Efficiently Separating Oil & Water

A superhydrophobic coating turns fabric, mesh and sponges into functional oil and water separating materials.

AsianScientist (Jan. 9, 2015) – Scientists have developed a dip coating method for creating functional oil-water separating materials. Their research, published in the Journal of Colloid and Interface Science could help to produce materials used to separate oils from industrial waste waters, polluted oceanic waters and clean up oil spills.

Porous materials such as sponges, textiles and metal meshes are good candidates for oil–water separation due to their large pore volume, flexibility and commercial availability. However, these materials suffer from large coincident water absorption along with the oil.

To mitigate this problem, various research groups have tried to design functional materials with improved surface textures and novel chemistries. However, existing techniques are either laborious or substrate restricted, while others show disadvantages of low selectivity and limited recyclability.

The research group for composite lubricating materials at the Lanzhou Institute of Chemical Physics (LICP) of the Chinese Academy of Sciences has now developed the dip coating approach to produce three functionally porous materials used for oil–water separation. Fabric, copper mesh and sponge were endowed with superhydrophobicity (water-repelling ability) by modification with H-SiO2-PFW through a dip coating process.

The superhydrophobic fabric (A) and superhydrophobic copper mesh (C) used for oil–water separation. Hexadecane (colored with oil red) easily pass through the fabric and copper mesh, whereas water droplets (AgNO<sub><figcaption id=3 aqueous solution, dyed with methylene blue) bead up on their surfaces. Credit: Zhang Zhaozhu et al.” width=”650″ height=”180″ class=”size-full wp-image-53023″ /> The superhydrophobic fabric (A) and superhydrophobic copper mesh (C) used for oil–water separation. Hexadecane (colored with oil red) easily pass through the fabric and copper mesh, whereas water droplets (AgNO3 aqueous solution, dyed with methylene blue) bead up on their surfaces. Credit: Zhang Zhaozhu et al.

The functional materials described in the study can be used as a separation membrane or oil sorbent scaffolds. The researchers found that water droplets can roll off these material surfaces easily, while organic liquids such as hexadecane can wet them completely. These functional materials used for oil–water separation also possessed good reusability, evidenced by ten cycles of oil–water separation testing.

The article can be found at: Zhu et al. (2014) A Versatile Approach to Produce Superhydrophobic Materials Used for Oil–Water Separation.

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Source: Chinese Academy of Sciences.
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