A comparative study on superhydrophobic sponges and their application as fluid channel for continuous separation of oils and organic solvents from water

This study adopted melamine as core material to prepare porous materials possessing superhydrophobic and superoleophilic property, which is utilized to separate polar and non-polar solvents from polar/non-polar mixture. The sponges were treated by four different methods; (1) acetone treatment, (2) coating of functionalized expanded graphite (FEG), (3) coating of multi-walled carbon nanotubes (MWCNTs) and, (4) coating of reduced graphene oxide (rGO). After treatment, the functional groups on the sponge skeleton were examined and the water contact angles were also measured. Based on the experimental results, sponge treated with acetone showed the best absorption capacity, but worst hydrophobic property; while the sponges coated with FEG and MWCNTs possessed the worst absorption capacity. The sponge coated with reduced graphene oxide showed notable superhydrophobic property, as well as excellent absorption capacity. In this work, we also designed a set-up to separate organic solvents from organic-water mixture using the superhydrophobic and superoleophilic sponge. The basic idea is that, when the mixture of solvent and water was poured in the upstream of the channel, the solvent was absorbed by the treated sponge which was placed at the bottom of the channel, while water flowed down along the channel; as a result, separating the solvent from the mixture.