According to UNESCO, 26% of the world’s population lacked access to safe drinking water in 2023, and this problem may worsen in the future. The main water pollutants are E. coli, arsenic, pesticides, and household waste. Current purification methods include physical, chemical, and biological approaches, including photocatalytic purification.
The process works as follows: Water first enters a reactor with a photocatalyst, typically titanium dioxide (TiO₂). When exposed to ultraviolet light, TiO₂ nanoparticles exhibit photocatalytic activity in water decomposition reactions, producing highly reactive hydroxyl radicals that mineralize organic chemical compounds and deactivate biological pathogens. A significant drawback of titanium dioxide is its UV absorption range.
The reactor is equipped with an ultraviolet light source — most commonly mercury gas-discharge lamps that operate at up to 300 nanometers, have high power, and last long. However, they also have disadvantages — mercury is a chemically hazardous substance, posing risks of emissions and requiring additional disposal costs.
“The power of mercury lamps decreases significantly when the distance between the irradiated solution and the light source increases, so the concentration of ozone generated near the lamp during water disinfection can far exceed sanitary standards. We propose an alternative to mercury lamps — high-power UV-LEDs, which share the advantages of conventional LEDs: environmental friendliness, energy efficiency, long service life, and minimal power dissipation with distance,” said Ekaterina Moiseeva, a research intern at the Skoltech Photonics Center and the first author of the patent.
“The transition to low-cost, eco-friendly high-power LEDs can be achieved by creating a hybrid composite with a phthalocyanine dye. The working principle of titanium dioxide as a photocatalyst is based on its semiconductor properties: First, a photon is absorbed, generating free electrons and holes, then these particles actively react with oxygen and water on the semiconductor surface, producing hydroxyl radicals and other highly reactive oxygen-containing compounds. The key difference with the hybrid material is that the photon is absorbed by the phthalocyanine, and the resulting electron is transferred to titanium dioxide, after which the known mechanism is activated. The result is a wastewater treatment photocatalyst capable of functioning under visible light,” added Professor Dmitry Gorin from the Skoltech Photonics Center, co-author and scientific supervisor of the patent.
The photocatalyst is an inexpensive, readily available, and non-toxic substance that demonstrates high chemical and mechanical stability. It utilizes water and oxygen as reagents — both naturally available in the environment — eliminating costs associated with their procurement, transportation, and storage. As researchers note, the photocatalytic water purification technology is unique because it simultaneously removes organic compounds while performing disinfection. Unlike direct photolysis methods, it prevents the formation of intermediate photocyclization products. Instead, organic compounds undergo complete oxidation to carbon dioxide and water or become mineralized. The photocatalytic reactor can be employed either as a standalone unit or integrated into wastewater treatment systems alongside conventional purification technologies, including sand filters, carbon filters, and reverse osmosis systems.
The development of the photocatalyst was carried out in collaboration with the Department of Medical Chemistry at Lomonosov Moscow State University’s Faculty of Chemistry.
