Systematic hydrolysis of PIM-1 and electrospinning of hydrolyzed PIM-1 ultrafine fibers for an efficient removal of dye from water

Abstract

In this study, the Polymer of Intrinsic Microporosity (PIM-1) was systematically hydrolyzed in the presence of sodium hydroxide by varying the concentration of base, washing procedure and the time of the reaction. The chemical structure analyses confirmed that PIM-1 could be hydrolyzed by 65% up to 99% conversion depending on the synthesis procedure. The hydrolyzed PIM-1 samples have shown improved solubility which facilitates the fabrication of hydrolyzed PIM-1 ultrafine fibers by electrospinning technique. Extensive optimization studies were performed for the electrospinning of uniform and bead-free fibers from hydrolyzed PIM-1 with different degree of hydrolysis (65%, 86%, 94% and 99%). The electrospun hydrolysed PIM-1 fibrous samples have average fiber diameters (AFD) ranging from 0.58 ± 0.15 μm to 1.21 ± 0.15 μm, depending on the polymer concentration and applied electrospinning parameters. After electrospinning, self-standing hydrolyzed PIM-1 fibrous membranes were obtained which is useful as a filtering material for the adsorption of organic dyes from wastewater. Here, the capability of hydrolyzed PIM-1 electrospun fibrous membranes for the removal of dyes from aqueous solutions was investigated by using a batch adsorption process. The maximum adsorption capacity of fully hydrolyzed PIM-1 fibers was found 157 ± 16 mg g − 1 for Methylene Blue and 4 mg g − 1 for Congo red when the adsorption was conducted by 20 mg L − 1 dye solution without using any dilution. Moreover, maximum dye adsorption was also studied by using concentrated Methylene Blue solutions showing up to 272 mg g − 1 adsorption maximum. In addition, the self-standing fibrous hydrolyzed PIM-1 membrane was employed to separate Methylene Blue from an aqueous system by filtration without the necessity of additional driving force. The results indicate that hydrolyzed PIM-1 electrospun nanofibrous membranes can be a promising filtering material for wastewater treatment

Fabrication of Thermally Crosslinked Hydrolyzed Polymers of Intrinsic Microporosity (HPIM)/Polybenzoxazine Electrospun Nanofibrous Membranes

“…As‐electrospun and thermally treated HPIM NFM shows no difference in DSC, they both give two endothermic peaks at 158 and 218 °C. The first one is possibly relaxation of the polymer chains as we investigated in detail in our previous study and that was not a T g . The second one (218 °C, T d ) is the degradation of the polymer.…”

“…Structural characterization of parent PIM‐1 polymer was performed in our previous studies . 1 H‐NMR and FT‐IR spectra, and TGA curve of PIM‐1 are provided in Figures S1–S3, Supporting Information.…”

“…Electrospinning of HPIM was performed based on our previous study . Homogenous solutions of the HPIM and blend solutions of HPIM/(BA‐a) were prepared in DMF.…”

“…Hydrolysis of PIM‐1 was achieved according to previously described method . PIM‐1 powder was mixed with NaOH solution (water/ethanol: 1/1, v / v ) in a one‐neck round bottom flask which was fitted with a condenser.…”

“…PIM‐1 has nitrile groups in the backbone that can be modified by simple hydrolysis to tailor the properties of polymer for desired applications . Recently, we have reported electrospun‐hydrolyzed PIM‐1 (HPIM) NFM and its effective usage in methylene blue removal from an aqueous system since HPIM has an affinity toward cationic species . Despite the outstanding adsorption performance of HPIM, there is still room for improvement of the mechanical and chemical stability of this membrane.…”