Novel fabrication of a robust superhydrophobic PU@ZnO@Fe3O4@SA sponge and its application in oil-water separations

Viet-Ha Thi Tran,Byeong-Kyu Lee

doi:10.1038/s41598-017-17761-9

Abstract

We report a novel superhydrophobic material based on commercially available polyurethane (PU) sponge with high porosity, low density and good elasticity. The fabrication of a superhydrophobic sponge capable of efficiently separating oil from water was achieved by imitating or mimicking nature’s designs. The original PU sponge was coated with zinc oxide (ZnO), stearic acid (SA) and iron oxide particles (Fe3O4) via a facile and environmentally friendly method. After each treatment, the properties of the modified sponge were characterized, and the changes in wettability were examined. Water contact angle (WCA) measurements confirmed the excellent superhydrophobicity of the material withhigh static WCA of 161° andlow dynamic WCA (sliding WCA of 7° and shedding WCA of 8°). The fabricated sponge showed high efficiency in separation (over 99%) of different oils from water. Additionally, the fabricated PU@ZnO@Fe3O4@SA sponge could be magnetically guided to quickly absorb oil floating on the water surface. Moreover, the fabricated sponge showed excellent stability and reusability in terms of superhydrophobicity and oil absorption capacity. The durable, magnetic and superhydrophobic properties of the fabricated sponge render it applicable to the cleanup of marine oil spills and other oil-water separation issues, with eco-friendly recovery of the oil by simple squeezing process.

Highlights

With the increasing use of fossil fuel and the global population growth, oil spill accidents occurring during oil utilization and transport processes have adversely impacted the environment
After a facile zinc oxide (ZnO) coating step performed with a commercial microwave, the wettability of the PU sponge was transformed from a hydrophilic state to a hydrophobic state
In the first step of the modification process, ZnO was grown on the original PU sponge to afford a PU@ZnO sponge

Summary

Introduction

With the increasing use of fossil fuel and the global population growth, oil spill accidents occurring during oil utilization and transport processes have adversely impacted the environment. Our relevant literature survey revealed that an increasing number of studies with the topics of “oil-water separation” and “superhydrophobic surface” were published from 2007 to 2016 (Fig. S1) This clearly demonstrates the focus of investigations on durable superhydrophobic materials for application to the proper separation of oil and water and the clean-up of spilled oils. The hydrophobicity was first derived from the microstructure, which was grown on the initial surface and was similar to that observed on the natural surface of Ramee leaves or Chinese watermelon For this first approach towards engineering a suitable surface roughness, a zinc oxide (ZnO) coating layer was selected due to its superior abilities, which include controlled of structure growth, low cost and environmental non-toxicity[15,23]. Because of its robust superhydrophobicity and good mechanical stability, the as-prepared PU@ZnO@Fe3O4@SA sponge ranks as a promising material for practical application to the sorption and recovery of oil from water

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Conclusion