Fabrication Of Polyacrylonitrile Nanofibrous Mats And Aerogels For Heavy Metal Adsorption

Electrospun nanofibrous mats have been a favorable substrate for preparing various nanomaterials owing to the three-dimensional structure,light weight,high porosity,high specific surface area and easy surface functionalization.The prepared nanomaterials can not only take full advantages of the surface effects of electrospun nanofibers,but also can enhence some properties for expanding its application.In this paper,polyacrylonitrile(PAN),a kind of polymer,was selected as the main material to fabricate the novel composite nanomaterials with coexisted fibers/nanospheres and porous fiber-based aerogels,combining electrospinning technology with electrospraying,homogenization and low-temperature freeze-drying technology.Thus,the as-prepared products were characterized by modern analytical techniques.Then we explored the application prospect of this composite nanomaterials in the adsorption of heavy metals,and investigated the preparation method of porous fiber-based aerogels.The main research contents and conclusions involved in this study are as follows:(1)we adopted CS containing amine groups and PAN including modified amine groups as raw materials to fabricate PAN-CS composite mats successfully via shoulder-to-shoulder electrospinning and electrospraying techniques,which could eliminate the obstacle of selecting a co-solvent system for dissolving PAN and CS together.The PAN nanofibers in the composite membrane were then chemically modified to produce a composite adsorbent with more amine groups.The prepared composite adsorbent was put into Pb(NO3)2 solution for multi-batch adsorption experiments to explore its adsorption performance for Pb2+.According to the results of the adsorption experiments,the maximum adsorption capacities of PAN-CS,PAN-CS/REC and APAN-CS/REC mats were 77.40 ± 4.5 mg/g,162.95 ± 8.6 mg/g and 500.95 ± 21.4 mg/g,respectively.Besides,APAN-CS/REC mats always performed high adsorption capacity with pH ranging widely from 2.0 to 6.5,which reflected its potential application in complex environments.All the results confirmed that both the incorporation of REC and the amination process could increase the adsorption performance of the adsorbents for lead ions.(2)Polyacrylonitrile(PAN)and polyvinylpyrrolidone(PVP)are used as initial materials to prepare PAN porous short-fiber dispersion by combining electrospinning technique and homogenization technique..PVP was eluted with Ethanol,then a rough and porous PAN short-nanofibers was prepared.With the good dispersibility and high specific surface area of porous short-fibers in the solution,PAN porous short fibers were more conducive to be aminated,then APAN porous short-fiber aerogels were fabricated by freeze-dried technique.It was found that the higher concentration of short-fiber in solution would make the denser fiber-network structure in the resulting aerogel.Finally,the cross-linking treatments can ameliorate the fragile defects of the aerogel,because they can form the chemical bonding action among the independently dispersed fibers to obtain the integral aerogels after the chemical cross linking.The as-prepared aerogels were applied for Cu2+ adsorption.The results showed that 10 mg/mL aerogel presented the highest adsorption capacity(83.21±2.2 mg/g)with the pH value of 4.5.The fabrication of nanoporous fibrous aerogels is a beneficial supplement to nanomaterials derived from electrospinning nanofibers substrates.