Microwave-induced synthesis of β-cyclodextrin/N-doped carbon nanotube polyurethane nanocomposites for water purification

The fabrication of polymer nanocomposites for the removal of organic species in aqueous media is achieved using conventional methods. However, these methods are expensive and deteriorating to the environment due to high energy demands and high organic solvent volume requirements. This work discusses the synthesis of nanocomposite polymers of β-cyclodextrin (β-CD) and nitrogen-doped carbon nanotubes (N-CNTs) under microwave irradiation for the first time. This novel method is efficient, greener and time saving. Typically, the reaction to prepare β-CD polymers takes about 24 h. Here we report a novel method to synthesize the polymers in 10 min. N-CNTs were synthesized via chemical vapour deposition method (CVD) using a 10 wt% Fe–Co/CaCO3 catalyst. The N-CNTs were found to contain ∼2 at% nitrogen by CN analysis. The N-CNTs were of high purity and were oxidized with acid functional groups (–COOH, –CO, –OH) using nitric acid under reflux. Zeta potential studies indicated that the quantity of acid functional groups increases with increase in acid treatment times. The functionalised N-CNTs (fN-CNTs) were then polymerized with β-CD using hexamethylene diisocyanate as the functional cross-linker in a microwave under an inert gas atmosphere. The polymers showed an efficient removal of p-nitrophenol from spiked water samples as confirmed by UV–Vis spectroscopy.