Enhanced heavy metals removal by a novel carbon nanotubes buckypaper membrane containing a mixture of two biopolymers: Chitosan and i-carrageenan

Abstract

Although existing membrane filtration technologies offer practical solutions for the removal of heavy metal ions from wastewater, there remains a great need for the realization of a membrane simultaneously possessing excellent selectivity, high permeability, and antifouling capability. Towards this end, novel buckypaper (BP) membranes were fabricated from multi-walled carbon nanotubes (MWCNTs) via vacuum filtration technique and the capability of two biopolymers (i.e. chitosan and carrageenan) to facilitate the formation of aqueous dispersions of MWCNTs was investigated alone and in combination of each other. For the first time, this study shows that the combination of BP membrane and both biopolymers (MWCNTs/chitosan-carrageenan) performs remarkably in terms of mechanical properties and high rejection of heavy metals. At an applied pressure of one bar, the removal of copper and lead reached 94% and 91%, respectively. The MWCNTs/chitosan-carrageenan membrane was also found to be mechanically robust, with a tensile strength and Young’s modulus of 30.69 ± 2.6 MPa and 3.78 ± 0.03 GPa, respectively. However, the MWCNTs/chitosan membrane showed superior water permeate flux, reaching up to 180 L/h.m2. The morphological properties and surface area (193 ± 3 to 285 ± 5 m2/g) of the three membrane types were also characterized using scanning electron microscopy and Brunauer, Emmett, and Teller analysis.