Carbon nanotubes grafted with β-cyclodextrin by an ultrasonication method and its demulsification performance in oily wastewater

Abstract

Emulsified oily wastewater has caused many problems in industrial production and ecological environment. To address this challenge, carbon nanotubes grafted with β-cyclodextrin (MCNT@β-CD) was prepared by an ultrasonic method to break oily wastewater. The composite materials were characterized by Fourier transform infrared spectroscopy, UV-visible spectroscopy, scanning electron microscope and thermogravimetric analysis. The demulsification test showed that the light transmittance of the resulting water phase was up to 94.5% at a low concentration of 50 mg/L within a few minutes at room temperature. Also, the corresponding oil remove rate was about 99.76%. In addition, it was suitable for acidic and neutral conditions with good salt tolerance. Interfacial activity, wettability, self-assembly at oil/water interface (WOI), dynamic interfacial tensions, zeta potential and photomicrograph were further investigated to confirm the possible mechanism. Generally speaking, the surface wettability of carbon nanotubes could be turned with β-CD. Therefore, MCNT@β-CD might rapidly migrate to WOI and replace the asphaltenes by π–π interactions and reduce the emulsion stability by charge neutralization. The current work provides a significant understand for the demulsification mechanism and indicates that MCNT@β-CD is a favorable interfacial activity, high demulsification efficiency and non-toxic demulsifier for oily wastewater.