Preparation of Carbon Nanotubes/Polyurethane Hybrids as a Synergistic Absorbent for Efficient Oil/Water Separation

Polyurethane (PU) hybrid materials have attracted a great deal of attention as oil-absorbents in oil/water separation because they combine the surface properties of nanomaterials and the excellent absorption properties of PU. Herein, we report a facile two-step process to synthesize the oil-absorbing hybrid materials by integrating carbon nanotubes (CNTs) into porous PU foam architectures. First, the multi-walled carbon nanotubes (MWCNTs) were modified by oxidation in binary H₂SO₄-HNO₃ mixed acid, followed by grafting the silane coupling agent (KH 570) on the on surfaces of MWCNTs. Then, the MWCNTs/PU hybrid materials were synthesized using isocyanate and polyether polyol as monomers for polymerization and surface modified MWCNTs as inorganic components. The physical and chemical properties of hybrid materials were validated by XRD, TEM, SEM, N₂ sorption and contact angle analysis. The surface grafted MWCNTs possess superhydrophobic properties with the maximum water contact angle of 153°. The SEM results indicate that the WCNTs/PU hybrid materials consisted of spherical structures with microscale holes, which can separate oils from oil/water mixtures with high absorption properties and high selectivity. Effects of the various MWCNTs contents on the oil absorption behavior of the WCNTs/PU hybrid materials were investigated. The results show that the modified MWCNTs significantly improves the oil absorption properties with the optimal MWCNTs content of 3 %. By combining the structural features of WCNTs and PU foams, the hybrid materials not only exhibit excellent absorption properties for various types of oils and organic solvents, but also show excellent oil recoverability and absorbent regenerability. The as-synthesized WCNTs/PU hybrid have significant potential as oil absorbents for efficient separation of oils and organic solvents from water.