| With the rapid development of the industry, the problem of heavy metal pollution is getting worse, so it is of great significance to do research on the technology to control the heavy metal pollution efficiently and rapidly. Nano-chelating fiber is a new kind of adsorption materials of heavy metal ions, which has been widely researched due to the unique advantages such as higher specific surface area and porosity, fast adsorption rates and good reproducibility.In this study, the spinnability of polymer with functional group of imino-acetic acid which was self-synthesized was studied. The influence of spinning conditions(voltage intensity, velocity and the distance between syringe needle and drum) on the morphology of nanofiber, and the effect of pre-crosslinking and crosslinking on the morphology, swelling and dissolution rate of nanofibers were also investigated. The adsorption performance such as thermodynamics and kinetics was discussed. The mainly results were given as follows:(1) The polymer with functional group of imino-acetic acid was self-synthesized, which could not be electrospinning if there was no other polymer. The spinnable solution was composed of PVA-1799, PVA-1788 and synthesized polymer. The spinning solution of 10wt% PVA-1799(A), 15wt% PVA-1788(B) and 30wt% synthesized polymer(C) with the mass ratio of A:B:C = 1:2:2 was the most feasible one.(2) The diameter of nanofibers was 150±77nm, when the optimized conditions of voltage 24 k V, working distance 8 cm, flowing rate 0.5 ml/h were applied.(3) The crosslinking reaction of nanofibers was studied. The optimized pre-crosslinking time of glutaraldehyde vapor at the temperature of 35℃ was 18 h; and the cross-linked nanofibers with the diameter of 250?99 nm without significantly change in morphology were harvested, while the crosslinking conditions were 20%(mass fraction) ECH solution, pH=3, crosslinking time of 4 h at the temperature of 40℃.(4) The infrared spectra of pre-crosslinking and crosslinked nano-fibers confirmed that the reactions of crosslinking were successful, and the dissolution ratio of as the electrospun and cross-linked nanofiber was 68.67% and 4.28%, respectively.(5) The adsorption experiments of nanofibers in simulated heavy metal pollution water showed that the pH was an important factor affecting the performance of nanofibers, and the optimized pH value for adsorption was 3.0 for copper ion, 5.5 for lead ion, respectively.(6) The adsorption dynamics of nanofibers for Cu(II) and Pb(II) obeyed pseudo-second-order model, and kinetic studies showed that adsorption equilibrium time was within 30 minutes for copper ion and 50 minutes for lead ion when initial concentration of metal ion in solution was 50mg/L at pH 3.0 for Cu(II), 5.5 for Pb(II), respectively.(7) The adsorption capacity of nanofibers increased with the initial concentration of metal ions although the sorption percentage reduced. The adsorption for Cu(II) and for Pb(II) onto nanofibers was fitted particularly well with Langmuir model. Furthermore, the sorption percentage of nanofibers increased when temperature was elevated, in which the maximum sorption percentage of the metal ions could reach 93.08% for Cu(II) and 96.69% for Pb(II) at the temperature of 40℃, respectively.(8) It was shown that sorption percentage could still reach about 90% for both Cu(II) and Pb(II) adsorption of their initial sorption percentage value after five adsorption/desorption cycles, this results implied that the imino-acetic acid type nanofibers has good recycling performance. |
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