Removal of rhodamine 6G from aqueous solution in a continuous mode using nano-micro composite membranes

• PA6-nfs and PAN-nfs were fabricated by electrospinning technique. • The nanofibers/track-etched composite membranes were fabricated via an electrospinning process. • The composite membranes and the nanofibers were used for RD rejection from the solution in continuous flow mode. • PET-TMPAN had 99.57% rejection of 2 mg/L RD in an aqueous solution. This research presents the production of nanofibers, track-etched membrane, and nanofiber/track-etched composite membranes and their dye rejection studies. Polyamide 6 nanofibers (PA6-nfs) and polyacrylonitrile nanofibers (PAN-nfs) were fabricated using an electrospinning technique. Their respective composites with the metalized track-etched polyethylene terephthalate film (PET-TM), PET-TMPA6, and PET-TMPAN were also fabricated via electrospinning. The membranes were characterized using HRSEM, TEM, BET, and TGA techniques. The rejection experiments were studied with respect to the pH and the concentration of rhodamine 6G (RD), as well as the flow rate of the system. The pH is the most significant parameter in the filtration system at higher dye concentrations. At pH 10, the rejection percentages of 10 mg/L RD were 91.27% for PET-TMPAN and 70.66% for PET-TMPA6 at a flow rate of 1 mL/min. Also, PAN-nfs, PA6-nfs, and PET-TM gave 65.97%, 36.80%, and 24.53%, respectively. The composite membranes have higher rejection capabilities in comparison to their respective nanofibers. The performance of PET-TMPAN at a lower flow rate of 0.5 mL/min showed that the RD rejection by PET-TMPAN increased by ≈5 percent (91.27 to 96.01). At a lower concentration of 2 mg/L (to simulate higher dilution in river water) and pH (5.6), PET-TMPAN had a 99.59% RD rejection. All the membranes were regenerated and reused. The composite membrane PET-TMPAN has the capability to remove RD at both higher (96.01%) and lower concentrations (99.59%) of RD at lower flow rate, thereby making the system applicable and easy to use in river water purification.