Removal of oil droplets from contaminated water using magnetic carbon nanotubes

Haitao Wang, Kun Yi Lin, Benxin Jing, Galyna Krylova, Ginger E. Sigmon, Paul McGinn, Yingxi Zhu, Chongzheng Na

Research output: Contribution to journalArticlepeer-review

84 Scopus citations

Abstract

Water contaminated by oil and gas production poses challenges to the management of America's water resources. Here we report the design, fabrication, and laboratory evaluation of multi-walled carbon nanotubes decorated with superparamagnetic iron-oxide nanoparticles (SPIONs) for oil-water separation. As revealed by confocal laser-scanning fluorescence microscopy, the magnetic carbon nanotubes (MCNTs) remove oil droplets through a two-step mechanism, in which MCNTs are first dispersed at the oil-water interface and then drag the droplets with them out of water by a magnet. Measurements of removal efficiency with different initial oil concentration, MCNT dose, and mixing time show that kinetics and equilibrium of the separation process can be described by the Langmuir model. Separation capacity qt is a function of MCNT dose m, mixing time t, and residual oil concentration Ce at equilibrium:1qt=1qmax2kwm(1KCe+1)21t+1qmax(1KCe+1) where qmax, kw, and K are maximum separation capacity, wrapping rate constant, and equilibrium constant, respectively. Least-square regressions using experimental data estimate qmax=6.6(±0.6) g-diesel g-MCNT-1, kw=3.36(±0.03)Lg-diesel-1min-1, and K=2.4(±0.2)Lg-diesel-1. For used MCNTs, we further show that over 80% of the separation capacity can be restored by a 10min wash with 1mL ethanol for every 6mg MCNTs. The separation by reusable MCNTs provides a promising alternative strategy for water treatment design complementary to existing ones such as coagulation, adsorption, filtration, and membrane processes.

Original languageEnglish
Pages (from-to)4198-4205
Number of pages8
JournalWater Research
Volume47
Issue number12
DOIs
StatePublished - Aug 1 2013

Keywords

  • Energy and water security
  • Environmental nanotechnology
  • Fossil fuels
  • Industrial wastewater
  • Pickering emulsion
  • Responsive nanocomposite

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