Cornell University researchers have demonstrated that specially dyed wool could provide a low-cost, renewable method for purifying salt water using sunlight. The approach combines natural fibers with interfacial solar vapor generation, or ISVG, a technique that concentrates heat at the water’s surface to accelerate evaporation and desalination, tells Cornell Chronicle.
The research addresses growing concerns about freshwater availability. Scientists project that nearly half of the world’s urban population could face insufficient potable water by 2050. The Cornell team, led by Larissa Shepherd, explored wool because it is biodegradable and avoids the potential microplastic waste associated with synthetic materials.
Researchers treated wool with polydopamine, or PDA, a melanin-inspired polymer that strongly absorbs near-infrared light and converts it into heat. They also tested an ultrablack version created through plasma etching, which produces nanoscale fibers that trap additional light. The ultrablack material was originally inspired by the exceptionally dark plumage of the magnificent riflebird, a bird of paradise.
The team tested three wool architectures in horizontal, one-sided vertical, and two-sided vertical configurations. In the two-sided arrangement, mirrors illuminated both sides of the textile. Ultrablack wool produced 2.43 kilograms of water per square meter of fabric per hour, while PDA-only wool achieved 2.21 kilograms. Both rates were nearly double those of conventional horizontal evaporation systems.
The system also operated continuously for 10 hours without salt buildup, an important requirement for practical desalination. Salt concentrations in the collected water remained well below World Health Organization drinking-water standards.
Interestingly, the researchers found that PDA-treated wool alone performed nearly as well as the more complicated ultrablack material, potentially simplifying production. Future research will examine its effectiveness with rainwater and wastewater while improving water-collection designs. The work suggests that an abundant natural textile could become part of accessible solar-powered water purification systems, particularly in areas with limited infrastructure.
