Ionic liquid-multi walled carbon nanotubes composite tablet for continuous adsorption of tetracyclines and heavy metals

As the new kind of adsorbent, a 0.15 g ionic liquid-multi walled carbon nanotubes (IL-MWCNTs) composite tablet was prepared for the continuous adsorption of tetracyclines (TCs) and heavy metal ions from their aqueous solutions for the first time. Benzothiazole ionic liquid ( N -butyl benzothiazole hexafluoroborate, [C 4 Bth][PF 6 ]) was found selective for these objects, which was loaded into MWCNTs before tabletting under 5–20 MPa. Preparation operation was easy and the optional magnetic core (0.6 mm × 8 mm) could make it revolve in solution stably for accelerating mass transfer. Then the novel composite tablet was comprehensively characterized by scanning electron microscopy, thermogravimetry , Zeta potential and spectral analysis. Afterwards, the effects of main factors on adsorption results were investigated. Under unoptimized conditions, the adsorption efficiency of TCs, Cr 6+ and Cu 2+ could reach 99.76%, 94.10% and 84.60% by single tablet, respectively. It was also found that the adsorbed TCs could enhance the subsequent adsorption of copper ions . The experimental data fit well with pseudo-second-order model and Langmuir model (R 2  ≥ 0.99). By elution with 5 mol/L NaOH solution, the newly prepared composite tablet could be recycled and more than 90% adsorbate could be removed.