Bioinspired oil-water separation approaches for oil spill clean-up and water purification

Water contamination is one of the major environmental and natural resource concerns in the twenty-first century. Oil contamination can occur during operation of machinery, oil exploration and transportation, and due to operating environment. Oil spills occasionally occur during oil exploration and transportation. Water contamination with various chemicals is a major concern with growing population and unsafe industrial practices of waste disposal. Commonly used oil-water separation techniques are either time consuming, energy intensive and/or environmentally unfriendly. Bioinspired superhydrophobic/superoleophobic and superoleophobic/superhydrophilic surfaces have been developed which are sustainable and environmentally friendly. Bioinspired oil-water separation techniques can be used to remove oil contaminants from both immiscible oil-water mixtures and oil-water emulsions. Coated porous surfaces with an affinity to water and repellency to oil and vice versa are commonly used. The former combination of affinity to water and repellency to oil is preferred to avoid oil contamination of the porous substrate. Oil-water emulsions require porous materials with a fine pore size. Recommended porous materials include steel mesh and cotton fabric for immiscible oil-water mixtures and cotton for oil-water emulsions. A review of various approaches is presented in this paper. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 2)'.