Lignin-assisted double acoustic irradiation for concentrated aqueous dispersions of carbon nanotubes

The full potential of carbon nanotubes (CNTs), one of the most widely used nanomaterials to date, still remains to be realized, and the dispersion of CNTs is one of the main challenging tasks for many practical applications. Lignin, one of the most abundant renewable polymers, has recently been investigated as a potential dispersant to prepare CNT suspensions. The present study provides a benchmark of the effectiveness of lignin in dispersing CNTs compared to typical petrochemical surfactants. Aqueous dispersions of CNTs are characterized by UV-vis spectroscopy, optical, and electronic microscopy. The influence of dispersant concentration, sonication energy, surfactant mixtures, CNT morphology and oxidation are thoroughly examined. The use of a double acoustic irradiation system combining both bath and probe sonication is also investigated as a promising way to improve dispersion quality and reduce processing time. Results demonstrate that lignin-assisted double sonication represents a major low-cost and renewable alternative to prepare stable and concentrated suspensions of individualized CNTs.