An inexpensive process that uses natural fibers embedded with nanoparticles almost completely rids water of toxic textile dyes in minutes, researchers report.
Dyes, such as indigo blue used to color blue jeans, threaten waterways near textile plants in South America, India, and China. The harmful dyes discolor the water, reducing light to plants, which limits photosynthesis and lowers the oxygen in the water.
The study, published in the journal Green Chemistry, describes a proof of principle, but researchers are testing how effectively the method treats such endocrine-disrupting water pollutants as phenols, pesticides, antibiotics, hormones, and phthalates.
“These molecules are contaminants that are very resilient to traditional water-purification processes, and we believe our biocomposite materials can be an option for their removal from waste water,” says study co-author Marianny Combariza, a researcher at Colombia’s Universidad Industrial de Santander.
The technology takes advantage of nano-sized cavities found in cellulose that co-author Juan Hinestroza, associate professor of fiber science at Cornell University, has previously used to produce nanoparticles inside cotton fibers.
The paper reports how Colombian fique plant fibers, commonly used to make coffee bags, are immersed in a solution of sodium permanganate and then treated with ultrasound.
As a result, manganese oxide molecules grow in the tiny cellulose cavities. Manganese oxides in the fibers react with the dyes and break them down into non-colored forms.
The treated fibers removed 99 percent of the dye from water within minutes. Furthermore, the same fibers can be used repeatedly—after eight cycles, the fibers still removed between 97 percent and 99 percent of the dye.
“No expensive or particular starting materials are needed to synthesize the biocomposite,” Combariza says. “The synthesis can be performed in a basic chemistry lab.”
“This is the first evidence of the effectiveness of this simple technique,” says Hinestroza. “It uses water-based chemistry, and it is easily transferable to real-world situations.”
The researchers are testing their process on other types of pollutants, other fibers and composite materials.
“We are working now on developing a low-cost filtering unit prototype to treat polluted waters,” says Combariza. “We are not only focused on manganese oxides, we also work on a variety of materials based on transition metal oxides that show exceptional degradation activity.”
Source: Cornell University