Fabrication and characterization of carboxylated and aminolated multiwalled carbon nanotube/polyethersulfone (PES) membranes for the removal of heavy metals from wastewater

In this work, polyethersulfone (PES) adsorbent comprising carboxyl- and amino-functionalized multi-walled carbon nanotubes (MWCNTs) was fabricated through phase inversion method. The obtained nanocomposite was characterized via Fourier transform infrared, thermogravimetric analysis and scanning electron microscopy to reveal the effect of the presence of the functionalized carbon nanotubes on the properties of the obtained adsorbent. The acquired results not only confirmed the presence of the functionalized nanotubes in the nanocomposite structure, but also showed an improved hydrophilicity of the fabricated nanocomposite over bare PES membrane. Furthermore, equilibrium adsorption isotherms including Freundlich, Langmuir and Morris-Weber isotherms were employed to find the adsorption kinetics of the membrane and thus evaluate the adsorption efficiency of the product. The equilibrium sorption capacity was measured through pseudo-second order model, Langmuir and Freundlich isotherms by implementing the non-linear method. The Pb2+ adsorption capacity of 35, 65, 74, and 87 wt% was observed for bare PES, PES/MWCNTs, PES/carboxylated MWCNTs and PES/aminolated MWCNTs nanocomposites, respectively. These results indicate that it is possible to increase the heavy metal adsorption capacity of PES membranes up to ~2.5 times by the addition of functionalized MWCNTs.