Co-axial electrospun hollow MgO nanofibers for efficient removal of fluoride ions from water

Abstract

Porous and hollow metal oxide nanomaterials receive more attraction towards adsorption of various contaminates from water due to extremely high surface area. Co-axial electrospinning is an advance method to easily fabricate long length hollow nanotubes/nanofibers. Herein, hollow MgO nanofibers were synthesized using co-axial electrospinning method followed by post annealing. The co-axial electrospinning was performed by maintaining applied voltage (15 kV), needle tip to collector distance (12 cm) and flow rate of core and shell solutions (0.3 and 0.5 mL/h respectively). The formation, morphologies, bonding and surface area of the prepared nanofibers was analysed by XRD, FESEM, TEM and BET analytical techniques. The inner pore diameter of hollow MgO nanofibers was 32 nm. The surface area was found to be 527 m2/g which is much higher as compared to solid MgO nanofibers. The prepared hollow MgO nanofibers were used for the adsorption of fluoride ions from water. The effect of dose, contact time, pH and concentration were analysed. The fluoride adsorption process follows Pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity of hollow MgO was found to be 294 mg/g which is almost three-time greater than that of solid MgO nanofibers (92 mg/g). All the co-existing ions have showed negligible effect on fluoride adsorption except CO32- and PO43- ions. The adsorption energy of fluoride adsorbed MgO was calculated. The adsorption energy is found to be − 6.9004 eV. The negative value of adsorption energy indicates the feasibility of adsorption process.