Chemical Engineering Science, Vol.207, 970-979, 2019
Selective adsorption of oil on self-organized surface patterns formed over soft thin PDMS films
A new, simple, cost effective and facile method of adsorption of oil from oil - water mixture on self-organized patterns formed over a soft thin elastic film has been developed, which is of great ecological importance. Surface corrugations (such as columns, labyrinths and cavities evolved spontaneously due to instability on the surfaces of a thin soft elastic PDMS film in adhesive contact with a contactor) along with the oleophilic nature of the film help in selective adsorption of the oil from the oil-water mixture into the intervening surface spaces. The increase in RMS surface roughness brought about either by increase in adsorbent weight or by formation of a columnar structure (instead of cavities or labyrinths) was found to have a significant incremental effect on the true surface area creation by formation of increased number of oil adsorption sites: leading to higher oil penetration and thus, higher oil adsorption. For 0.3 wt% of adsorbent, adsorption was found to be maximum for columnar structures at 23%, followed by cavities at 15% and minimum with labyrinth at around 12%. The ratio (d(p)/d(d)) of the substrate pore size dimension (d(p)) to the surface oil droplet dimension (d(d)) in crude oil, motor oil, diesel and petrol were found to be progressively lower and hence the maximum adsorption and penetration in the columnar patterns was recognized in case of crude oil. The different oil morphology on adsorption can be greatly used as a marker to identify different category of oil. The surface columns fabricated by self-organization was found to adsorb double the weight of the adsorbent, and moreover the quantity of the polymeric material required in the present case was much less than that for bulk adsorbents, and also does not involve any additional functionalization or use of any external template material, making this method a very suitable one for selective oil adsorption. (C) 2019 Elsevier Ltd. All rights reserved.