A strategic approach towards thermal crosslinking of the electrospun PVA membrane using o -phenylene diamine: Superhydrophilic platform to grow PANI for simultaneous cationic and anionic dye rejections

This article endeavours the thermal crosslinking of electrospun polyvinyl alcohol (PVA) nanofiltration membrane using o -phenylene diamine (oPD) to avoid the excess solvent usage during the fabrication process. An exclusive analysis for the fabrication and crosslinking of the nanofiltration membrane was performed using response surface methodology (RSM) to achieve the highest insoluble fraction (Isf) for utilizing crosslinked PVA membrane in adsorption and filtration experiments. The optimized parameters were determined to be: crosslinker concentration of 0.56 % (w/v), temperature of 169 °C, crosslinking time of 9.9 h and membrane thickness of 264 μm. The Isf of the thermally crosslinked membrane under the optimized conditions was found to be 99.97 %. Interestingly, a very low quantity of 0.56 % oPD was enough to crosslink the high molecular weight PVA which could act as a stable superhydrophilic platform for the growth of PANI chains. The resulted information from the characterization studies like FTIR, XPS, FE-SEM, TGA, contact angle measurements and mechanical properties supported the successful crosslinking of PVA by oPD and coating of PANI. Comparative investigations were performed for the uncoated PVA nanofiltration membrane (UNM) and PANI coated PVA nanofiltration membrane (PNM) in the adsorption studies for the removal of crystal violet (CV) and amido black 10B (AB) at different pH levels. It was found that UNM had the maximum adsorption capacity of 138.89 mg g −1 towards CV and PNM had 30.86 mg g −1 towards AB at pH 5 indicating a selective removal. The adsorption isotherms revealed that UNM followed Freundlich model while PNM followed Langmuir model. Finally, the membranes were subjected towards simultaneous filtration of CV and AB in which the UNM exhibited a low rejection of 48.7 % while the PNM unveiled a high rejection of 95.9 %. The regeneration of PNM was found to be highly effective than UNM up to three cycles that proved PNM to be an efficient membrane for dye rejections.