Water pollution with crude or mineral oil has become an ongoing problem in our society. Methods used to clean up oil spills have problems of their own. Chemical substances used to decompose the oil faster, and burning the oil, both cause secondary pollution. Accidents on oil drilling and production platforms, oil tanker disasters and damaged pipelines all contribute to the ever growing problem. Although a number of natural materials such as plant fibers and sawdust have been experimented with to take up the oil, these are not effective as they also absorb large amounts of water.
The head of the Biomimetic Surfaces Group of the Institute of Microstructure Technology of KIT, Hendrik Hölscher says they are continuously studying microstructures and nanostructures in nature to find potential technical solutions. In one such search led by Claudia Zeiger, scientists compared various species of aquatic ferns with the specific aim of finding environmentally friendly alternatives that can be used to clean up oil spills. While it has been known for a while that the leaves of these ferns repel water, the study focused on their capacity to absorb oil.
Zeiger’s team from KIT, working with colleagues of Bonn University, have determined that the oil-binding capacity of the water ferns is achieved by the hairy microstructure of its leaves. This newfound knowledge is now used to enhance the Nanofur material originally developed at KIT. Nanofur can be used for the cleanup of oil spills in an environmentally friendly way.
Aquatic ferns are often considered weeds due to their strong reproduction. They can be found in parts of Europe although they originated in tropical and subtropical regions. Zeiger feels they have huge potential to be used as rapid, low cost and environmentally friendly oil absorbers.
A specific water plant named salvinia has the most potential as they have hairy extensions of 0.3 to 2.5 mm in length on their leaves. These are called trichomes. Contrary to what one would think, the oil absorbing capacity of different species is not determined by the length of the trichomes, but rather by the shape. In tests done on lakes where accidental oil spills occurred, leaves of the salvinia absorbed oil to their maximum capacity in under 30 seconds. The leaves together with the absorbed oil, is then simply skimmed off the surface of the water. The species salvinia molesta was found to be the most effective in oil absorption. Its hair ends are shaped like an eggbeater. The improved plastic Nanofur copycats both the oil absorbing and water repellent properties of salvinia to separate oil and water.
Research has been published in the journal Bioinspiration & Biomimetics.