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SPECIALIZED TEXTILE MATERIALS FOR SEFLCLEANING (Photo-catalytic textiles)


Type of program and project: Capacities, Modul III, bilateral project (Romania-Turkey)

Contract number: 381/26.04.2010

Finalization year: 2011

Project duration: 1 year and 7 months

Romanian Partner: National Research and Development Institute for Textiles and Leather

Turkish partner: Ege University, Textile Engineering Department

Financing Authority:
for Romanian side - National Research Authority (ANCS)
for Turkish side - The Scientific and Technological Research Council Of Turkey (TUBITAK)

Objectives:

The main objective was the manufacturing of photocatalytic textile materials.

In order to achieve the proposed objective, the following specific objectives were defined:
1) Experiments and synthesis of TiO2 based photocatalytic compunds;
2) Development of application technologies of photocatalytic compounds on textile materials;
3) Characterization of products efficiency through physical, chemical, microbiological tests.

Results and short description

1. Study regarding the photodiscolouring efficiency of methyl orange dye induced by TiO2/Ag based photocatalysts
- In the absence of photocatalysts, after 585 minutes, only 52,5 from UV exposed methyl orange is degraded;
- Photodegradation of methyl orange increases with increasing irradiation time, regardless of the concentration of silver in photocatalyst;
- The efficiency of photodegradation increases proportionally with increasing concentration of photocatalyst. At high concentrations of photocatalyst, photodegradation efficiency decreases due to agglomeration of nanoparticles and of reducing of surface exposed to light;
- Sedimentation of nanoparticles and the absence of oxygen leads to the reduction of photocatalytic activity;
- Covering of TiO2 particles surface with a high number of negatively charged Ag particles, contributes to reduction o photocatalytic efficiency;
- Most intense photodegradation is found in photocatalyst with a content of silver ions of 0,00012% Ag.

2. Study regarding of methyl orange photodegradation kinectics in the presence of photocatalytic compounds
Discoloration of the methyl orange (MO) in aqueous solutions of TiO2¬ can be described using first order kinetic model, ln (A0 / A) = kt, where A0 is the initial absorbance and A is the absorbance at any time, t.
Photodegradation follows a three stages model: initial-slow (due to high concentrations of methyl orange that prevent light from entering photocatalyst layer), followed by a rapid phase (due to the number of reactive species formed), followed by phase III, which takes place at a very low speed due to photocatalyst deactivation by gradually blocking of active centers by reaction products formed at the surface of the catalyst.
Another explanation for the slow reaction kinetics after a certain time of photodegradation, could be the competition between dye photodegradation and of intermediate compounds formed in the photodegradation process. The presence of to much silver decreases photocatalytic activity of TiO2 due to barrier effect, blocking both diffusion and light penetration to the surface of titanium oxide.

3. Study regarding the methyl orange photodegradation by FT-IR spectrometry
Compunds resulting from the photodegradation process of methyl orange by Ag/TiO2 based photocatalysts were determined by FT-IR spectrometry, on 400-4000 cm-1 domain, in alcoholic solutions, on KBr pills and crystals of CaF2.
After an hour of exposure to UV radiation, it can be observed the preservation of azoic structure of methyl orange, indicated by the presence of benzene rings characteristic frequencies (1411, 860cm-1), characteristic bond of –N=N- group, located at 1657cm-1 and the sulpho group, SO3 - located at 1042cm-1.
After 3 hours of exposure to UV radiation, bands specific to methyl orange disappear, and bands specific to photodegradation products appear, like p- dimethylaniline.
After 4 hours of exposure to UV radiation, it can be observed the disappearance of organic compunds characteristic bands and the presence of bands specific to used photocatalysts, respectively Ag/TiO2 nanoparticles.

4. Study regarding the methyl orange photodegradation by Ag/TiO2 photocatalytic compounds by thin layer chromatography
It was performed by diazotation and coupling of degradation compounds with β-naphthol. Detected spots, with different colors and different migration distances are assigned to amines resulted in the photodegradation of methyl orange, p-dimethylaniline, and sulphanilic acid.

5. Study regarding the methyl orange photodegradation in the presence of photocatalytic compounds by liquid column chromatography
Peaks were found, belonging to photodegradation products that after 120 minutes disappear as a result of mineralization of all products existing in solution.
6. Study regarding the morphological structure of treated materials
SEM images reveal deposition of TiO2/Ag particles on textile materials. Load degree is 0,94% for compound containing 75ppm Ag, 1,05% - 750ppm Ag and 0,68% - 1500ppm Ag.
Correlating photocatalytic effect with mass increasing, we can say that the photocatalyst containing 750ppm Ag is the most efficient in terms of photodegradation of organic compounds.

7. Study regarding the photocatalytic effect of textile materials treated with TiO2/Ag based compounds
photocatalytic efficiency of the fabrics treated with TiO2/Ag was tested by decomposing methyl orange in solar light and artificial light (standard - SR EN ISO 105-B06:4; Xenon lamp, 1000 W; 100 hours of exposure). Treated materials, exposed to artificial light, discolor faster than the untreated control, the most intense color fading being observed at the material treated with solution containing 750ppm

8. Material treatment methods with photocatalysts solutions and waterproofing agents
To increase the photocatalytic efficiency, the textile materials were treated with a waterproofing agent, NUVA TCC, in three versions: fulardation with photocatalyst-drying-fulardation with NUVA TCC-condensation; fulardation with NUVA TCC-drying-condensation-fulardation with photocatalyst-drying; fulardation with photocatalyst together with NUVA TCC-drying-condensation.

9. Study regarding the physical-mechanical characteristics of the abrics treated with photocatalysts and waterproofing agent
Treated materials were characterized physical-mechanical (mass, thickness, density, permeability air / water, breaking strength, thermal resistance and thermal conductivity).
No change was observed as the photocatalysts don’t essentially modify physical-mechanical properties. All materials show a high resistance to wetting. Method 3 allows the deposition of a higher amount of polymer (and/or nanoparticles) on the surface of the material. SEM images demonstrate the deposition of the polymer and particles on the material.

10. Study regarding the microbiological behavior of the fabrics treated with TiO2/Ag based photocatalysts
Textile materials treated with Ag/TiO2 photocatalysts inhibit 100% of Candida albicans colonies growth.

Future collaboration:
This project represent a diversification and development of the research themes realized together with the Turkish team from the Textile Engineering Department, initiated between INCDTP and Ege University in the frame of the Bilateral Projects Programme financed by ANCS and TUBITAK and it generates new opportunities for the development of research themes of actual interest, which can be unreeled through national and international projects.
Also the project is in the spirit of the INCDTP research strategy to develop new materials and textile technologies.

Contact:
- General Manager, Dr.eng. Pyerina Carmen Ghituleasa, certex@ns.certex.ro
- Project Director, biol. Clara Radulescu, clara.radulescu@certex.ro
- Principal investigator, Dr.eng. Iuliana Dumitrescu, iuliana.dumitrescu@certex.ro
-Project Director from the Turkiesh side: Aysegul Korlu, aysegul.ekmekci@ege.edu.tr