Abstract
This study investigated adsorption kinetics, adsorption equilibrium, and adsorption isotherm of three dyes [i.e., methylene blue (MB), rhodamine-B (RB), and safranin T (ST)] onto polyacrylonitrile (PAN) and ethanolamine (EA) grafted PAN nanofibers (NFs) membranes (EA-g-PAN). The membranes were characterized by field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR) spectroscopy, and Brunauer-Emmet-Teller (BET). FE-SEM showed a smooth morphology for the NFs before and after grafting, while FT-IR confirmed EA grafting into the nitrile group of PAN. The grafting percentage with no change in the physical nature of the membrane was 12.18%. The nitrogen adsorption-desorption isotherms for PAN and EA-g-PAN NFs membranes were similar and classified as a Type IV according to the International Union of Pure and Applied Chemistry. The surface area, pore-volume, and pore size of the EA-g-PAN increased to 21.36 m(2) g(-1), 0.16 cm(3) g(-1), and 304.93 angstrom, respectively. The pores were cylindrical mesopores with bimodal openings, which means that pores were open at both ends. The adsorption of the MB, RB, and ST dyes onto the PAN and EA-g-PAN NFs membranes leveled off at similar to 60 min. The adsorption kinetics showed good fitting to pseudo-second-order kinetic model and multi-step diffusion process. The order of the dye adsorption was PAN < EA-g-PAN. The data were fitted to Langmuir and Freundlich models. The correlation coefficient (r(2)) for Langmuir ranged from 0.940 to 0.995, whereas that for Freundlich ranged from 0.941 to 0.998. After adsorption, FTIR only showed hydrogen bonding between the dyes and the membrane. The reusability experiments showed max desorption for MB (94%), RB (92%), and ST (85%). The EA-g-PAN NFs membrane showed potential for the removal of organic pollutants from the environment.