Hydroxylated α-Fe2O3 nanofiber: Optimization of synthesis conditions, anionic dyes adsorption kinetic, isotherm and error analysis

Abstract

In this paper, hydroxylated α-Fe2O3 nanofiber was synthesized by the combination of electrospinning method and in-situ polymerization and its potential for the adsorption of cationic dyes was investigated. The vinyl acetate monomer was polymerized onto the surface of α-Fe2O3 nanofiber and subsequently it was hydrolyzed in an alkaline solution to convert the acetate group to hydroxyl group. The optimized condition of polymerization was reported. The characteristics of nanofiber were investigated by Fourier transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FE-SEM), energy-dispersive X-ray (EDX) and Brunauer–Emmett–Teller (BET). The FTIR result confirmed successful polymerization of vinyl acetate and generation of hydroxyl group on the surface. Microscopic analyses revealed that the modified nanofiber has a long continuous structure because of attaching the adjacent silanol group of nanofibers. Also, decreasing in the total surface area of nanofiber was detected by BET analysis. Furthermore, the influence of parameters affecting on dye removal such as adsorbent dosage, initial dye concentration and pH was investigated. The mechanism and rate of adsorption were evaluated by different adsorption isotherm and kinetic models. Non-linear regression was used to determine the best fit model for each system. To do this, three error functions were applied to predict the optimum model. It was found that the adsorption of dyes onto hydroxylated nanofiber is based on Langmuir isotherm and pseudo-second-order kinetic model.