(713h) Modified Polyacrylonitrile Nanofibers Membrane and Its Application in the Remediation of Dye Polluted Wastewater

In the present work, electrospinning of polyacrylonitrile (PAN) to nanofibers (NFs) membrane, grafting of ethanolamine (EA) functional group to PAN NFs membrane (EA-g-PAN), and its application to the removal of dyes from the synthetic solution of dyes was studied. The membrane was characterized by field emission scanning electron microscopy (FE-SEM) and Fourier transforms infrared (FT-IR) spectroscopy. FE-SEM showed smooth morphology for NFs before and after grafting, whereas FT-IR confirmed the grafting of EA to the nitrile group of PAN. The % grafting value with no change in the physical nature (remained soft) for EA was 12.18 %. The nitrogen adsorption-desorption isotherms for PAN and EA-g-PAN were similar and according to IUPAC were classified as a type IV. This indicated relatively uniform cylindrical mesopores in the membranes with bimodal opening. Surface area, pore volume and pore size of the EA-g-PAN increased to 21.36 m².g^-1, 0.16 cm³/g and 304.93 A^O from 15.95 m².g^-1, 0.15cm³/g and 128.93 A^O for PAN. The adsorption of MB, RB and ST dyes from solution onto PAN and the EA-g-PAN NFs membranes showed that adsorption leveled off at ~ 60 min for all the dyes. The adsorption of all the dyes onto these membranes was found to increase in the order PAN<EA-g-PAN. This increase in the adsorption of the dyes with grafting could be attributed to the increased available surface and number of active sites onto the membranes. Adsorption kinetics data showed good fitting to the pseudo-second-order model with a multi-steps diffusion process. The adsorption data for the dyes fitted well to Langmuir and Freundlich models. The value of the correlation coefficient (r²) for Langmuir varied from 0.940 to 0.995 and for Freundlich from 0.941 to 0.998. The slightly increased values of the correlation coefficient in the case of Freundlich suggested that along with monolayer formation some condensation (physical adsorption) of dyes has also occurred onto the NFs membranes. FT-IR spectra did not show any real chemical interactions between the dyes and membrane after adsorption (due to the complex nature of the dyes), only broadening of the bands were observed due to hydrogen bonding.