Fabrication of pristine‑multiwalled carbon nanotubes/cellulose acetate composites for removal of methylene blue

Here, we report the effect of mixing different amounts of pristine-multiwalled carbon nanotubes (p-MWCNTs) with the cellulose acetate (CA) on dye removal. The p-MWCNTs loadings of the composites were varied from 0 to 1.0 wt%, and the non-solvent-induced phase separation methodology was used to fabricate the composite membranes, which were extensively characterized. The rheological tests confirmed that with 1.0 wt% of p-MWCNTs there was a classical filler effect in the viscoelastic behavior of the composite solution, but with no percolation of CNTs. The ATR-FTIR spectra identified specific interactions between CNTs and acetate groups of CA. SEM images showed a top dense layer sustained by a porous support layer consisting of a sponge-like structure in the middle layer. Aggregates of CNTs were seen at higher loadings of CNTs (> 0.1 wt%). The XRD diffractograms of composite membranes showed peak shifts compared to CA membranes due to the presence of CNTs into the CA structure, and their thermal stability was effective up to 320 °C. From the water permeability experiments, the calculated values of the membrane hydraulic resistance (R m ) of the composites were higher since a dense top layer and reduced pore size were achieved. Among all the composite membranes, M7 and M8 had the most desirable antifouling properties due to the high surface hydrophilicity imparted by the CNTs, and also showed an improvement in the removal of methylene blue (MB).M. Silva acknowledges funding for this study through an Individual postdoctoral grant from Fundacao para a Ciencia e a Tecnologia (PROJECT UID/CTM/00264/2013). L. Hilliou thanks the Fundacao para a Ciencia e a Tecnologia (FCT) for an Investigator contract (IF/00606/2014). The authors thank to NECL (Network of Extreme Conditions Laboratory, IFIMUP, Porto, Portugal) for the XRD measurements and SEMAT (UMinho, Guimaraes, Portugal) for SEM analysis. Besides, Dr. Silva acknowledges Professor I. Escobar and Dr. P. Wagh from University of Kentucky, USA, for proof reading and helpful discussions