Anthropocene Magazine · Space

Ultra-Black Wool Converts Saltwater to Drinking Water Using Sunlight

Scientists developed an ultra-black wool material that purifies saltwater into drinking water using solar energy. This biodegradable material offers a low-cost alternative to conventional desalination.

The dyed wool reflects less than 0.5% of light and evaporates saltwater. The water meets WHO and EPA standards. This addresses water scarcity, projected to affect nearly half of urban populations by 2050.

Traditional desalination is energy-intensive. Existing solar methods often use expensive nanomaterials that risk leaching into water.

Researchers dyed merino wool with polydopamine and etched it to create microscopic spikes, mimicking riflebird feathers. This created the "darkest fabric ever made" that traps light.

The material acts as a solar water evaporator. Polydopamine converts near-infrared light to heat, while spikes trap light. A two-sided vertical configuration produced 2.43 liters/sq meter/hour.

This is simpler and cost-effective. A 20x20 cm piece costs ~$0.62. Modeling suggests a square meter could yield ~4,700 liters annually in sunny locations.

This could provide off-grid water for vulnerable communities. The material performed well on water three times saltier than seawater and will be tested on brackish water.

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