Evaluation of residual iron in carbon nanotubes purified by acid treatments

► We produced multi-walled carbon nanotubes powder by pyrolysis of camphor mixed with ferrocene, and then used non-oxidative and oxidative acidic treatments for iron removal. ► We analyzed the elimination and/or oxidation of iron nanoparticles by X-ray photoelectron spectroscopy, monitoring Fe2p, O1s and C1s peaks. ► We carried out complementary investigation by thermogravimetric analysis, atomic absorption spectroscopy, Raman Spectroscopy and transmission electron microscopy (TEM) to evaluate the effectiveness of each treatment. ► A purity degree higher than 98% was achieved only with non-oxidative treatments using sonification process.