TEXTILES.ORG
A research team at the Vienna University of Technology (TU Wien) in Austria is exploring the use of filters made from cellulosic waste to remove potentially harmful dyes from textile wastewater. According to a report in Ecotextile News, the researchers have used waste materials, such as old cleaning cloths and paper cups, which are then used to coat a fine nanofabric to create an efficient filter for polluted water.
The team found that azo dyes, which are widely used in the textile industry, often end up in wastewater and even when various filtration materials are used, the cleaning effect is often unsatisfactory.
Günther Rupprechter from the Institute of Materials Chemistry at TU Wien explained, “It’s much better to create a nanofabric out of lots of tiny fibers and let the water seep through. The water then comes into contact with a much larger surface area, and thus many more organic dye molecules can be bound.”
The team worked with semi-crystalline nanocellulose, which can be produced from the cellulose-based waste material. This nanocellulose is then “spun” together with an acrylic-like polymer, such as polyacrylonitrile, into the nano-structures. The electrospinning process was especially important, during which the material was sprayed in liquid form with the droplets then electrically charged and sent through an electric field.
“This ensures that the liquid forms extremely fine threads with a diameter of 180 to 200 nanometers during curing,” Rupprechter says, noting that the threads then form a fine tissue with a high surface area called a nanoweb. A network of threads measuring one square centimeter then equates to a total surface area of more than 10 square centimeters, he says.
Results show that over three cycles, water contaminated with a violet dye was purified, and 95 percent of the dye was removed. “The dyes remain stored in the nanoweb. You can then either dispose of the entire web, or regenerate it, dissolve the stored dyes and reuse the filter fabric,” he said.
The next stage in the project will see the team evaluating the mechanical properties of the sophisticated nanowebs, conducting biocompatibility tests, assessing sensitivity to more complex pollutants, and achieving scalability to industrial-grade standards.
There will also investigate how this dye filter technology can be transferred to other areas of application. “This technology could also be very interesting for the medical field,” Rupprechter adds. “Dialysis, for example, also needs filtering out very specific chemical substances from a liquid. Coated nanofabrics may be useful for such applications.”