Multi-walled Carbon Nanotubes Grafted by Polyvinyl Alcohol and Its Demulsification Performance in Oily Wastewater

Multi-walled carbon nanotubes grafted by polyvinyl alcohol (CNTs@PVA) were synthesized via free radical reaction process under ultrasonic condition and used in oily wastewater for the demulsification. FT-IR, UV-Vis, SEM and TGA were employed to characterize the as-prepared CNTs@PVA. The demulsification performance in oily wastewater was estimated by bottle test. When the CNTs@PVA dosage was 80 mg/L, the light transmittance of separated water and the oil removal rate of the emulsions at room temperature for 30 min could reach 84.2% and 97.1%, respectively. In addition, the demulsification mechanism was systemically investigated by dynamic interfacial tension, interfacial activity, wettability, zeta potential and optical microscope. It suggested that PVA could tune the wettability of multi-walled carbon nanotubes by the surface modification. The change of the wettability is beneficial to the migration of CNTs@PVA to the oil-water interface, and accelerate the coalescence of oil droplets. The current finding provides a new non-toxic and high efficiency demulsifier for the oily wastewater.