Method successful at removing dyes, separating fabric blends

It is becoming harder and harder to ignore the environmental costs of textiles, and demand is still growing by leaps and bounds each year. 

Textile recycling has vexed researchers and the industry, but it is a problem that must be solved, said University of Nebraska–Lincoln researcher Yiqi Yang. He has developed a first-of-its-kind technology for fiber-to-fiber, or chemical, recycling that successfully removes dyes, separates natural and synthetic blends and creates high-quality fibers.

“In the last 20 years, the total fiber production has doubled,” said Yang, Charles Bessey Professor in Textiles, Merchandising and Fashion Design and Biological Systems Engineering. “Right now, we consume more than 125 million metric tons of fibers per year. We cannot grow more natural fibers or raise more sheep. That’s not realistic, so we’re using more synthetic fibers, but the issue there is the ramification of nondegradable microparticles. 

“If you can reuse fibers once or twice, that will be a huge reduction on the demand for new fibers and textile materials.” 

Textile recycling exists, but it is limited mostly to breaking down textiles into fibers for uses in other products. Garment-to-garment recycling, or upcycling, is very limited and cannot be done on an industrialized scale. Yarn-to-yarn, or mechanical, recycling is available, but the process is destructive and requires adding more than 50% of virgin fibers to make usable yarns.

Fiber-to-fiber recycling has been difficult to achieve, if not impossible, because of dyes and textile blends. Yang and an interdisciplinary team, including doctoral student Yuanyi Shao, developed an aqueous system technology that produces high-quality fibers. 

“Dyes are designed to have strong affinity to fibers for excellent colorfastness, so it is difficult to remove the dyes, and what we have done, first in the world, is to find a way to remove the dyes, without damaging the dyes or the fiber polymers,” Yang said. “It not only recycles the fibers successfully, but also recycles the solvents and dyes used in the process.” 

Yang is pursuing a patent for the technology and has published a series of articles demonstrating the successful application of the technology on many fibers, from cotton and cotton-polyester blends to acrylics and wools — even carpet. Yang’s latest paper, published in Resources, Conservation and Recycling, applies the technology to used denim and shows that the system can successfully remove vat dyes from textiles, and to produce artificial cellulosic fibers with properties better than that from the artificial fibers using wood pulp. The research has also shown that the process is economically viable and scalable.

“Using our technology, you can recycle fibers from any textiles cost effectively, with excellent properties,” Yang said. “Everything we did was having large-scale production in mind. Of course, we have to have industry interest because the industrial application requires heavy capital investment.”

Yang’s research team aims to minimize the environmental costs and increase the sustainability of the textile industry, with attention paid to two avenues: improving recycling, and creating new textiles from agricultural waste, such as chicken feathers. 

“I just don’t see the future without these two choices that we are working on,” Yang said. “We need to find new solutions to make more fibers and then recycle what we have. Without the two, we cannot meet the demands.”