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Project ID: ICA3-CT-2002-10016
Financiado con arreglo a: FP5-INCO 2
País: Spain

Polymeric support to water disinfection by singlet oxygen generation

Our research group has developed a singlet oxygen photosensitizing material made of porous silicone and an adsorbed polyazaheterocyclic Ru(II) coordination compound [tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II)].

Singlet oxygen is the lowest excited state of molecular oxygen. As a reactive oxygen species it has an electrophilic character, an energy excess of ca. 95 kJ mol 1 over its ground state and a long lifetime in condensed phase. It is known to inactivate bacteria efficiently since it is able to react with the proteins and lipids present in biological membranes.

The key innovative features of this result are the following:
- Singlet oxygen is efficiently produced by the Ru(II) photosensitizer immobilized on the polymer support.
- The reactive oxygen species has a long lifetime, which is an essential feature in order to allow singlet oxygen diffusion from the silicone material towards the external aqueous phase.
- The use of porous silicone displays the following advantages: high oxygen permeability (high oxygen solubility and large oxygen diffusion coefficient), the porosity of the polymer allows easy interaction with microorganisms to promote disinfection, the polymer shows good mechanical, thermal and chemical stabilities, and good optical properties as well.
- The use of Ru(II) photosensitizers shows the following advantages: strong light absorption in the visible range (400-550 nm), long excited state lifetimes (in the microsecond range) to allow collisional deactivation by molecular oxygen, and high probability of excited state quenching by oxygen leading to singlet oxygen.

The photosensitizing material can be produced at large scale and tests that demonstrate the viability of this material for water disinfection with solar light have been performed with two solar photoreactors with different configurations. Efficient disinfection of gram and gram(+) bacteria has been achieved with solar collectors containing less than 1 m2 of polymer illuminated area, allowing a daily production of 20-40 L of disinfected potable water. On site tests in developing countries such as Morocco, Tunicia and Egypt are currently underway to demonstrate the applicability of this technology to water disinfection in rural communities. Dissemination of these results among public institutions will facilitate the use of this technology and will maximize the benefits in terms of public health and life quality of population in developing countries.

The photosensitizing material (1.5 m x 4 cm x 2 mm died porous silicone strips has been produced at large scale in order to provide our partners with enough stripes to carry out their water disinfection tests.
- The photosensitizing material can be easily installed in the coaxial or fin-type solar reactor prototypes for water disinfection developed in this project.
- The photosensitizing material is very stable when kept in the dark and can be stored for a long time.
- The photosensitizing material has an operational life of at least half a year on a daily use basis (about 1MJ/m2 day, in the 360-700 nm region).
- The photosensitizing material installed in the prototypes can disinfect at least 20 L of water per day with an accumulated radiation dose of 0.8 MJ/m2. (100 CFU/mL initial bacteria concentration of E Coli or E Faecalis).

Solar Photocatalytic Decontamination and Disinfection of Water using New Photoreactor (Compound Parabolic Collector. The photocatalytic treatment of water contaminated with E.Coli have been carried out. Tests have been done using: supported titanium dioxide (TiO2 PC500) on non-woven paper sheet; polymer supported Ru(II)-complexes.

We can conclude that the use of UV-VIS sunlight to disinfect contaminated drinking water in a full-scale continuous flow solar reactor is promising.

The main objectives of this study are:
- Assessment of the disinfection ability of Ru(II) [RuL3] coordination compounds
immobilized on polymer strips on E. Coli in two CPC collectors under natural solar irradiation.
- Comparison of main reaction parameters: initial concentration of E.Coli, performance of different catalysts, reactor configuration, flow rate.
- Study of the disinfection capability of Ru-photosensitizer and TiO2-photocatalyst
coupling system.

The bacterial strain used is E. Coli K-12.
Experimental series: initial conc. 1exp4 CFU/mL and > 1exp4 CFU/mL. 10L/min of flow rate. Results obtained for the supported photosensitizer material are compared with those obtained with other photocatalyst material KN47, developed by Ahlstrom (France).

The total irradiation time was 90 minutes.
Disinfection at E. Coli concentrations of Co -1exp4 CFU/mL
In the range of bacterial concentration under study the Ru(II) [RuL3] catalyst shows a
higher disinfection capability than the KN47 Ahlstrom paper.

Información relacionada

Reported by

UCM (Universidad Complutense de Madrid)
Department of Organic Chemistry, Faculty of Chemistry Av Complutense s/n
28040 MADRID
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