Water-Soluble Carbon Nanotubes from Bitumen Waste: Synthesis, Functionalisation and Derivatisation for its Use as Superabsorbent

A simple method for the preparation of carbon nanotubes (CNTs) from bitumen waste and their derivatisation with polyacrylamide was achieved. Synthesised CNTs were functionalised in the presence of dilute nitric acid followed by derivatisation with polyacrylamide using the mixture of potassium persulphate-ferrous ammonium sulphate as a redox initiator and N,N′-methylene-bis-acrylamide as a crosslinking agent. The functionalisation and derivatisation of the CNTs were confirmed through Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. The effect of derivatisation on the thermal properties of the CNTs was studied by thermogravimetric analysis, differential thermogravimetric analysis and differential thermal analysis. The crosslinked derivatised product, CNT-cl-poly(AAm), was thermally more stable than the functionalised CNTs. The water-absorption capacity of the derivatised CNTs was investigated in deionised water as a function of time, temperature and pH of the swelling medium. CNT-cl-poly(AAm) was found to be an efficient water-absorption device with the maximum absorption capacity of 476 %.