Preparation Of Polyacrylonitrile Chelating Nanofiber Membrane And Its Adsorption Performance

In the modern industry, the treatment of wastewater which contains heavy metal ions and dyes has become the theme of environmental protection, developing a kind of high-performance material of wastewater treatment is of great significance. Among different kinds of materials, the polyacrylonitrile(PAN) chelating nanofiber membrane with high surface area and excellent adsorption performance which is prepared by electrospinning has drawn more and more attention and showed great application prospect in the field of sewage treatment. In previous work, mostly based on the polyacrylonitrile nanofibers which were prepared by electrospping and then took a grafting reaction with the hydroxylamine hydrochloride(or ethylenediamine, diethylenetriamine, etc.) to obtained the chelating nanofibers membrane which had abilities of adsorption of Cu2+, Ag+, Pb2+ heavy metal ions and the abilities of adsorption had been raised several to dozens of times compared to the PAN chelate fibers came from a similar progress before. But it was found that after further study, along with the increase of the amount of hydroxylamine hydrochloride was introduced into grafting reaction, the membrane contraction significantly, flexible variation, strength reduced, became very fragile and easily broken, even out of use. In the meantime, the problem of process trival and inconvenient operation made development of flexible and process relatively simple polyacrylonitrile chelated nanofiber preparation method of great significance.In this context, we designed a simple method to modify the PAN via hydroxylamine hydrochloride or ethylenediamine, and then prepared the chelating nanofiber membrane by electrospinning. It was not only obtained the flexible fiber membrane, but also got continuous operation in the PAN grafting modification electrospinning, and avoided the inconvenience in the large fiber membrane for grafting reaction. Specific content as follows:1. The spinning solution(AOPAN) was prepared by hydroxylamine hydrochloride and polyacrylonitrile solution under alkali catalytic reaction, then electrospinning technique was used to prepare the amine oximation polyacrylonitrile chelated nanofiber membrane(AOPAN NFs)and the adsorption performance of the metal ions(copper, lead) and eight kinds of water-soluble dye were surveyed. The results showed that the process of AOPAN NFs on copper, lead metal ions and methyl orange dye were monolayer adsorption, the maximum adsorption quantity were145.77 mg.g-1、178.89 mg.g-1 and 77.45 mg.g-1 respectively. But the solution viscosity of amine oximation polyacrylonitrile spinning was not very stable and it would increase with the increase of placing time and finally crosslinking became gel. The problem above could possiblely cause the blocking in nozzles and the pipe lines in the mass continuous preparation and how to solve the problem was the key point of industrial application.2. The spinning solution with stable viscosity was prepared by cross-linked inhibition technology of AOPAN and the AOPAN NFs were prepared by electrospinning technology. It proved that with the addition of cross-linked inhibition, the place time of spinning solution was extended to more than 192 h with little viscosity change and the cross-linked inhibition could be removed from the AOPAN NFs after electrospinning. The AOPAN NFs still had the adsorption ability for heavy metal irons and dyes and the maximum adsorption quantity of copper iron, lead iron and methyl orange dye were 143.47 mg.g-1, 178.57 mg.g-1 and 68.07 mg.g-1 respectively.3. The amination polyacrylonitrile chelated nanofiber membrane(EDA-PAN NFs) was successfully synthesized via the method that ethylenediamine and polyacrylonitrile taking amination reaction and then spinning. It was surveyed that the adsorption performance of the EDA-PAN NFs for eight kinds of water-soluble dyes respectively. The study showed that EDA- PAN NFs had good adsorption capability for cationic dyes and the maximum adsorption quantity of safranine T and methylene blue were 77.46 mg.g-1 and 70.22 mg.g-1 respectively.