Page 431 - AWSAR 2.0

limiting their use in practical settings.’ Awestruck, she further questioned, ‘How do you plan to design your research proposal around this area?’ With beaming confidence and pride, I declared, ‘I
aim to develop a durable, recyclable and bio-degradable superhydrophobic absorbent for oil/water separation.’
‘An ideal oil absorbent
should have (a) high porosity,
(b) high oil absorption capacity
and selectivity and (c) low
cost and also be environment
friendly,’ Dr Manna explained to
me. Over the next few days, I fiddled around with all the possibilities only to stumble upon mymother’smagiccottonball,ahighlyporous abundantly available fibrous substrate. The inherently hydrophilic smooth cotton fibres need to be coated with rough features to display superhydrophobicity. Therefore, after a detailed survey, I concluded to decorate the fibres with nanometre-sized particles derived from the commercially available, abundant and cheap bovine serum albumin (BSA) protein found in cows. These protein nanoparticles were stabilized on the substrate following a rapid and facile covalent chemistry and, further, the extreme water repellent property was modulated with the aid of a hydrophobic molecule. Therefore, BSA nanoparticle-coated superhydrophobic cotton was successfully fabricated for the very first time. The next few days were spent tirelessly testing the fabricated material for its physical and chemical durability. On bending, creasing, twisting and winding the superhydrophobic cotton, it was observed that the embedded extreme water repellent property remained intact. On exposure to even harsher physical abrasive tests, including adhesive tape test (the cotton is peeled using adhesive tape), sandpaper abrasion
Ms. Arpita Shome || 407
(sandpaper is rubbed back and forth on the cotton), prolonged ultraviolet irradiation and exposure to chemically harsh aqueous media (for 30 days), that is acidic, basic, surfactant
contaminated, river water and seawater, it was interesting to note that the water droplet continued to roll off the surface of cotton without pinning. Elated with these results, my supervisor encouraged me to further test the material for its applicability in oil/water separation. On exposing the superhydrophobic cotton to a floating oil (crude oil)/water
interface, it selectively absorbed only the oil phase while repelling the water phase, and the absorbed oil could be re-collected by squeezing the material without any traces of water. Such a material could also be extended for the collection of heavy oil sediment at the bottom of the water. The oil absorption capacity per gram of the material was found to be more than 2000 wt% for oils with varying viscosities.
Fig. 1. (A) Water droplets on a lotus leaf. (B) Protein nanoparticle–derived superhydrophobic cotton. C-E) Absorption of light oil (crude oil) from oil/water interface and re-collection of oil (E). (F–H) Separation of sediment oil from water and re- collection of oil (H).
‘An ideal oil absorbent should have (a) high porosity, (b) high oil absorption capacity and selectivity and (c) low cost and also be environment friendly,’