Biomimetic functionalization of carbon nanotubes with poly(ionic liquids) for highly efficient adsorption of organic dyes

Abstract

The removal of environmental pollutants from wastewater through adsorption has regarded as one of the most efficient methods. A number of adsorbents based on nanomaterials and their composites have been examined for this purpose. Among them, carbon nanotubes (CNT) should be one of the promising candidates owing to their small size, large π conjugation system and high specific surface areas, however, the performance of CNT for adsorption is largely impeded by their poor dispersibility and lack of functional groups. Therefore, the development of simple and effective surface modification strategies to overcome the above drawbacks should be of great importance for their practical utilization in the environmental fields. In this study, a novel and simple biomimetic method was reported for the first time for surface modification of CNT with poly(ionic liquids) through the combination of mussel-inspired chemistry and subsequent surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization. An ionic liquid ([C16VIm+] [Br−]) was used as the monomer in this work because it is capable of introducing charged functional groups on the surface of CNT and thus boosts their adsorption performance towards environmental pollutants. As a model organic dye, Congo red (CR) was selected as the environmental pollutant and its adsorption behaviors of CR by CNT@IL composites were examined and analyzed in details. The results demonstrated that the adsorption capacity of CNT@IL intake CR (50 mg L−1) was obvious higher than that of unmodified CNT and the adsorption capacity reaches 178 mg g−1 with pH = 7 at 56 min. In addition, adsorption kinetic models and isotherm models were investigated to identify the adsorption kinetic rates and adsorption behavior, respectively. The adsorption principle that including electrostatic interaction, π-π interaction between imidazole rings on the surface of CNT@IL and CR, was proposed. This novel biomimetic surface modification could also be utilized for fabrication of many other functional materials with designable properties and improved performance. Therefore, this work will open up a new research avenue for the fabrication of multifunctional CNT based polymer composites.