Wastewater often contains a cocktail of organic pollutants, ranging from pesticides to pharmaceutical residues. These are difficult to remove using conventional purification methods.
However, a recent doctoral thesis from the Norwegian University of Science and Technology (NTNU) presents a creative method to get rid of them.
“We can break down the harmful chemicals in the water using sunlight and small droplets of oil,” said NTNU’s Zygimantas Gricius.
“Gricius and his colleagues have studied the purification of industrial wastewater. They looked at the breakdown of naphthenic acids, which can be found in wastewater from the petrochemical industry, chemical production and the textile industry,” said Gisle Øye, a professor at the Department of Chemical Engineering who was Gricius’ academic supervisor.
The small droplets of oil are called photocatalytic Pickering emulsions. An emulsion is a mixture of two liquids that are not completely soluble in each other. The droplets act as tiny chemical reactors that can break down organic pollution.
“The oil droplets are stabilized by nanoparticles that are activated by light, such as from the sun,” Gricius said.
One promising nanoparticle is titanium dioxide (TiO₂). The particles position themselves between the oil and the water where they capture sunlight and initiate reactions that break down the pollutants.
The research focused on fine-tuning these mixtures so that they became more effective, stable and reusable. Gricius identified several useful factors.
The thesis not only provides new insights into photocatalytic emulsions, it also demonstrates how we can think innovatively about sustainable water purification.
“By combining sunlight, smart materials and chemical additives, we have found an inexpensive, reusable and scalable method to purify contaminated water,” said Gricius.
The technology is still in an early stage, so the researchers haven't reached out to the industry yet. There are currently no commercial products based on Pickering emulsion technology. This is partly because the field of study has only recently experienced a renaissance and been recognized as industrially promising.
The project was a collaboration between the Ugelstad Laboratory, the Catalysis Group and the Particle Technology Centre at NTNU’s Department of Chemical Engineering.
Gricius worked with students Cippora Magagnin, Adriana Mina and Laurine Mroz. Magnus Rønning also contributed as project supervisor.
References:
Zygimantas Gricius, Cippora Magagnin, Adriana Mina, Gisle Øye, Design of TiO2-poloxamer stabilized Pickering emulsions for the photocatalytic degradation of 4-propylbenzoic acid , Chemical Engineering Journal Advances, Volume 22, 2025, 100730, ISSN 2666-8211 . https://doi.org/10.1016/j.ceja.2025.100730
Zygimantas Gricius, Gisle Øye. Pickering Emulsions Stabilized by Hybrid TiO2-pNIPAm Composites for the Photocatalytic Degradation of 4-Propylbenzoic Acid . ACS Omega 2025, 10, 2, 1988-2002, Published 7 January 2025. https://doi.org/10.1021/acsomega.4c07847
Zygimantas Gricius, Gisle Øye. Recent advances in the design and use of Pickering emulsions for wastewater treatment applications . Soft Matter. Issue 5, 2023.
Chemical Engineering Journal Advances
Experimental study
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Design of TiO2-poloxamer stabilized Pickering emulsions for the photocatalytic degradation of 4-propylbenzoic acid
19-Mar-2025