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Photochemistry / Alfa Chemistry
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Water Disinfection


Photodynamic treatment with the help of photosensitizers is an alternative approach to wastewater disinfection. Natural photosensitizer, as a low-cost and pollution-free compound, can transfer light energy to oxygen under the excitation of visible light or ultraviolet light to produce highly active singlet oxygen, thereby killing bacteria, yeast, viruses, parasites and other pathogenic microorganisms.

Water DisinfectionFigure 1. The treated and disinfected wastewater.

Mechanism of Water Disinfection

Wastewater mainly comes from pharmaceutical, chemical, printing and dyeing, oil field, and papermaking process wastewater, which contains a large number of inorganic ions and microorganisms. The disinfection mechanism is as follows.

  • Inorganic Ion

Industrial wastewater contains many heavy metal ions and inorganic anions, such as Hg2+,Cr6+,Pb2+, CN-, NO-. Here, take the CN- for example.[1] After the photosensitizer is excited by light, it transfers energy to oxygen atoms, and the excited oxygen atoms oxidize CN- to OCN-, and finally decompose into CO2, N2 and NO3-.

  • Microorganism

There are so many microorganisms in water, which will lead to water quality worse. The photosensitizers typically interact with triplet oxygen species to produce reactive oxygen species. Reactive oxygen species attack bacteria, disrupting their cell membrane structure and causing the bacteria to rupture until die.

What Can Alfa Chemistry Do?

Alfa Chemistry's technical R&D team has focused on the preparation and application of photosensitizers for many years, which has established long-term cooperative relationships with many well-known enterprises and research institutions. We have conducted research on various problems encountered by water disinfection, we can customize solutions to meet customer needs in order to help researchers solve the problems. If you want to know more about our products, please contact us.


  • Valkov A.; et al. Water disinfection by immobilized photosensitizers. Water, 2019, 11(1): 26-38.

Please kindly note that our products and services are for research use only.