam’s sponge-like architecture provides a vast surface
area within a compact volume[7].
Pollutant molecules in the water have many opportunities to come in
contact with a catalyst site on the foam walls. Even thin catalyst
coatings on the foam are enough to achieve high reaction rates because of
the sheer surface available[9].
As researcher Daniela Haase explains, the foam structure “allows
us to create a highly reactive surface area, enabling high catalytic
conversions even when only thin layers are applied to the foam ceramic”[9].
- Effective Light
Penetration: With porosity up to 90%, the foam is
mostly transparent to the UV light used. The open pores act as channels
that let light penetrate deep into the material[7].
This means even the inner surfaces of the foam receive illumination,
maximizing the usage of the catalyst throughout the volume. Traditional
photocatalytic reactors often use catalyst powders or coated flat
surfaces, where delivering light uniformly can be challenging; in
contrast, these foams ensure that light reaches all active sites in
their interior.
- Flow-Through Design: The foam is “flow-through,” meaning water can be pumped
directly through its porous network. As the contaminated water percolates
through the foam, it intimately contacts the catalyst-coated surfaces
under UV illumination. This three-way contact between pollutant,
catalyst, and light is crucial for efficient photocatalysis[10].
The Fraunhofer team emphasizes that maintaining good contact is key to
performance, and the foam naturally facilitates this by mixing the phases
(light and water) in its pores.
- Multifunctional
Coatings: Besides photocatalysts, the foam can be
coated with additional functional materials such as adsorbents or
co-catalysts. Adsorbent layers can capture pollutants and concentrate them
on the surface, increasing the local pollutant concentration for the
photocatalyst to destroy. Co-catalysts (like noble metals or other
semiconductors) can enhance the generation of radicals or broaden the
light absorption spectrum. The flexibility in coating composition means
the foam can be tuned to target specific contaminants or improve
efficiency. The challenge, as Haase notes, is ensuring these catalyst
coatings are stably anchored; they must resist being washed off
(leached) by the flowing water[9].
The research team has addressed this by developing durable coating methods
so that the catalysts remain fixed to the foam even under continuous flow
conditions.
Ceramic stack system developed at Fraunhofer IKTS, featuring a
multifunctional foam ceramic element paired with a UV LED light array for
photocatalytic water purification[11][12].
This compact setup can be integrated into industrial sites to treat wastewater
streams on-site, using energy-efficient UV-LEDs to activate the foam's catalyst
coatings.
Because the ceramic foam is robust and inorganic, it can withstand
harsh industrial conditions (e.g. high temperatures, extreme pH) better than
polymer filters or membranes. It’s also self-supporting – the foam acts as
both the reactor medium and the catalyst host, so there is no need for
separate catalyst slurry or cartridges that require replacement. Maintenance is
simplified, as the foam can potentially be cleaned and reused for long periods,
and any loss of activity could be restored by recoating the foam rather than
disposing of it.
On-Site Piloting
and Future Outlook
Fraunhofer IKTS’s photocatalytic foam system is not just a lab
experiment – it has already moved into pilot-scale trials with industry
partners. The researchers have developed complete compact water treatment
units that incorporate the foam ceramics, UV light sources, and tailored
reactor designs[11].
Notably, they are using modern UV-LED arrays instead of traditional
mercury UV lamps[13].
UV-LEDs are more energy-efficient, have longer lifespans, and contain no toxic
mercury, aligning well with the goal of sustainable operation. The entire
system is designed to be modular and scalable, meaning multiple foam
modules and LED units can be stacked or combined to handle larger flow rates as
needed[14].
An important aspect of Fraunhofer’s approach is integration into
existing industrial processes. The pilot units are being tested directly at
industrial sites – for example, at pharmaceutical companies, semiconductor
manufacturers, papermills, dairy producers, and textile factories[15]. These
are industries known to generate wastewater with hard-to-treat organic
contaminants (pharma residues, solvents, dye molecules, etc.). The idea is to
treat the wastewater on-site, at the source, before it even reaches
municipal treatment plants[16]. By
breaking down pollutants right where they are produced, the system prevents
them from ever entering the broader water system or public sewage. This point-of-source treatment** is a proactive model: industrial
facilities can ensure they aren’t discharging persistent pollutants, rather
than relying on downstream facilities to catch them. Early pilot results have
been very promising – the photocatalytic foam reactors have successfully
degraded target contaminants in real wastewater streams[17]. This
demonstrates that the technology works not just in clean lab water but also in
the complex soup of actual industrial effluents.
Encouraged by these results, the Fraunhofer teams are already working
on next-generation improvements. One area of ongoing research is
developing new catalyst formulations and optimizing the foam’s coating
techniques[18]. By
experimenting with different photocatalytic materials (for instance, doping
titanium dioxide with other elements, or using alternative semiconductors like
zinc oxide or graphitic carbon nitride), they aim to boost efficiency and
perhaps capture a broader spectrum of light (even visible light). They are also
exploring combinations of photocatalysis with adsorption – for example,
integrating activated carbon or zeolites into the foam to first soak up
ultra-dilute pollutants and then destroy them photocatalytically[18]. This
two-stage approach could tackle even trace pollutants that are otherwise below
the detection or action threshold of direct photocatalysis.
Looking ahead, the goal is to scale up the technology and
establish it as a key component of modern industrial water cycles[19]. In the
future, one could envision many factories and plants adopting these foam-based
photocatalytic reactors as a standard part of their wastewater management. The
modular nature means systems can be sized according to need, or multiple units
can operate in parallel. If widely implemented, such technology would
significantly reduce the load of micropollutants entering the environment.
Essentially, it would close the loop, enabling industries to handle their water
pollution on-site and even potentially reuse the treated water in a
circular manner.
In summary, light-activated foam ceramic reactors represent a
groundbreaking development in water treatment technology. By marrying advanced
materials (functionalized ceramic foams) with cutting-edge light sources
(UV-LEDs) and a green chemical process (photocatalytic AOP), the Fraunhofer
IKTS team has created a compact, energy-efficient system for destroying
pollutants that were previously deemed “treatment-resistant.” This innovation
not only addresses current environmental protection challenges but also paves
the way for more sustainable water use in industry. It’s a shining example of
how scientific ingenuity can illuminate a path toward cleaner water,
ensuring that even as industries grow, they can do so without poisoning our
precious water resources[20].
Sources: The information and quotes in this
article are based on the Fraunhofer IKTS press release “Cleaning water with
light – a new generation of compact and efficient water treatment systems”[6][17] and
related research news detailing the development of photocatalytic ceramic foam
systems for wastewater purification[5][21]. These
sources provide insight into the technology’s mechanism, pilot applications,
and potential impact on sustainable industrial water management.
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] 1.10.2025 Press release: Cleaning
water with light – a new generation of compact and efficient water treatment
systems - Fraunhofer IKTS
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