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The aim of this project was to develop photocatalytically active fiber materials for innovative environmental applications, with the degradation of pollutants in wastewater from textile dye processes
The issue of treating dyeing wastewater is highlighted by the alarming fact that approximately 10,000 different dyes and pigments are produced globally, with 20% ending up in the wastewater of dyeing facilities. Due to their potential toxicity to humans and the environment, coupled with their diverse chemical structures and high dilution in wastewater, efficiently and cost-effectively removing these dyes poses a significant challenge.
Due to the high stability of synthetic dyes and the elevated salt content in wastewater, biological degradation methods have limited effectiveness. Additionally, it is important to note that the biological degradation of azo dyes under anaerobic conditions can result in the formation of toxic aromatic amines, which further increase health risks. Alternative separation techniques, such as adsorption, membrane filtration, and coagulation, do not destroy the dyes but merely shift the disposal problem to expensive downstream processes.
In contrast, oxidation processes mineralize dyes, breaking them down into harmless CO₂ and water. These methods therefore represent a promising supplement to and combination with biological treatments. However, conventional oxidative water treatment methods (Advanced Oxidation Processes, or AOPs) such as chlorination, ozonation, and UV irradiation combined with hydrogen peroxide are costly and energy-intensive. This underscores the need for developing heterogeneous photocatalytic processes capable of fully degrading organic pollutants using light (ideally sunlight, for cost efficiency) and atmospheric oxygen.
Among the various oxide-based photocatalysts, titanium dioxide (TiO₂) is preferred due to its low cost, low toxicity, and strong oxidative properties. The photocatalytic activity of TiO₂ is primarily associated with its crystalline anatase modification, which is typically formed through thermal treatment.
The fabrication of TiO₂ coatings on thermally stable substrates is commonly performed via the hydrolysis of titanium alkoxides or halides to produce nanosols. This process initially forms amorphous TiO₂ particles, which, after coating and thermal annealing at temperatures exceeding 400°C, transform into crystalline TiO₂ coatings. This process initially forms amorphous TiO₂ particles, which, after coating and thermal annealing at temperatures exceeding 400°C, transform into crystalline TiO₂ coatings.
Since temperatures above 400°C are not feasible for conventional textile substrates due to their thermal decomposition, alternative synthesis methods had to be developed to produce coating solutions with a high crystalline anatase content, enabling moderate annealing temperatures below 200°C while preserving high photoactivity.
Challenges faced during the project:
By pre-coating or adding epoxy-silicon copolymers, the adhesion and wash stability of TiO₂ coatings on textile surfaces were achieved. The photocatalyst’s sensitivity in the visible light spectrum was improved through doping with silver, palladium, or tungsten compounds. This approach enabled the use of a broad light spectrum for the photocatalytic activation of TiO₂ in dye degradation.
ANSPRECHPARTNER:
Dr. Helfried Haufe
Fachsektion Dresden – “Funktionelle Schichten”
Tel.: 0351 / 2695 344
E-Mail: dresden@gmbu.de
© Gesellschaft zur Förderung von Medizin-, Bio- und Umwelttechnologien e.V.
