For hundreds of millions of years, trees have mastered the efficient movement of water upward against gravity. A recent study from researchers shows that they have set up Tree-based water transport system that uses capillary forces to pull out dirty water upward through a pyramidal structure aerogel and thus converting into steam by solar energy to produce fresh, clean water.
The researchers, directed by Aiping Liu at Zhejiang Sci-Tech University and Hao Bai at Zhejiang University, have published a paper on the new water transport and solar steam generation method in the journal ACS Nano. Efficient water transport methods could be used in water purification and desalination in near future.
Liu said that their production method is global and can be industrialized. Their resources have the best qualities, stability and can be recycled. This establishes the opportunity for extensive desalination and sewage treatment in near future.
The mechanism includes two major components. A long, porous, lightweight aerogel for transporting water and a carbon nanotube layer to absorb sunlight and convert water into steam covered in a glass vessel. Capillary forces generated by adhesion between the water molecules and the interior wall of the pores causes water to rise upward in the aerogel. Solar-heated carbon nanotube layer turns the water at the top into steam releasing impurities back. The water droplets formed by condensed steam on the walls of container flow down into a storage for collection.
Like carbon solar steam generator, plants pull water from the ground across branches and leaves by the help of tiny xylem vessels. Solar radiation causes leaves water to evaporate through tiny pores.
Compared to previous trials of tree-like water transport system showing suboptimal performance, reduced transport speeds and lesser transport distances, the new aerogel design showed optimisation in these fields obtaining upward flow performance of 10 cm and 25 cm in first 5 minutes and 3 hours respectively attaining a high energy conversion efficiency of up to 85%.
To enhance the set-up, researchers have build up the material by pouring aerogel ingredients into a copper tube keeping cold end at -90 degree Celsius causing ice crystal to grow. Tiny structures like pyramid with radially aligned channels, micro-sized pores, wrinkled inner surfaces, and molecular meshes obtained after freeze-drying the tube helped in aerogel best performance.
Liu said that they further want to enhance the speed and length of water transmission and efficiency of water storage to take forward practical implementation and achieve mass production.