Removal of anionic azo dyes from aqueous solution using magnetic polymer multi-wall carbon nanotube nanocomposite as adsorbent

•MPMWCNT was composed of ferroferric oxide, ionic liquid-based polyether and multi-wall carbon nanotubes.•MPMWCNT effectively removes color from dye-containing wastewater.•MPMWCNT has high adsorption capacity and fast adsorption rate.•Nanocomposite can be easily separated from the water by external magnetic field.•Adsorption of anionic azo dyes onto nanocomposite was favored at low pH. An adsorbent of magnetic polymer multi-wall carbon nanotube (MPMWCNT) nanocomposite was synthesized, which was composed of multi-wall carbon nanotubes, poly(1-glycidyl-3-methylimidazolium chloride) (ionic liquid-based polyether) and ferroferric oxide. The properties of MPMWCNT were investigated by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. The adsorptive capacity of MPMWCNT was examined using anionic azo dyes of orange II, sunset yellow FCF and amaranth as adsorbates. The effect of pH value was investigated and the adsorption kinetics and isotherms were also studied. It was found that a low pH value favors the adsorption of those anionic azo dyes and the adsorption kinetics and isotherms were well fitted by a pseudo second-order model and Langmuir model, respectively. The introduction of ionic liquid-based polyether and ferroferric oxide moieties into the multi-wall carbon nanotubes brings significant improvements in the adsorption and separation performance.