Environment

Fishing for oil with a polymer sponge

A team from USTC have developed a new oil collection apparatus based on a combination of HPS with pipes and a self-priming pump.

Recently, porous hydrophobic/oleophilic materials (PHOMs) have been shown to be the most promising candidates for cleaning up oil spills. However, due to their limited absorption capacity, a large quantity of PHOMs would be consumed in oil spill remediation, causing high material and transport costs. In addition, the complicated and time-consuming process of oil recovery from these sorbents is also an obstacle to their practical application.

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Fig. 1. (a) Image of the as-synthesized HPS; inset: water contact-angle measurement of the HPS. (b, c) SEM images of the HPS with low and high magnification. (d) Oil transportation mechanisms with the HPS fully filled with oil. (e) Photographs of continuously collecting n-hexane in situ from a water surface by our proposed oil connecting apparatus. (f) Capillary pressure changes in the oil–air and oil–water interfaces of the HPS during the suction process.

To solve the above problems, a team led by Prof. Shu-Hong Yu at the Hefei National Laboratory for Physical Sciences at Micrscale (HFNL), Department of Chemistry, Univeristy of Science and Technology of China (USTC) has provided a new model oil collection apparatus based on a simple combination of hydrophobic polymer sponge (HPS, a typical PHOM) with pipes and a self-priming pump, which can continuously and selectively collect oil in situ from a water surface with high efficiency. The results were published in Angew. Chem. -Int. Ed. and the publication was selected as a Hot Paper.

Based on the high efficiency of their pilot model apparatus, one can imagine a ship pulling a floatable collection net made of pipes, HPSs and pumps to deal with the oil spill instead of carrying a large amount of sorption powder materials. The researchers realised that this material will be called upon to perform in harsh sea conditions such as high wind or large waves, and so also studied the oil collecting performance of the apparatus on a turbulent water surface. The shaking of the HPS on water surface did not affect the oil separation efficiency due to its self-floating ability. In fact, as a result the oil on a turbulent water surface was more quickly collected into a beaker without taking in water.

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Fig. 2. Schematic illustration of the oil collection apparatus applied for future oil spillage and organic solvent leakage remediation: A ship pulling a floatable collection net made of pipes, HPSs and pumps to deal with the oil spill instead of carrying a large amount of sorption powder material.

The key to this design is the capillary pressures at oil-air and oil-water interfaces of HPS spontaneously regulate with the suction power applied to HPS and the unique interconnected macropores of the HPS, which ensures enough passage of oil inside the sponge.

The oil-air and oil-water interfaces prevents the permeation of air and water to HPS  – only floating oil is absorbed by the HPS and flows along the pipes to the collecting tank, leaving the HPS consistently able to uptake the oil present. This oil collection design saves sorbents, labor, and operation time, and as a result largely decreases the cost of oil collection. In the future, for large-area oil spills, oil-collecting ships could “fish” the floating oil by pulling a large floatable oil collection net made of pips, hydrophobic polymer sponges, and pumps. This foldable oil-collection net with unlimited oil-sorption capacity, small in volume, and easy to carry, may also be used as emergency facilities for tankers and drilling platforms in case of oil leakage.

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