Removal of Ferromagnetic Metals for the Large-Scale Purification of Single-Walled Carbon Nanotubes

An effective method has been developed to remove ferromagnetic metals for the large scale purification of single-walled carbon nanotubes (SWNTs) produced by arc-discharge, which are generally regarded as the most challenging soot to remove metallic catalyst residues. The efficiency of the method has been evaluated by electron microcopy, magnetic and thermogravimetric analysis. As a result, at least 200 mg SWNTs with 99% purity were obtained from 3.6 g raw soot. The metal percentage dropped from similar to 24.0% to similar to 1.0% and the magnetic metal percentage in the purified sample was as low as 0.2 wt %. Nearly all ferromagnetic metals were eliminated from the process.