Mesoporous MgO/PPG hybrid nanofibers: synthesis, optimization, characterization and heavy metal removal property

In this research, mesoporous magnesium oxide/poly(propylene glycol) (MgO/PPG) hybrid nanofibers were synthesized as a new adsorbent for the removal of heavy metal ions from solutions. To do this, firstly, mesoporous MgO nanofibers were prepared using an electrospinning technique. Then, a polymeric layer containing PPG was deposited onto the surface of the MgO nanofibers. The aim was to produce hybrid nanofibers with a mesoporous structure, thus, the amount of the PPG containing layer was optimized. The characteristic analyses showed a high specific surface area value (185 m(2) g(-1)) even after the deposition of the polymeric layer. Although the mean mesopore size on the nanofiber surface was decreased, the size of the pores existing among the nanofibers increased because of the increasing nanofiber diameter. The average thickness of the polymeric layer was 7 nm. An investigation of the topography of the nanofibers revealed that the average surface roughness values increased after the deposition of the polymeric layer. The effect of operational parameters including adsorbent dosage, pH and initial metal ion concentration in the adsorption process was investigated. The results showed that the maximum adsorption capacity occurs at a pH of 7.5. The isotherm and kinetics of the adsorption process were evaluated using a non-linear regression method. To determine the best fit model for each system, three error functions were used. The results showed that the experimental data followed a Langmuir isotherm. Although the intra-particle diffusion was influenced by adsorption rate, the adsorption kinetic conformed to the pseudo-second order kinetic model. The regeneration experiment of nanofibers showed that the adsorption capacity for cadmium, copper and lead was as high as 1900.05, 1919.28 and 1922.79 mg g(-1) after seven cycles, respectively.