A group of scientists at Abu Dhabi’s Khalifa University has discovered a method to extract toxic dyes from wastewater being dumped into waterways without the benefit of pre-treatment.
The marine life-based method uses mussel-inspired polydopamine (PDA) as an adsorbent to remove anionic (acid) dyes from water, using Alizarin Red S as a model pollutant. PDA has a high binding ability, even to different or very wet surfaces. This extraordinary self-adhesive property of the PDA, combined with biocompatibility, give it broad possibilities for removing the toxins. In addition, it showed fast absorption kinetics, excellent selectivity toward the acid dyes and high regeneration efficiency.
The colorless and therefore dye-free liquid was achieved by shaking it for 24 hours at 150 RPMs, at a temperature of 77 degrees Fahrenheit. The problem, according to Harrie Schoots, a textile chemist and consultant who’s worked with Microban and Ascend, is leaving a substance in a liquid carrying anionic dye which might result in harm to aquatic life and humans. He said, too, that the color should disappear on contact with the liquid and not require a full day of motion to see it removed.
“You don’t know if a reduced dye is truly non-reactive or safe,” he said. “It’s better to capture the substance and remove [it] physically from the water.”
“These are things we should all be paying attention to,” said Schoots, who is a former president of the American Association of Textile Chemists and Colorists.
He added that this technology could be relevant to the nylon 6.6 and wool supply chains both using these dyes, which is typically used in clothing and uniforms manufactured for the U.S. military and activewear brands like Lululemon.