Removal of lead ion and oil droplet from aqueous solution by lignin-grafted carbon nanotubes

Water contamination is one of the most serious problems afflicting people throughout the world, innovation of nanomaterials with eco-friendliness is important for a greener environment. Here, an eco-friendly nanocomposite based on lignin grafted carbon nanotubes (L-CNTs) is reported as a new type of adsorbent for water remediation. By integrating the tridimensional structure, oxygen-containing functional groups and eco-friendliness of lignin with the high surface area and mechanical stability of CNTs, the as-prepared nanocomposite not only possesses a good water-dispersibility and eco-friendliness, but also exhibits an excellent adsorption capability for lead ion and oil droplet. It shows a high distribution coefficient for lead ion ( K d   =   3.6   ×   10 5   mL/g) that is comparable to some benchmark materials, including mesoporous carbon and metal-organic frameworks. The large surface area and tridimensional structure also endows L-CNTs with a high removal efficiency for oil droplet from water. Moreover, the cost of the nanocomposite has been minimized by incorporation of the low cost lignin. These results demonstrate the as-obtained nanocomposite with a natural polymer layer has advanced adsorption capability, low-in cost and eco-friendliness, and accordingly is an ideal candidate for water cleanup.